Some further wording tweaks to additional documentation
[debian-policy.git] / policy.sgml
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1 <!doctype debiandoc system [
2 <!-- include version information so we don't have to hard code it
3 within the document -->
4 <!entity % versiondata SYSTEM "version.ent"> %versiondata;
5 <!-- current Debian changes file format -->
6 <!entity changesversion "1.8">
7 ]>
8 <debiandoc>
10 <book>
11 <titlepag>
12 <title>Debian Policy Manual</title>
13 <author><qref id="authors">The Debian Policy Mailing List</qref></author>
14 <version>version &version;, &date;</version>
16 <abstract>
17 This manual describes the policy requirements for the Debian
18 distribution. This includes the structure and
19 contents of the Debian archive and several design issues of
20 the operating system, as well as technical requirements that
21 each package must satisfy to be included in the distribution.
22 </abstract>
24 <copyright>
25 <copyrightsummary>
26 Copyright &copy; 1996,1997,1998 Ian Jackson
27 and Christian Schwarz.
28 </copyrightsummary>
29 <p>
30 These are the copyright dates of the original Policy manual.
31 Since then, this manual has been updated by many others. No
32 comprehensive collection of copyright notices for subsequent
33 work exists.
34 </p>
36 <p>
37 This manual is free software; you may redistribute it and/or
38 modify it under the terms of the GNU General Public License
39 as published by the Free Software Foundation; either version
40 2, or (at your option) any later version.
41 </p>
43 <p>
44 This is distributed in the hope that it will be useful, but
45 <em>without any warranty</em>; without even the implied
46 warranty of merchantability or fitness for a particular
47 purpose. See the GNU General Public License for more
48 details.
49 </p>
51 <p>
52 A copy of the GNU General Public License is available as
53 <file>/usr/share/common-licenses/GPL</file> in the Debian
54 distribution or on the World Wide Web at
55 <url id="http://www.gnu.org/copyleft/gpl.html"
56 name="the GNU General Public Licence">. You can also
57 obtain it by writing to the Free Software Foundation, Inc.,
58 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
59 </p>
60 </copyright>
61 </titlepag>
63 <toc detail="sect1">
65 <chapt id="scope">
66 <heading>About this manual</heading>
67 <sect>
68 <heading>Scope</heading>
69 <p>
70 This manual describes the policy requirements for the Debian
71 distribution. This includes the structure and
72 contents of the Debian archive and several design issues of the
73 operating system, as well as technical requirements that
74 each package must satisfy to be included in the
75 distribution.
76 </p>
78 <p>
79 This manual also describes Debian policy as it relates to
80 creating Debian packages. It is not a tutorial on how to build
81 packages, nor is it exhaustive where it comes to describing
82 the behavior of the packaging system. Instead, this manual
83 attempts to define the interface to the package management
84 system that the developers have to be conversant with.<footnote>
85 Informally, the criteria used for inclusion is that the
86 material meet one of the following requirements:
87 <taglist compact="compact">
88 <tag>Standard interfaces</tag>
89 <item>
90 The material presented represents an interface to
91 the packaging system that is mandated for use, and
92 is used by, a significant number of packages, and
93 therefore should not be changed without peer
94 review. Package maintainers can then rely on this
95 interface not changing, and the package management
96 software authors need to ensure compatibility with
97 this interface definition. (Control file and
98 changelog file formats are examples.)
99 </item>
100 <tag>Chosen Convention</tag>
101 <item>
102 If there are a number of technically viable choices
103 that can be made, but one needs to select one of
104 these options for inter-operability. The version
105 number format is one example.
106 </item>
107 </taglist>
108 Please note that these are not mutually exclusive;
109 selected conventions often become parts of standard
110 interfaces.
111 </footnote>
112 </p>
115 The footnotes present in this manual are
116 merely informative, and are not part of Debian policy itself.
117 </p>
120 The appendices to this manual are not necessarily normative,
121 either. Please see <ref id="pkg-scope"> for more information.
122 </p>
125 In the normative part of this manual,
126 the words <em>must</em>, <em>should</em> and
127 <em>may</em>, and the adjectives <em>required</em>,
128 <em>recommended</em> and <em>optional</em>, are used to
129 distinguish the significance of the various guidelines in
130 this policy document. Packages that do not conform to the
131 guidelines denoted by <em>must</em> (or <em>required</em>)
132 will generally not be considered acceptable for the Debian
133 distribution. Non-conformance with guidelines denoted by
134 <em>should</em> (or <em>recommended</em>) will generally be
135 considered a bug, but will not necessarily render a package
136 unsuitable for distribution. Guidelines denoted by
137 <em>may</em> (or <em>optional</em>) are truly optional and
138 adherence is left to the maintainer's discretion.
139 </p>
142 These classifications are roughly equivalent to the bug
143 severities <em>serious</em> (for <em>must</em> or
144 <em>required</em> directive violations), <em>minor</em>,
145 <em>normal</em> or <em>important</em>
146 (for <em>should</em> or <em>recommended</em> directive
147 violations) and <em>wishlist</em> (for <em>optional</em>
148 items).
149 <footnote>
150 Compare RFC 2119. Note, however, that these words are
151 used in a different way in this document.
152 </footnote>
153 </p>
156 Much of the information presented in this manual will be
157 useful even when building a package which is to be
158 distributed in some other way or is intended for local use
159 only.
160 </p>
163 udebs (stripped-down binary packages used by the Debian Installer) do
164 not comply with all of the requirements discussed here. See the
165 <url name="Debian Installer internals manual"
166 id="http://d-i.alioth.debian.org/doc/internals/ch03.html"> for more
167 information about them.
168 </p>
169 </sect>
171 <sect>
172 <heading>New versions of this document</heading>
175 This manual is distributed via the Debian package
176 <package><url name="debian-policy"
177 id="http://packages.debian.org/debian-policy"></package>
178 (<httpsite>packages.debian.org</httpsite>
179 <httppath>/debian-policy</httppath>).
180 </p>
183 The current version of this document is also available from
184 the Debian web mirrors at
185 <tt><url name="/doc/debian-policy/"
186 id="http://www.debian.org/doc/debian-policy/"></tt>.
188 <httpsite>www.debian.org</httpsite>
189 <httppath>/doc/debian-policy/</httppath>)
190 Also available from the same directory are several other
191 formats: <file>policy.html.tar.gz</file>
192 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
193 <file>policy.pdf.gz</file>
194 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
195 and <file>policy.ps.gz</file>
196 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
197 </p>
200 The <package>debian-policy</package> package also includes the file
201 <file>upgrading-checklist.txt.gz</file> which indicates policy
202 changes between versions of this document.
203 </p>
204 </sect>
206 <sect id="authors">
207 <heading>Authors and Maintainers</heading>
210 Originally called "Debian GNU/Linux Policy Manual", this
211 manual was initially written in 1996 by Ian Jackson.
212 It was revised on November 27th, 1996 by David A. Morris.
213 Christian Schwarz added new sections on March 15th, 1997,
214 and reworked/restructured it in April-July 1997.
215 Christoph Lameter contributed the "Web Standard".
216 Julian Gilbey largely restructured it in 2001.
217 </p>
220 Since September 1998, the responsibility for the contents of
221 this document lies on the <url name="debian-policy mailing list"
222 id="mailto:debian-policy@lists.debian.org">. Proposals
223 are discussed there and inserted into policy after a certain
224 consensus is established.
225 <!-- insert shameless policy-process plug here eventually -->
226 The actual editing is done by a group of maintainers that have
227 no editorial powers. These are the current maintainers:
229 <enumlist>
230 <item>Russ Allbery</item>
231 <item>Bill Allombert</item>
232 <item>Andreas Barth</item>
233 <item>Jonathan Nieder</item>
234 </enumlist>
235 </p>
238 While the authors of this document have tried hard to avoid
239 typos and other errors, these do still occur. If you discover
240 an error in this manual or if you want to give any
241 comments, suggestions, or criticisms please send an email to
242 the Debian Policy List,
243 <email>debian-policy@lists.debian.org</email>, or submit a
244 bug report against the <tt>debian-policy</tt> package.
245 </p>
248 Please do not try to reach the individual authors or maintainers
249 of the Policy Manual regarding changes to the Policy.
250 </p>
251 </sect>
253 <sect id="related">
254 <heading>Related documents</heading>
257 There are several other documents other than this Policy Manual
258 that are necessary to fully understand some Debian policies and
259 procedures.
260 </p>
263 The external "sub-policy" documents are referred to in:
264 <list compact="compact">
265 <item><ref id="fhs"></item>
266 <item><ref id="virtual_pkg"></item>
267 <item><ref id="menus"></item>
268 <item><ref id="perl"></item>
269 <item><ref id="maintscriptprompt"></item>
270 <item><ref id="emacs"></item>
271 </list>
272 </p>
275 In addition to those, which carry the weight of policy, there
276 is the Debian Developer's Reference. This document describes
277 procedures and resources for Debian developers, but it is
278 <em>not</em> normative; rather, it includes things that don't
279 belong in the Policy, such as best practices for developers.
280 </p>
283 The Developer's Reference is available in the
284 <package>developers-reference</package> package.
285 It's also available from the Debian web mirrors at
286 <tt><url name="/doc/developers-reference/"
287 id="http://www.debian.org/doc/developers-reference/"></tt>.
288 </p>
291 Finally, a <qref id="copyrightformat">specification for
292 machine-readable copyright files</qref> is maintained as part of
293 the <package>debian-policy</package> package using the same
294 procedure as the other policy documents. Use of this format is
295 optional.
296 </p>
297 </sect>
299 <sect id="definitions">
300 <heading>Definitions</heading>
303 The following terms are used in this Policy Manual:
304 <taglist>
305 <tag>ASCII</tag>
306 <item>
307 The character encoding specified by ANSI X3.4-1986 and its
308 predecessor standards, referred to in MIME as US-ASCII, and
309 corresponding to an encoding in eight bits per character of
310 the first 128 <url id="http://www.unicode.org/"
311 name="Unicode"> characters, with the eighth bit always zero.
312 </item>
313 <tag>UTF-8</tag>
314 <item>
315 The transformation format (sometimes called encoding) of
316 <url id="http://www.unicode.org/" name="Unicode"> defined by
317 <url id="http://www.rfc-editor.org/rfc/rfc3629.txt"
318 name="RFC 3629">. UTF-8 has the useful property of having
319 ASCII as a subset, so any text encoded in ASCII is trivially
320 also valid UTF-8.
321 </item>
322 </taglist>
323 </p>
324 </sect>
325 </chapt>
328 <chapt id="archive">
329 <heading>The Debian Archive</heading>
332 The Debian system is maintained and distributed as a
333 collection of <em>packages</em>. Since there are so many of
334 them (currently well over 15000), they are split into
335 <em>sections</em> and given <em>priorities</em> to simplify
336 the handling of them.
337 </p>
340 The effort of the Debian project is to build a free operating
341 system, but not every package we want to make accessible is
342 <em>free</em> in our sense (see the Debian Free Software
343 Guidelines, below), or may be imported/exported without
344 restrictions. Thus, the archive is split into areas<footnote>
345 The Debian archive software uses the term "component" internally
346 and in the Release file format to refer to the division of an
347 archive. The Debian Social Contract simply refers to "areas."
348 This document uses terminology similar to the Social Contract.
349 </footnote> based on their licenses and other restrictions.
350 </p>
353 The aims of this are:
355 <list compact="compact">
356 <item>to allow us to make as much software available as we can</item>
357 <item>to allow us to encourage everyone to write free software,
358 and</item>
359 <item>to allow us to make it easy for people to produce
360 CD-ROMs of our system without violating any licenses,
361 import/export restrictions, or any other laws.</item>
362 </list>
363 </p>
366 The <em>main</em> archive area forms the <em>Debian distribution</em>.
367 </p>
370 Packages in the other archive areas (<tt>contrib</tt>,
371 <tt>non-free</tt>) are not considered to be part of the Debian
372 distribution, although we support their use and provide
373 infrastructure for them (such as our bug-tracking system and
374 mailing lists). This Debian Policy Manual applies to these
375 packages as well.
376 </p>
378 <sect id="dfsg">
379 <heading>The Debian Free Software Guidelines</heading>
381 The Debian Free Software Guidelines (DFSG) form our
382 definition of "free software". These are:
383 <taglist>
384 <tag>1. Free Redistribution
385 </tag>
386 <item>
387 The license of a Debian component may not restrict any
388 party from selling or giving away the software as a
389 component of an aggregate software distribution
390 containing programs from several different
391 sources. The license may not require a royalty or
392 other fee for such sale.
393 </item>
394 <tag>2. Source Code
395 </tag>
396 <item>
397 The program must include source code, and must allow
398 distribution in source code as well as compiled form.
399 </item>
400 <tag>3. Derived Works
401 </tag>
402 <item>
403 The license must allow modifications and derived
404 works, and must allow them to be distributed under the
405 same terms as the license of the original software.
406 </item>
407 <tag>4. Integrity of The Author's Source Code
408 </tag>
409 <item>
410 The license may restrict source-code from being
411 distributed in modified form <em>only</em> if the
412 license allows the distribution of "patch files"
413 with the source code for the purpose of modifying the
414 program at build time. The license must explicitly
415 permit distribution of software built from modified
416 source code. The license may require derived works to
417 carry a different name or version number from the
418 original software. (This is a compromise. The Debian
419 Project encourages all authors to not restrict any
420 files, source or binary, from being modified.)
421 </item>
422 <tag>5. No Discrimination Against Persons or Groups
423 </tag>
424 <item>
425 The license must not discriminate against any person
426 or group of persons.
427 </item>
428 <tag>6. No Discrimination Against Fields of Endeavor
429 </tag>
430 <item>
431 The license must not restrict anyone from making use
432 of the program in a specific field of endeavor. For
433 example, it may not restrict the program from being
434 used in a business, or from being used for genetic
435 research.
436 </item>
437 <tag>7. Distribution of License
438 </tag>
439 <item>
440 The rights attached to the program must apply to all
441 to whom the program is redistributed without the need
442 for execution of an additional license by those
443 parties.
444 </item>
445 <tag>8. License Must Not Be Specific to Debian
446 </tag>
447 <item>
448 The rights attached to the program must not depend on
449 the program's being part of a Debian system. If the
450 program is extracted from Debian and used or
451 distributed without Debian but otherwise within the
452 terms of the program's license, all parties to whom
453 the program is redistributed must have the same
454 rights as those that are granted in conjunction with
455 the Debian system.
456 </item>
457 <tag>9. License Must Not Contaminate Other Software
458 </tag>
459 <item>
460 The license must not place restrictions on other
461 software that is distributed along with the licensed
462 software. For example, the license must not insist
463 that all other programs distributed on the same medium
464 must be free software.
465 </item>
466 <tag>10. Example Licenses
467 </tag>
468 <item>
469 The "GPL," "BSD," and "Artistic" licenses are examples of
470 licenses that we consider <em>free</em>.
471 </item>
472 </taglist>
473 </p>
474 </sect>
476 <sect id="sections">
477 <heading>Archive areas</heading>
479 <sect1 id="main">
480 <heading>The main archive area</heading>
483 The <em>main</em> archive area comprises the Debian
484 distribution. Only the packages in this area are considered
485 part of the distribution. None of the packages in
486 the <em>main</em> archive area require software outside of
487 that area to function. Anyone may use, share, modify and
488 redistribute the packages in this archive area
489 freely<footnote>
490 See <url id="http://www.debian.org/intro/free"
491 name="What Does Free Mean?"> for
492 more about what we mean by free software.
493 </footnote>.
494 </p>
497 Every package in <em>main</em> must comply with the DFSG
498 (Debian Free Software Guidelines).
499 </p>
502 In addition, the packages in <em>main</em>
503 <list compact="compact">
504 <item>
505 must not require or recommend a package outside
506 of <em>main</em> for compilation or execution (thus, the
507 package must not declare a "Pre-Depends", "Depends",
508 "Recommends", "Build-Depends", or "Build-Depends-Indep"
509 relationship on a non-<em>main</em> package),
510 </item>
511 <item>
512 must not be so buggy that we refuse to support them,
514 </item>
515 <item>
516 must meet all policy requirements presented in this
517 manual.
518 </item>
519 </list>
520 </p>
522 </sect1>
524 <sect1 id="contrib">
525 <heading>The contrib archive area</heading>
528 The <em>contrib</em> archive area contains supplemental
529 packages intended to work with the Debian distribution, but
530 which require software outside of the distribution to either
531 build or function.
532 </p>
535 Every package in <em>contrib</em> must comply with the DFSG.
536 </p>
539 In addition, the packages in <em>contrib</em>
540 <list compact="compact">
541 <item>
542 must not be so buggy that we refuse to support them,
544 </item>
545 <item>
546 must meet all policy requirements presented in this
547 manual.
548 </item>
549 </list>
550 </p>
553 Examples of packages which would be included in
554 <em>contrib</em> are:
555 <list compact="compact">
556 <item>
557 free packages which require <em>contrib</em>,
558 <em>non-free</em> packages or packages which are not
559 in our archive at all for compilation or execution,
561 </item>
562 <item>
563 wrapper packages or other sorts of free accessories for
564 non-free programs.
565 </item>
566 </list>
567 </p>
568 </sect1>
570 <sect1 id="non-free">
571 <heading>The non-free archive area</heading>
574 The <em>non-free</em> archive area contains supplemental
575 packages intended to work with the Debian distribution that do
576 not comply with the DFSG or have other problems that make
577 their distribution problematic. They may not comply with all
578 of the policy requirements in this manual due to restrictions
579 on modifications or other limitations.
580 </p>
583 Packages must be placed in <em>non-free</em> if they are
584 not compliant with the DFSG or are encumbered by patents
585 or other legal issues that make their distribution
586 problematic.
587 </p>
590 In addition, the packages in <em>non-free</em>
591 <list compact="compact">
592 <item>
593 must not be so buggy that we refuse to support them,
595 </item>
596 <item>
597 must meet all policy requirements presented in this
598 manual that it is possible for them to meet.
599 <footnote>
600 It is possible that there are policy
601 requirements which the package is unable to
602 meet, for example, if the source is
603 unavailable. These situations will need to be
604 handled on a case-by-case basis.
605 </footnote>
606 </item>
607 </list>
608 </p>
609 </sect1>
611 </sect>
613 <sect id="pkgcopyright">
614 <heading>Copyright considerations</heading>
617 Every package must be accompanied by a verbatim copy of its
618 copyright information and distribution license in the file
619 <file>/usr/share/doc/<var>package</var>/copyright</file>
620 (see <ref id="copyrightfile"> for further details).
621 </p>
624 We reserve the right to restrict files from being included
625 anywhere in our archives if
626 <list compact="compact">
627 <item>
628 their use or distribution would break a law,
629 </item>
630 <item>
631 there is an ethical conflict in their distribution or
632 use,
633 </item>
634 <item>
635 we would have to sign a license for them, or
636 </item>
637 <item>
638 their distribution would conflict with other project
639 policies.
640 </item>
641 </list>
642 </p>
645 Programs whose authors encourage the user to make
646 donations are fine for the main distribution, provided
647 that the authors do not claim that not donating is
648 immoral, unethical, illegal or something similar; in such
649 a case they must go in <em>non-free</em>.
650 </p>
653 Packages whose copyright permission notices (or patent
654 problems) do not even allow redistribution of binaries
655 only, and where no special permission has been obtained,
656 must not be placed on the Debian FTP site and its mirrors
657 at all.
658 </p>
661 Note that under international copyright law (this applies
662 in the United States, too), <em>no</em> distribution or
663 modification of a work is allowed without an explicit
664 notice saying so. Therefore a program without a copyright
665 notice <em>is</em> copyrighted and you may not do anything
666 to it without risking being sued! Likewise if a program
667 has a copyright notice but no statement saying what is
668 permitted then nothing is permitted.
669 </p>
672 Many authors are unaware of the problems that restrictive
673 copyrights (or lack of copyright notices) can cause for
674 the users of their supposedly-free software. It is often
675 worthwhile contacting such authors diplomatically to ask
676 them to modify their license terms. However, this can be a
677 politically difficult thing to do and you should ask for
678 advice on the <tt>debian-legal</tt> mailing list first, as
679 explained below.
680 </p>
683 When in doubt about a copyright, send mail to
684 <email>debian-legal@lists.debian.org</email>. Be prepared
685 to provide us with the copyright statement. Software
686 covered by the GPL, public domain software and BSD-like
687 copyrights are safe; be wary of the phrases "commercial
688 use prohibited" and "distribution restricted".
689 </p>
690 </sect>
692 <sect id="subsections">
693 <heading>Sections</heading>
696 The packages in the archive areas <em>main</em>,
697 <em>contrib</em> and <em>non-free</em> are grouped further into
698 <em>sections</em> to simplify handling.
699 </p>
702 The archive area and section for each package should be
703 specified in the package's <tt>Section</tt> control record (see
704 <ref id="f-Section">). However, the maintainer of the Debian
705 archive may override this selection to ensure the consistency of
706 the Debian distribution. The <tt>Section</tt> field should be
707 of the form:
708 <list compact="compact">
709 <item>
710 <em>section</em> if the package is in the
711 <em>main</em> archive area,
712 </item>
713 <item>
714 <em>area/section</em> if the package is in
715 the <em>contrib</em> or <em>non-free</em>
716 archive areas.
717 </item>
718 </list>
719 </p>
722 The Debian archive maintainers provide the authoritative
723 list of sections. At present, they are:
724 admin,
725 cli-mono,
726 comm,
727 database,
728 debug,
729 devel,
730 doc,
731 editors,
732 education,
733 electronics,
734 embedded,
735 fonts,
736 games,
737 gnome,
738 gnu-r,
739 gnustep,
740 graphics,
741 hamradio,
742 haskell,
743 httpd,
744 interpreters,
745 introspection,
746 java,
747 kde,
748 kernel,
749 libdevel,
750 libs,
751 lisp,
752 localization,
753 mail,
754 math,
755 metapackages,
756 misc,
757 net,
758 news,
759 ocaml,
760 oldlibs,
761 otherosfs,
762 perl,
763 php,
764 python,
765 ruby,
766 science,
767 shells,
768 sound,
769 tasks,
770 tex,
771 text,
772 utils,
773 vcs,
774 video,
775 web,
776 x11,
777 xfce,
778 zope.
779 The additional section <em>debian-installer</em>
780 contains special packages used by the installer and is not used
781 for normal Debian packages.
782 </p>
785 For more information about the sections and their definitions,
786 see the <url id="http://packages.debian.org/unstable/"
787 name="list of sections in unstable">.
788 </p>
789 </sect>
791 <sect id="priorities">
792 <heading>Priorities</heading>
795 Each package should have a <em>priority</em> value, which is
796 included in the package's <em>control record</em>
797 (see <ref id="f-Priority">).
798 This information is used by the Debian package management tools to
799 separate high-priority packages from less-important packages.
800 </p>
803 The following <em>priority levels</em> are recognized by the
804 Debian package management tools.
805 <taglist>
806 <tag><tt>required</tt></tag>
807 <item>
808 Packages which are necessary for the proper
809 functioning of the system (usually, this means that
810 dpkg functionality depends on these packages).
811 Removing a <tt>required</tt> package may cause your
812 system to become totally broken and you may not even
813 be able to use <prgn>dpkg</prgn> to put things back,
814 so only do so if you know what you are doing. Systems
815 with only the <tt>required</tt> packages are probably
816 unusable, but they do have enough functionality to
817 allow the sysadmin to boot and install more software.
818 </item>
819 <tag><tt>important</tt></tag>
820 <item>
821 Important programs, including those which one would
822 expect to find on any Unix-like system. If the
823 expectation is that an experienced Unix person who
824 found it missing would say "What on earth is going on,
825 where is <prgn>foo</prgn>?", it must be an
826 <tt>important</tt> package.<footnote>
827 This is an important criterion because we are
828 trying to produce, amongst other things, a free
829 Unix.
830 </footnote>
831 Other packages without which the system will not run
832 well or be usable must also have priority
833 <tt>important</tt>. This does
834 <em>not</em> include Emacs, the X Window System, TeX
835 or any other large applications. The
836 <tt>important</tt> packages are just a bare minimum of
837 commonly-expected and necessary tools.
838 </item>
839 <tag><tt>standard</tt></tag>
840 <item>
841 These packages provide a reasonably small but not too
842 limited character-mode system. This is what will be
843 installed by default if the user doesn't select anything
844 else. It doesn't include many large applications.
845 </item>
846 <tag><tt>optional</tt></tag>
847 <item>
848 (In a sense everything that isn't required is
849 optional, but that's not what is meant here.) This is
850 all the software that you might reasonably want to
851 install if you didn't know what it was and don't have
852 specialized requirements. This is a much larger system
853 and includes the X Window System, a full TeX
854 distribution, and many applications. Note that
855 optional packages should not conflict with each other.
856 </item>
857 <tag><tt>extra</tt></tag>
858 <item>
859 This contains all packages that conflict with others
860 with required, important, standard or optional
861 priorities, or are only likely to be useful if you
862 already know what they are or have specialized
863 requirements (such as packages containing only detached
864 debugging symbols).
865 </item>
866 </taglist>
867 </p>
870 Packages must not depend on packages with lower priority
871 values (excluding build-time dependencies). In order to
872 ensure this, the priorities of one or more packages may need
873 to be adjusted.
874 </p>
875 </sect>
877 </chapt>
880 <chapt id="binary">
881 <heading>Binary packages</heading>
884 The Debian distribution is based on the Debian
885 package management system, called <prgn>dpkg</prgn>. Thus,
886 all packages in the Debian distribution must be provided
887 in the <tt>.deb</tt> file format.
888 </p>
891 A <tt>.deb</tt> package contains two sets of files: a set of files
892 to install on the system when the package is installed, and a set
893 of files that provide additional metadata about the package or
894 which are executed when the package is installed or removed. This
895 second set of files is called <em>control information files</em>.
896 Among those files are the package maintainer scripts
897 and <file>control</file>, the <qref id="binarycontrolfiles">binary
898 package control file</qref> that contains the control fields for
899 the package. Other control information files include
900 the <qref id="sharedlibs-symbols"><file>symbols</file> file</qref>
901 or <qref id="sharedlibs-shlibdeps"><file>shlibs</file> file</qref>
902 used to store shared library dependency information and
903 the <file>conffiles</file> file that lists the package's
904 configuration files (described in <ref id="config-files">).
905 </p>
908 There is unfortunately a collision of terminology here between
909 control information files and files in the Debian control file
910 format. Throughout this document, a <em>control file</em> refers
911 to a file in the Debian control file format. These files are
912 documented in <ref id="controlfields">. Only files referred to
913 specifically as <em>control information files</em> are the files
914 included in the control information file member of
915 the <file>.deb</file> file format used by binary packages. Most
916 control information files are not in the Debian control file
917 format.
918 </p>
920 <sect>
921 <heading>The package name</heading>
924 Every package must have a name that's unique within the Debian
925 archive.
926 </p>
929 The package name is included in the control field
930 <tt>Package</tt>, the format of which is described
931 in <ref id="f-Package">.
932 The package name is also included as a part of the file name
933 of the <tt>.deb</tt> file.
934 </p>
935 </sect>
937 <sect id="versions">
938 <heading>The version of a package</heading>
941 Every package has a version number recorded in its
942 <tt>Version</tt> control file field, described in
943 <ref id="f-Version">.
944 </p>
947 The package management system imposes an ordering on version
948 numbers, so that it can tell whether packages are being up- or
949 downgraded and so that package system front end applications
950 can tell whether a package it finds available is newer than
951 the one installed on the system. The version number format
952 has the most significant parts (as far as comparison is
953 concerned) at the beginning.
954 </p>
957 If an upstream package has problematic version numbers they
958 should be converted to a sane form for use in the
959 <tt>Version</tt> field.
960 </p>
962 <sect1>
963 <heading>Version numbers based on dates</heading>
966 In general, Debian packages should use the same version
967 numbers as the upstream sources. However, upstream version
968 numbers based on some date formats (sometimes used for
969 development or "snapshot" releases) will not be ordered
970 correctly by the package management software. For
971 example, <prgn>dpkg</prgn> will consider "96May01" to be
972 greater than "96Dec24".
973 </p>
976 To prevent having to use epochs for every new upstream
977 version, the date-based portion of any upstream version number
978 should be given in a way that sorts correctly: four-digit year
979 first, followed by a two-digit numeric month, followed by a
980 two-digit numeric date, possibly with punctuation between the
981 components.
982 </p>
985 Native Debian packages (i.e., packages which have been written
986 especially for Debian) whose version numbers include dates
987 should also follow these rules. If punctuation is desired
988 between the date components, remember that hyphen (<tt>-</tt>)
989 cannot be used in native package versions. Period
990 (<tt>.</tt>) is normally a good choice.
991 </p>
992 </sect1>
994 </sect>
996 <sect id="maintainer">
997 <heading>The maintainer of a package</heading>
1000 Every package must have a maintainer, except for orphaned
1001 packages as described below. The maintainer may be one person
1002 or a group of people reachable from a common email address, such
1003 as a mailing list. The maintainer is responsible for
1004 maintaining the Debian packaging files, evaluating and
1005 responding appropriately to reported bugs, uploading new
1006 versions of the package (either directly or through a sponsor),
1007 ensuring that the package is placed in the appropriate archive
1008 area and included in Debian releases as appropriate for the
1009 stability and utility of the package, and requesting removal of
1010 the package from the Debian distribution if it is no longer
1011 useful or maintainable.
1012 </p>
1015 The maintainer must be specified in the <tt>Maintainer</tt>
1016 control field with their correct name and a working email
1017 address. The email address given in the <tt>Maintainer</tt>
1018 control field must accept mail from those role accounts in
1019 Debian used to send automated mails regarding the package. This
1020 includes non-spam mail from the bug-tracking system, all mail
1021 from the Debian archive maintenance software, and other role
1022 accounts or automated processes that are commonly agreed on by
1023 the project.<footnote>
1024 A sample implementation of such a whitelist written for the
1025 Mailman mailing list management software is used for mailing
1026 lists hosted by alioth.debian.org.
1027 </footnote>
1028 If one person or team maintains several packages, they should
1029 use the same form of their name and email address in
1030 the <tt>Maintainer</tt> fields of those packages.
1031 </p>
1034 The format of the <tt>Maintainer</tt> control field is
1035 described in <ref id="f-Maintainer">.
1036 </p>
1039 If the maintainer of the package is a team of people with a
1040 shared email address, the <tt>Uploaders</tt> control field must
1041 be present and must contain at least one human with their
1042 personal email address. See <ref id="f-Uploaders"> for the
1043 syntax of that field.
1044 </p>
1047 An orphaned package is one with no current maintainer. Orphaned
1048 packages should have their <tt>Maintainer</tt> control field set
1049 to <tt>Debian QA Group &lt;packages@qa.debian.org&gt;</tt>.
1050 These packages are considered maintained by the Debian project
1051 as a whole until someone else volunteers to take over
1052 maintenance.<footnote>
1053 The detailed procedure for gracefully orphaning a package can
1054 be found in the Debian Developer's Reference
1055 (see <ref id="related">).
1056 </footnote>
1057 </p>
1058 </sect>
1060 <sect id="descriptions">
1061 <heading>The description of a package</heading>
1064 Every Debian package must have a <tt>Description</tt> control
1065 field which contains a synopsis and extended description of the
1066 package. Technical information about the format of the
1067 <tt>Description</tt> field is in <ref id="f-Description">.
1068 </p>
1071 The description should describe the package (the program) to a
1072 user (system administrator) who has never met it before so that
1073 they have enough information to decide whether they want to
1074 install it. This description should not just be copied verbatim
1075 from the program's documentation.
1076 </p>
1079 Put important information first, both in the synopsis and
1080 extended description. Sometimes only the first part of the
1081 synopsis or of the description will be displayed. You can
1082 assume that there will usually be a way to see the whole
1083 extended description.
1084 </p>
1087 The description should also give information about the
1088 significant dependencies and conflicts between this package
1089 and others, so that the user knows why these dependencies and
1090 conflicts have been declared.
1091 </p>
1094 Instructions for configuring or using the package should
1095 not be included (that is what installation scripts,
1096 manual pages, info files, etc., are for). Copyright
1097 statements and other administrivia should not be included
1098 either (that is what the copyright file is for).
1099 </p>
1101 <sect1 id="synopsis"><heading>The single line synopsis</heading>
1104 The single line synopsis should be kept brief - certainly
1105 under 80 characters.
1106 </p>
1109 Do not include the package name in the synopsis line. The
1110 display software knows how to display this already, and you
1111 do not need to state it. Remember that in many situations
1112 the user may only see the synopsis line - make it as
1113 informative as you can.
1114 </p>
1116 </sect1>
1118 <sect1 id="extendeddesc"><heading>The extended description</heading>
1121 Do not try to continue the single line synopsis into the
1122 extended description. This will not work correctly when
1123 the full description is displayed, and makes no sense
1124 where only the summary (the single line synopsis) is
1125 available.
1126 </p>
1129 The extended description should describe what the package
1130 does and how it relates to the rest of the system (in terms
1131 of, for example, which subsystem it is which part of).
1132 </p>
1135 The description field needs to make sense to anyone, even
1136 people who have no idea about any of the things the
1137 package deals with.<footnote>
1138 The blurb that comes with a program in its
1139 announcements and/or <prgn>README</prgn> files is
1140 rarely suitable for use in a description. It is
1141 usually aimed at people who are already in the
1142 community where the package is used.
1143 </footnote>
1144 </p>
1146 </sect1>
1148 </sect>
1150 <sect id="dependencies">
1151 <heading>Dependencies</heading>
1154 Every package must specify the dependency information
1155 about other packages that are required for the first to
1156 work correctly.
1157 </p>
1160 For example, a dependency entry must be provided for any
1161 shared libraries required by a dynamically-linked executable
1162 binary in a package.
1163 </p>
1166 Packages are not required to declare any dependencies they
1167 have on other packages which are marked <tt>Essential</tt>
1168 (see below), and should not do so unless they depend on a
1169 particular version of that package.<footnote>
1171 Essential is needed in part to avoid unresolvable dependency
1172 loops on upgrade. If packages add unnecessary dependencies
1173 on packages in this set, the chances that there
1174 <strong>will</strong> be an unresolvable dependency loop
1175 caused by forcing these Essential packages to be configured
1176 first before they need to be is greatly increased. It also
1177 increases the chances that frontends will be unable to
1178 <strong>calculate</strong> an upgrade path, even if one
1179 exists.
1180 </p>
1182 Also, functionality is rarely ever removed from the
1183 Essential set, but <em>packages</em> have been removed from
1184 the Essential set when the functionality moved to a
1185 different package. So depending on these packages <em>just
1186 in case</em> they stop being essential does way more harm
1187 than good.
1188 </p>
1189 </footnote>
1190 </p>
1193 Sometimes, unpacking one package requires that another package
1194 be first unpacked <em>and</em> configured. In this case, the
1195 depending package must specify this dependency in
1196 the <tt>Pre-Depends</tt> control field.
1197 </p>
1200 You should not specify a <tt>Pre-Depends</tt> entry for a
1201 package before this has been discussed on the
1202 <tt>debian-devel</tt> mailing list and a consensus about
1203 doing that has been reached.
1204 </p>
1207 The format of the package interrelationship control fields is
1208 described in <ref id="relationships">.
1209 </p>
1210 </sect>
1212 <sect id="virtual_pkg">
1213 <heading>Virtual packages</heading>
1216 Sometimes, there are several packages which offer
1217 more-or-less the same functionality. In this case, it's
1218 useful to define a <em>virtual package</em> whose name
1219 describes that common functionality. (The virtual
1220 packages only exist logically, not physically; that's why
1221 they are called <em>virtual</em>.) The packages with this
1222 particular function will then <em>provide</em> the virtual
1223 package. Thus, any other package requiring that function
1224 can simply depend on the virtual package without having to
1225 specify all possible packages individually.
1226 </p>
1229 All packages should use virtual package names where
1230 appropriate, and arrange to create new ones if necessary.
1231 They should not use virtual package names (except privately,
1232 amongst a cooperating group of packages) unless they have
1233 been agreed upon and appear in the list of virtual package
1234 names. (See also <ref id="virtual">)
1235 </p>
1238 The latest version of the authoritative list of virtual
1239 package names can be found in the <tt>debian-policy</tt> package.
1240 It is also available from the Debian web mirrors at
1241 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1242 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1243 </p>
1246 The procedure for updating the list is described in the preface
1247 to the list.
1248 </p>
1250 </sect>
1252 <sect>
1253 <heading>Base system</heading>
1256 The <tt>base system</tt> is a minimum subset of the Debian
1257 system that is installed before everything else
1258 on a new system. Only very few packages are allowed to form
1259 part of the base system, in order to keep the required disk
1260 usage very small.
1261 </p>
1264 The base system consists of all those packages with priority
1265 <tt>required</tt> or <tt>important</tt>. Many of them will
1266 be tagged <tt>essential</tt> (see below).
1267 </p>
1268 </sect>
1270 <sect>
1271 <heading>Essential packages</heading>
1274 Essential is defined as the minimal set of functionality that
1275 must be available and usable on the system at all times, even
1276 when packages are in the "Unpacked" state.
1277 Packages are tagged <tt>essential</tt> for a system using the
1278 <tt>Essential</tt> control field. The format of the
1279 <tt>Essential</tt> control field is described in <ref
1280 id="f-Essential">.
1281 </p>
1284 Since these packages cannot be easily removed (one has to
1285 specify an extra <em>force option</em> to
1286 <prgn>dpkg</prgn> to do so), this flag must not be used
1287 unless absolutely necessary. A shared library package
1288 must not be tagged <tt>essential</tt>; dependencies will
1289 prevent its premature removal, and we need to be able to
1290 remove it when it has been superseded.
1291 </p>
1294 Since dpkg will not prevent upgrading of other packages
1295 while an <tt>essential</tt> package is in an unconfigured
1296 state, all <tt>essential</tt> packages must supply all of
1297 their core functionality even when unconfigured. If the
1298 package cannot satisfy this requirement it must not be
1299 tagged as essential, and any packages depending on this
1300 package must instead have explicit dependency fields as
1301 appropriate.
1302 </p>
1305 Maintainers should take great care in adding any programs,
1306 interfaces, or functionality to <tt>essential</tt> packages.
1307 Packages may assume that functionality provided by
1308 <tt>essential</tt> packages is always available without
1309 declaring explicit dependencies, which means that removing
1310 functionality from the Essential set is very difficult and is
1311 almost never done. Any capability added to an
1312 <tt>essential</tt> package therefore creates an obligation to
1313 support that capability as part of the Essential set in
1314 perpetuity.
1315 </p>
1318 You must not tag any packages <tt>essential</tt> before
1319 this has been discussed on the <tt>debian-devel</tt>
1320 mailing list and a consensus about doing that has been
1321 reached.
1322 </p>
1323 </sect>
1325 <sect id="maintscripts">
1326 <heading>Maintainer Scripts</heading>
1329 The package installation scripts should avoid producing
1330 output which is unnecessary for the user to see and
1331 should rely on <prgn>dpkg</prgn> to stave off boredom on
1332 the part of a user installing many packages. This means,
1333 amongst other things, not passing the <tt>--verbose</tt>
1334 option to <prgn>update-alternatives</prgn>.
1335 </p>
1338 Errors which occur during the execution of an installation
1339 script must be checked and the installation must not
1340 continue after an error.
1341 </p>
1344 Note that in general <ref id="scripts"> applies to package
1345 maintainer scripts, too.
1346 </p>
1349 You should not use <prgn>dpkg-divert</prgn> on a file belonging
1350 to another package without consulting the maintainer of that
1351 package first. When adding or removing diversions, package
1352 maintainer scripts must provide the <tt>--package</tt> flag
1353 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1354 </p>
1357 All packages which supply an instance of a common command
1358 name (or, in general, filename) should generally use
1359 <prgn>update-alternatives</prgn>, so that they may be
1360 installed together. If <prgn>update-alternatives</prgn>
1361 is not used, then each package must use
1362 <tt>Conflicts</tt> to ensure that other packages are
1363 removed. (In this case, it may be appropriate to
1364 specify a conflict against earlier versions of something
1365 that previously did not use
1366 <prgn>update-alternatives</prgn>; this is an exception to
1367 the usual rule that versioned conflicts should be
1368 avoided.)
1369 </p>
1371 <sect1 id="maintscriptprompt">
1372 <heading>Prompting in maintainer scripts</heading>
1374 Package maintainer scripts may prompt the user if
1375 necessary. Prompting must be done by communicating
1376 through a program, such as <prgn>debconf</prgn>, which
1377 conforms to the Debian Configuration Management
1378 Specification, version 2 or higher.
1379 </p>
1382 Packages which are essential, or which are dependencies of
1383 essential packages, may fall back on another prompting method
1384 if no such interface is available when they are executed.
1385 </p>
1388 The Debian Configuration Management Specification is included
1389 in the <file>debconf_specification</file> files in the
1390 <package>debian-policy</package> package.
1391 It is also available from the Debian web mirrors at
1392 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1393 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1394 </p>
1397 Packages which use the Debian Configuration Management
1398 Specification may contain the additional control information
1399 files <file>config</file>
1400 and <file>templates</file>. <file>config</file> is an
1401 additional maintainer script used for package configuration,
1402 and <file>templates</file> contains templates used for user
1403 prompting. The <prgn>config</prgn> script might be run before
1404 the <prgn>preinst</prgn> script and before the package is
1405 unpacked or any of its dependencies or pre-dependencies are
1406 satisfied. Therefore it must work using only the tools
1407 present in <em>essential</em> packages.<footnote>
1408 <package>Debconf</package> or another tool that
1409 implements the Debian Configuration Management
1410 Specification will also be installed, and any
1411 versioned dependencies on it will be satisfied
1412 before preconfiguration begins.
1413 </footnote>
1414 </p>
1417 Packages which use the Debian Configuration Management
1418 Specification must allow for translation of their user-visible
1419 messages by using a gettext-based system such as the one
1420 provided by the <package>po-debconf</package> package.
1421 </p>
1424 Packages should try to minimize the amount of prompting
1425 they need to do, and they should ensure that the user
1426 will only ever be asked each question once. This means
1427 that packages should try to use appropriate shared
1428 configuration files (such as <file>/etc/papersize</file> and
1429 <file>/etc/news/server</file>), and shared
1430 <package>debconf</package> variables rather than each
1431 prompting for their own list of required pieces of
1432 information.
1433 </p>
1436 It also means that an upgrade should not ask the same
1437 questions again, unless the user has used
1438 <tt>dpkg --purge</tt> to remove the package's configuration.
1439 The answers to configuration questions should be stored in an
1440 appropriate place in <file>/etc</file> so that the user can
1441 modify them, and how this has been done should be
1442 documented.
1443 </p>
1446 If a package has a vitally important piece of
1447 information to pass to the user (such as "don't run me
1448 as I am, you must edit the following configuration files
1449 first or you risk your system emitting badly-formatted
1450 messages"), it should display this in the
1451 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1452 prompt the user to hit return to acknowledge the
1453 message. Copyright messages do not count as vitally
1454 important (they belong in
1455 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1456 neither do instructions on how to use a program (these
1457 should be in on-line documentation, where all the users
1458 can see them).
1459 </p>
1462 Any necessary prompting should almost always be confined
1463 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1464 script. If it is done in the <prgn>postinst</prgn>, it
1465 should be protected with a conditional so that
1466 unnecessary prompting doesn't happen if a package's
1467 installation fails and the <prgn>postinst</prgn> is
1468 called with <tt>abort-upgrade</tt>,
1469 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1470 </p>
1471 </sect1>
1473 </sect>
1475 </chapt>
1478 <chapt id="source">
1479 <heading>Source packages</heading>
1481 <sect id="standardsversion">
1482 <heading>Standards conformance</heading>
1485 Source packages should specify the most recent version number
1486 of this policy document with which your package complied
1487 when it was last updated.
1488 </p>
1491 This information may be used to file bug reports
1492 automatically if your package becomes too much out of date.
1493 </p>
1496 The version is specified in the <tt>Standards-Version</tt>
1497 control field.
1498 The format of the <tt>Standards-Version</tt> field is
1499 described in <ref id="f-Standards-Version">.
1500 </p>
1503 You should regularly, and especially if your package has
1504 become out of date, check for the newest Policy Manual
1505 available and update your package, if necessary. When your
1506 package complies with the new standards you should update the
1507 <tt>Standards-Version</tt> source package field and
1508 release it.<footnote>
1509 See the file <file>upgrading-checklist</file> for
1510 information about policy which has changed between
1511 different versions of this document.
1512 </footnote>
1513 </p>
1515 </sect>
1517 <sect id="pkg-relations">
1518 <heading>Package relationships</heading>
1521 Source packages should specify which binary packages they
1522 require to be installed or not to be installed in order to
1523 build correctly. For example, if building a package
1524 requires a certain compiler, then the compiler should be
1525 specified as a build-time dependency.
1526 </p>
1529 It is not necessary to explicitly specify build-time
1530 relationships on a minimal set of packages that are always
1531 needed to compile, link and put in a Debian package a
1532 standard "Hello World!" program written in C or C++. The
1533 required packages are called <em>build-essential</em>, and
1534 an informational list can be found in
1535 <file>/usr/share/doc/build-essential/list</file> (which is
1536 contained in the <tt>build-essential</tt>
1537 package).<footnote>
1538 Rationale:
1539 <list compact="compact">
1540 <item>
1541 This allows maintaining the list separately
1542 from the policy documents (the list does not
1543 need the kind of control that the policy
1544 documents do).
1545 </item>
1546 <item>
1547 Having a separate package allows one to install
1548 the build-essential packages on a machine, as
1549 well as allowing other packages such as tasks to
1550 require installation of the build-essential
1551 packages using the depends relation.
1552 </item>
1553 <item>
1554 The separate package allows bug reports against
1555 the list to be categorized separately from
1556 the policy management process in the BTS.
1557 </item>
1558 </list>
1559 </footnote>
1560 </p>
1563 When specifying the set of build-time dependencies, one
1564 should list only those packages explicitly required by the
1565 build. It is not necessary to list packages which are
1566 required merely because some other package in the list of
1567 build-time dependencies depends on them.<footnote>
1568 The reason for this is that dependencies change, and
1569 you should list all those packages, and <em>only</em>
1570 those packages that <em>you</em> need directly. What
1571 others need is their business. For example, if you
1572 only link against <file>libimlib</file>, you will need to
1573 build-depend on <package>libimlib2-dev</package> but
1574 not against any <tt>libjpeg*</tt> packages, even
1575 though <tt>libimlib2-dev</tt> currently depends on
1576 them: installation of <package>libimlib2-dev</package>
1577 will automatically ensure that all of its run-time
1578 dependencies are satisfied.
1579 </footnote>
1580 </p>
1583 If build-time dependencies are specified, it must be
1584 possible to build the package and produce working binaries
1585 on a system with only essential and build-essential
1586 packages installed and also those required to satisfy the
1587 build-time relationships (including any implied
1588 relationships). In particular, this means that version
1589 clauses should be used rigorously in build-time
1590 relationships so that one cannot produce bad or
1591 inconsistently configured packages when the relationships
1592 are properly satisfied.
1593 </p>
1596 <ref id="relationships"> explains the technical details.
1597 </p>
1598 </sect>
1600 <sect>
1601 <heading>Changes to the upstream sources</heading>
1604 If changes to the source code are made that are not
1605 specific to the needs of the Debian system, they should be
1606 sent to the upstream authors in whatever form they prefer
1607 so as to be included in the upstream version of the
1608 package.
1609 </p>
1612 If you need to configure the package differently for
1613 Debian or for Linux, and the upstream source doesn't
1614 provide a way to do so, you should add such configuration
1615 facilities (for example, a new <prgn>autoconf</prgn> test
1616 or <tt>#define</tt>) and send the patch to the upstream
1617 authors, with the default set to the way they originally
1618 had it. You can then easily override the default in your
1619 <file>debian/rules</file> or wherever is appropriate.
1620 </p>
1623 You should make sure that the <prgn>configure</prgn> utility
1624 detects the correct architecture specification string
1625 (refer to <ref id="arch-spec"> for details).
1626 </p>
1629 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1630 <prgn>configure</prgn> scripts are used, you should edit the
1631 <file>.in</file> files rather than editing the
1632 <prgn>Makefile</prgn> directly. This allows the user to
1633 reconfigure the package if necessary. You should
1634 <em>not</em> configure the package and edit the generated
1635 <prgn>Makefile</prgn>! This makes it impossible for someone
1636 else to later reconfigure the package without losing the
1637 changes you made.
1638 </p>
1640 </sect>
1642 <sect id="dpkgchangelog">
1643 <heading>Debian changelog: <file>debian/changelog</file></heading>
1646 Changes in the Debian version of the package should be
1647 briefly explained in the Debian changelog file
1648 <file>debian/changelog</file>.<footnote>
1650 Mistakes in changelogs are usually best rectified by
1651 making a new changelog entry rather than "rewriting
1652 history" by editing old changelog entries.
1653 </p>
1654 </footnote>
1655 This includes modifications
1656 made in the Debian package compared to the upstream one
1657 as well as other changes and updates to the package.
1658 <footnote>
1659 Although there is nothing stopping an author who is also
1660 the Debian maintainer from using this changelog for all
1661 their changes, it will have to be renamed if the Debian
1662 and upstream maintainers become different people. In such
1663 a case, however, it might be better to maintain the package
1664 as a non-native package.
1665 </footnote>
1666 </p>
1669 The format of the <file>debian/changelog</file> allows the
1670 package building tools to discover which version of the package
1671 is being built and find out other release-specific information.
1672 </p>
1675 That format is a series of entries like this:
1677 <example compact="compact">
1678 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1679 <var>
1680 [optional blank line(s), stripped]
1681 </var>
1682 * <var>change details</var>
1683 <var>more change details</var>
1684 <var>
1685 [blank line(s), included in output of dpkg-parsechangelog]
1686 </var>
1687 * <var>even more change details</var>
1688 <var>
1689 [optional blank line(s), stripped]
1690 </var>
1691 -- <var>maintainer name</var> &lt;<var>email address</var>&gt;<var>[two spaces]</var> <var>date</var>
1692 </example>
1693 </p>
1696 <var>package</var> and <var>version</var> are the source
1697 package name and version number.
1698 </p>
1701 <var>distribution(s)</var> lists the distributions where
1702 this version should be installed when it is uploaded - it
1703 is copied to the <tt>Distribution</tt> field in the
1704 <file>.changes</file> file. See <ref id="f-Distribution">.
1705 </p>
1708 <var>urgency</var> is the value for the <tt>Urgency</tt>
1709 field in the <file>.changes</file> file for the upload
1710 (see <ref id="f-Urgency">). It is not possible to specify
1711 an urgency containing commas; commas are used to separate
1712 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1713 <prgn>dpkg</prgn> changelog format (though there is
1714 currently only one useful <var>keyword</var>,
1715 <tt>urgency</tt>).
1716 </p>
1719 The change details may in fact be any series of lines
1720 starting with at least two spaces, but conventionally each
1721 change starts with an asterisk and a separating space and
1722 continuation lines are indented so as to bring them in
1723 line with the start of the text above. Blank lines may be
1724 used here to separate groups of changes, if desired.
1725 </p>
1728 If this upload resolves bugs recorded in the Bug Tracking
1729 System (BTS), they may be automatically closed on the
1730 inclusion of this package into the Debian archive by
1731 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1732 in the change details.<footnote>
1733 To be precise, the string should match the following
1734 Perl regular expression:
1735 <example>
1736 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1737 </example>
1738 Then all of the bug numbers listed will be closed by the
1739 archive maintenance software (<prgn>dak</prgn>) using the
1740 <var>version</var> of the changelog entry.
1741 </footnote>
1742 This information is conveyed via the <tt>Closes</tt> field
1743 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1744 </p>
1747 The maintainer name and email address used in the changelog
1748 should be the details of the person who prepared this release of
1749 the package. They are <em>not</em> necessarily those of the
1750 uploader or usual package maintainer.<footnote>
1751 In the case of a sponsored upload, the uploader signs the
1752 files, but the changelog maintainer name and address are those
1753 of the person who prepared this release. If the preparer of
1754 the release is not one of the usual maintainers of the package
1755 (as listed in
1756 the <qref id="f-Maintainer"><tt>Maintainer</tt></qref>
1757 or <qref id="f-Uploaders"><tt>Uploaders</tt></qref> control
1758 fields of the package), the first line of the changelog is
1759 conventionally used to explain why a non-maintainer is
1760 uploading the package. The Debian Developer's Reference
1761 (see <ref id="related">) documents the conventions
1762 used.</footnote>
1763 The information here will be copied to the <tt>Changed-By</tt>
1764 field in the <tt>.changes</tt> file
1765 (see <ref id="f-Changed-By">), and then later used to send an
1766 acknowledgement when the upload has been installed.
1767 </p>
1770 The <var>date</var> has the following format<footnote>
1771 This is the same as the format generated by <tt>date
1772 -R</tt>.
1773 </footnote> (compatible and with the same semantics of
1774 RFC 2822 and RFC 5322):
1775 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1776 where:
1777 <list compact="compact">
1778 <item>
1779 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1780 </item>
1781 <item>
1782 dd is a one- or two-digit day of the month (01-31)
1783 </item>
1784 <item>
1785 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1786 Sep, Oct, Nov, Dec
1787 </item>
1788 <item>yyyy is the four-digit year (e.g. 2010)</item>
1789 <item>hh is the two-digit hour (00-23)</item>
1790 <item>mm is the two-digit minutes (00-59)</item>
1791 <item>ss is the two-digit seconds (00-60)</item>
1792 <item>
1793 +zzzz or -zzzz is the the time zone offset from Coordinated
1794 Universal Time (UTC). "+" indicates that the time is ahead
1795 of (i.e., east of) UTC and "-" indicates that the time is
1796 behind (i.e., west of) UTC. The first two digits indicate
1797 the hour difference from UTC and the last two digits
1798 indicate the number of additional minutes difference from
1799 UTC. The last two digits must be in the range 00-59.
1800 </item>
1801 </list>
1802 </p>
1805 The first "title" line with the package name must start
1806 at the left hand margin. The "trailer" line with the
1807 maintainer and date details must be preceded by exactly
1808 one space. The maintainer details and the date must be
1809 separated by exactly two spaces.
1810 </p>
1813 The entire changelog must be encoded in UTF-8.
1814 </p>
1817 For more information on placement of the changelog files
1818 within binary packages, please see <ref id="changelogs">.
1819 </p>
1820 </sect>
1822 <sect id="dpkgcopyright">
1823 <heading>Copyright: <file>debian/copyright</file></heading>
1825 Every package must be accompanied by a verbatim copy of its
1826 copyright information and distribution license in the file
1827 <file>/usr/share/doc/<var>package</var>/copyright</file>
1828 (see <ref id="copyrightfile"> for further details). Also see
1829 <ref id="pkgcopyright"> for further considerations related
1830 to copyrights for packages.
1831 </p>
1832 </sect>
1833 <sect>
1834 <heading>Error trapping in makefiles</heading>
1837 When <prgn>make</prgn> invokes a command in a makefile
1838 (including your package's upstream makefiles and
1839 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1840 means that <prgn>sh</prgn>'s usual bad error handling
1841 properties apply: if you include a miniature script as one
1842 of the commands in your makefile you'll find that if you
1843 don't do anything about it then errors are not detected
1844 and <prgn>make</prgn> will blithely continue after
1845 problems.
1846 </p>
1849 Every time you put more than one shell command (this
1850 includes using a loop) in a makefile command you
1851 must make sure that errors are trapped. For
1852 simple compound commands, such as changing directory and
1853 then running a program, using <tt>&amp;&amp;</tt> rather
1854 than semicolon as a command separator is sufficient. For
1855 more complex commands including most loops and
1856 conditionals you should include a separate <tt>set -e</tt>
1857 command at the start of every makefile command that's
1858 actually one of these miniature shell scripts.
1859 </p>
1860 </sect>
1862 <sect id="timestamps">
1863 <heading>Time Stamps</heading>
1865 Maintainers should preserve the modification times of the
1866 upstream source files in a package, as far as is reasonably
1867 possible.<footnote>
1868 The rationale is that there is some information conveyed
1869 by knowing the age of the file, for example, you could
1870 recognize that some documentation is very old by looking
1871 at the modification time, so it would be nice if the
1872 modification time of the upstream source would be
1873 preserved.
1874 </footnote>
1875 </p>
1876 </sect>
1878 <sect id="restrictions">
1879 <heading>Restrictions on objects in source packages</heading>
1882 The source package may not contain any hard links<footnote>
1884 This is not currently detected when building source
1885 packages, but only when extracting
1886 them.
1887 </p>
1889 Hard links may be permitted at some point in the
1890 future, but would require a fair amount of
1891 work.
1892 </p>
1893 </footnote>, device special files, sockets or setuid or
1894 setgid files.<footnote>
1895 Setgid directories are allowed.
1896 </footnote>
1897 </p>
1898 </sect>
1900 <sect id="debianrules">
1901 <heading>Main building script: <file>debian/rules</file></heading>
1904 This file must be an executable makefile, and contains the
1905 package-specific recipes for compiling the package and
1906 building binary package(s) from the source.
1907 </p>
1910 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1911 so that it can be invoked by saying its name rather than
1912 invoking <prgn>make</prgn> explicitly. That is, invoking
1913 either of <tt>make -f debian/rules <em>args...</em></tt>
1914 or <tt>./debian/rules <em>args...</em></tt> must result in
1915 identical behavior.
1916 </p>
1919 The following targets are required and must be implemented
1920 by <file>debian/rules</file>: <tt>clean</tt>, <tt>binary</tt>,
1921 <tt>binary-arch</tt>, <tt>binary-indep</tt>, <tt>build</tt>,
1922 <tt>build-arch</tt> and <tt>build-indep</tt>.
1923 These are the targets called by <prgn>dpkg-buildpackage</prgn>.
1924 </p>
1927 Since an interactive <file>debian/rules</file> script makes it
1928 impossible to auto-compile that package and also makes it hard
1929 for other people to reproduce the same binary package, all
1930 required targets must be non-interactive. It also follows that
1931 any target that these targets depend on must also be
1932 non-interactive.
1933 </p>
1935 For packages in the main archive, no required targets
1936 may attempt network access.
1937 </p>
1940 The targets are as follows:
1941 <taglist>
1942 <tag><tt>build</tt> (required)</tag>
1943 <item>
1945 The <tt>build</tt> target should perform all the
1946 configuration and compilation of the package.
1947 If a package has an interactive pre-build
1948 configuration routine, the Debian source package
1949 must either be built after this has taken place (so
1950 that the binary package can be built without rerunning
1951 the configuration) or the configuration routine
1952 modified to become non-interactive. (The latter is
1953 preferable if there are architecture-specific features
1954 detected by the configuration routine.)
1955 </p>
1958 For some packages, notably ones where the same
1959 source tree is compiled in different ways to produce
1960 two binary packages, the <tt>build</tt> target
1961 does not make much sense. For these packages it is
1962 good enough to provide two (or more) targets
1963 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1964 for each of the ways of building the package, and a
1965 <tt>build</tt> target that does nothing. The
1966 <tt>binary</tt> target will have to build the
1967 package in each of the possible ways and make the
1968 binary package out of each.
1969 </p>
1972 The <tt>build</tt> target must not do anything
1973 that might require root privilege.
1974 </p>
1977 The <tt>build</tt> target may need to run the
1978 <tt>clean</tt> target first - see below.
1979 </p>
1982 When a package has a configuration and build routine
1983 which takes a long time, or when the makefiles are
1984 poorly designed, or when <tt>build</tt> needs to
1985 run <tt>clean</tt> first, it is a good idea to
1986 <tt>touch build</tt> when the build process is
1987 complete. This will ensure that if <tt>debian/rules
1988 build</tt> is run again it will not rebuild the whole
1989 program.<footnote>
1990 Another common way to do this is for <tt>build</tt>
1991 to depend on <prgn>build-stamp</prgn> and to do
1992 nothing else, and for the <prgn>build-stamp</prgn>
1993 target to do the building and to <tt>touch
1994 build-stamp</tt> on completion. This is
1995 especially useful if the build routine creates a
1996 file or directory called <tt>build</tt>; in such a
1997 case, <tt>build</tt> will need to be listed as
1998 a phony target (i.e., as a dependency of the
1999 <tt>.PHONY</tt> target). See the documentation of
2000 <prgn>make</prgn> for more information on phony
2001 targets.
2002 </footnote>
2003 </p>
2004 </item>
2006 <tag><tt>build-arch</tt> (required),
2007 <tt>build-indep</tt> (required)
2008 </tag>
2009 <item>
2011 The <tt>build-arch</tt> target must
2012 perform all the configuration and compilation required for
2013 producing all architecture-dependant binary packages
2014 (those packages for which the body of the
2015 <tt>Architecture</tt> field in <tt>debian/control</tt> is
2016 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
2017 target must perform all the configuration
2018 and compilation required for producing all
2019 architecture-independent binary packages (those packages
2020 for which the body of the <tt>Architecture</tt> field
2021 in <tt>debian/control</tt> is <tt>all</tt>).
2022 The <tt>build</tt> target
2023 should either depend on those targets or take the same
2024 actions as invoking those targets would perform.<footnote>
2025 This split allows binary-only builds to not install the
2026 dependencies required for the <tt>build-indep</tt>
2027 target and skip any resource-intensive build tasks that
2028 are only required when building architecture-independent
2029 binary packages.
2030 </footnote>
2031 </p>
2034 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
2035 must not do anything that might require root privilege.
2036 </p>
2037 </item>
2039 <tag><tt>binary</tt> (required), <tt>binary-arch</tt>
2040 (required), <tt>binary-indep</tt> (required)
2041 </tag>
2042 <item>
2044 The <tt>binary</tt> target must be all that is
2045 necessary for the user to build the binary package(s)
2046 produced from this source package. It is
2047 split into two parts: <prgn>binary-arch</prgn> builds
2048 the binary packages which are specific to a particular
2049 architecture, and <tt>binary-indep</tt> builds
2050 those which are not.
2051 </p>
2053 <tt>binary</tt> may be (and commonly is) a target with
2054 no commands which simply depends on
2055 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
2056 </p>
2058 Both <tt>binary-*</tt> targets should depend on the
2059 <tt>build</tt> target, or on the appropriate
2060 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
2061 provided, so that the package is built if it has not
2062 been already. It should then create the relevant
2063 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
2064 make their control files and <prgn>dpkg-deb</prgn> to
2065 build them and place them in the parent of the top
2066 level directory.
2067 </p>
2070 Both the <tt>binary-arch</tt> and
2071 <tt>binary-indep</tt> targets <em>must</em> exist.
2072 If one of them has nothing to do (which will always be
2073 the case if the source generates only a single binary
2074 package, whether architecture-dependent or not), it
2075 must still exist and must always succeed.
2076 </p>
2079 The <tt>binary</tt> targets must be invoked as
2080 root.<footnote>
2081 The <prgn>fakeroot</prgn> package often allows one
2082 to build a package correctly even without being
2083 root.
2084 </footnote>
2085 </p>
2086 </item>
2088 <tag><tt>clean</tt> (required)</tag>
2089 <item>
2091 This must undo any effects that the <tt>build</tt>
2092 and <tt>binary</tt> targets may have had, except
2093 that it should leave alone any output files created in
2094 the parent directory by a run of a <tt>binary</tt>
2095 target.
2096 </p>
2099 If a <tt>build</tt> file is touched at the end of
2100 the <tt>build</tt> target, as suggested above, it
2101 should be removed as the first action that
2102 <tt>clean</tt> performs, so that running
2103 <tt>build</tt> again after an interrupted
2104 <tt>clean</tt> doesn't think that everything is
2105 already done.
2106 </p>
2109 The <tt>clean</tt> target may need to be
2110 invoked as root if <tt>binary</tt> has been
2111 invoked since the last <tt>clean</tt>, or if
2112 <tt>build</tt> has been invoked as root (since
2113 <tt>build</tt> may create directories, for
2114 example).
2115 </p>
2116 </item>
2118 <tag><tt>get-orig-source</tt> (optional)</tag>
2119 <item>
2121 This target fetches the most recent version of the
2122 original source package from a canonical archive site
2123 (via FTP or WWW, for example), does any necessary
2124 rearrangement to turn it into the original source
2125 tar file format described below, and leaves it in the
2126 current directory.
2127 </p>
2130 This target may be invoked in any directory, and
2131 should take care to clean up any temporary files it
2132 may have left.
2133 </p>
2136 This target is optional, but providing it if
2137 possible is a good idea.
2138 </p>
2139 </item>
2141 <tag><tt>patch</tt> (optional)</tag>
2142 <item>
2144 This target performs whatever additional actions are
2145 required to make the source ready for editing (unpacking
2146 additional upstream archives, applying patches, etc.).
2147 It is recommended to be implemented for any package where
2148 <tt>dpkg-source -x</tt> does not result in source ready
2149 for additional modification. See
2150 <ref id="readmesource">.
2151 </p>
2152 </item>
2153 </taglist>
2156 The <tt>build</tt>, <tt>binary</tt> and
2157 <tt>clean</tt> targets must be invoked with the current
2158 directory being the package's top-level directory.
2159 </p>
2163 Additional targets may exist in <file>debian/rules</file>,
2164 either as published or undocumented interfaces or for the
2165 package's internal use.
2166 </p>
2169 The architectures we build on and build for are determined
2170 by <prgn>make</prgn> variables using the
2171 utility <prgn>dpkg-architecture</prgn>.
2172 You can determine the Debian architecture and the GNU style
2173 architecture specification string for the build architecture as
2174 well as for the host architecture. The build architecture is
2175 the architecture on which <file>debian/rules</file> is run and
2176 the package build is performed. The host architecture is the
2177 architecture on which the resulting package will be installed
2178 and run. These are normally the same, but may be different in
2179 the case of cross-compilation (building packages for one
2180 architecture on machines of a different architecture).
2181 </p>
2184 Here is a list of supported <prgn>make</prgn> variables:
2185 <list compact="compact">
2186 <item>
2187 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2188 </item>
2189 <item>
2190 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2191 </item>
2192 <item>
2193 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2194 </item>
2195 <item>
2196 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2197 specification string)
2198 </item>
2199 <item>
2200 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2201 <tt>DEB_*_GNU_TYPE</tt>)
2202 </item>
2203 <item>
2204 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2205 <tt>DEB_*_GNU_TYPE</tt>)
2206 </list>
2207 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2208 the build architecture or <tt>HOST</tt> for specification of the
2209 host architecture.
2210 </p>
2213 Backward compatibility can be provided in the rules file
2214 by setting the needed variables to suitable default
2215 values; please refer to the documentation of
2216 <prgn>dpkg-architecture</prgn> for details.
2217 </p>
2220 It is important to understand that the <tt>DEB_*_ARCH</tt>
2221 string only determines which Debian architecture we are
2222 building on or for. It should not be used to get the CPU
2223 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2224 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2225 GNU style variables should generally only be used with upstream
2226 build systems.
2227 </p>
2229 <sect1 id="debianrules-options">
2230 <heading><file>debian/rules</file> and
2231 <tt>DEB_BUILD_OPTIONS</tt></heading>
2234 Supporting the standardized environment variable
2235 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2236 contain several flags to change how a package is compiled and
2237 built. Each flag must be in the form <var>flag</var> or
2238 <var>flag</var>=<var>options</var>. If multiple flags are
2239 given, they must be separated by whitespace.<footnote>
2240 Some packages support any delimiter, but whitespace is the
2241 easiest to parse inside a makefile and avoids ambiguity with
2242 flag values that contain commas.
2243 </footnote>
2244 <var>flag</var> must start with a lowercase letter
2245 (<tt>a-z</tt>) and consist only of lowercase letters,
2246 numbers (<tt>0-9</tt>), and the characters
2247 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2248 <var>options</var> must not contain whitespace. The same
2249 tag should not be given multiple times with conflicting
2250 values. Package maintainers may assume that
2251 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2252 </p>
2255 The meaning of the following tags has been standardized:
2256 <taglist>
2257 <tag>nocheck</tag>
2258 <item>
2259 This tag says to not run any build-time test suite
2260 provided by the package.
2261 </item>
2262 <tag>noopt</tag>
2263 <item>
2264 The presence of this tag means that the package should
2265 be compiled with a minimum of optimization. For C
2266 programs, it is best to add <tt>-O0</tt> to
2267 <tt>CFLAGS</tt> (although this is usually the default).
2268 Some programs might fail to build or run at this level
2269 of optimization; it may be necessary to use
2270 <tt>-O1</tt>, for example.
2271 </item>
2272 <tag>nostrip</tag>
2273 <item>
2274 This tag means that the debugging symbols should not be
2275 stripped from the binary during installation, so that
2276 debugging information may be included in the package.
2277 </item>
2278 <tag>parallel=n</tag>
2279 <item>
2280 This tag means that the package should be built using up
2281 to <tt>n</tt> parallel processes if the package build
2282 system supports this.<footnote>
2283 Packages built with <tt>make</tt> can often implement
2284 this by passing the <tt>-j</tt><var>n</var> option to
2285 <tt>make</tt>.
2286 </footnote>
2287 If the package build system does not support parallel
2288 builds, this string must be ignored. If the package
2289 build system only supports a lower level of concurrency
2290 than <var>n</var>, the package should be built using as
2291 many parallel processes as the package build system
2292 supports. It is up to the package maintainer to decide
2293 whether the package build times are long enough and the
2294 package build system is robust enough to make supporting
2295 parallel builds worthwhile.
2296 </item>
2297 </taglist>
2298 </p>
2301 Unknown flags must be ignored by <file>debian/rules</file>.
2302 </p>
2305 The following makefile snippet is an example of how one may
2306 implement the build options; you will probably have to
2307 massage this example in order to make it work for your
2308 package.
2309 <example compact="compact">
2310 CFLAGS = -Wall -g
2311 INSTALL = install
2312 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2313 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2314 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2315 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2317 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2318 CFLAGS += -O0
2319 else
2320 CFLAGS += -O2
2321 endif
2322 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2323 INSTALL_PROGRAM += -s
2324 endif
2325 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2326 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2327 MAKEFLAGS += -j$(NUMJOBS)
2328 endif
2330 build:
2331 # ...
2332 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2333 # Code to run the package test suite.
2334 endif
2335 </example>
2336 </p>
2337 </sect1>
2338 </sect>
2340 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2341 <sect id="substvars">
2342 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2345 When <prgn>dpkg-gencontrol</prgn>
2346 generates <qref id="binarycontrolfiles">binary package control
2347 files</qref> (<file>DEBIAN/control</file>), it performs variable
2348 substitutions on its output just before writing it. Variable
2349 substitutions have the form <tt>${<var>variable</var>}</tt>.
2350 The optional file <file>debian/substvars</file> contains
2351 variable substitutions to be used; variables can also be set
2352 directly from <file>debian/rules</file> using the <tt>-V</tt>
2353 option to the source packaging commands, and certain predefined
2354 variables are also available.
2355 </p>
2358 The <file>debian/substvars</file> file is usually generated and
2359 modified dynamically by <file>debian/rules</file> targets, in
2360 which case it must be removed by the <tt>clean</tt> target.
2361 </p>
2364 See <manref name="deb-substvars" section="5"> for full
2365 details about source variable substitutions, including the
2366 format of <file>debian/substvars</file>.</p>
2367 </sect>
2369 <sect id="debianwatch">
2370 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2373 This is an optional, recommended configuration file for the
2374 <tt>uscan</tt> utility which defines how to automatically scan
2375 ftp or http sites for newly available updates of the
2376 package. This is used Debian QA
2377 tools to help with quality control and maintenance of the
2378 distribution as a whole.
2379 </p>
2381 </sect>
2383 <sect id="debianfiles">
2384 <heading>Generated files list: <file>debian/files</file></heading>
2387 This file is not a permanent part of the source tree; it
2388 is used while building packages to record which files are
2389 being generated. <prgn>dpkg-genchanges</prgn> uses it
2390 when it generates a <file>.changes</file> file.
2391 </p>
2394 It should not exist in a shipped source package, and so it
2395 (and any backup files or temporary files such as
2396 <file>files.new</file><footnote>
2397 <file>files.new</file> is used as a temporary file by
2398 <prgn>dpkg-gencontrol</prgn> and
2399 <prgn>dpkg-distaddfile</prgn> - they write a new
2400 version of <tt>files</tt> here before renaming it,
2401 to avoid leaving a corrupted copy if an error
2402 occurs.
2403 </footnote>) should be removed by the
2404 <tt>clean</tt> target. It may also be wise to
2405 ensure a fresh start by emptying or removing it at the
2406 start of the <tt>binary</tt> target.
2407 </p>
2410 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2411 package, it adds an entry to <file>debian/files</file> for the
2412 <file>.deb</file> file that will be created when <tt>dpkg-deb
2413 --build</tt> is run for that binary package. So for most
2414 packages all that needs to be done with this file is to
2415 delete it in the <tt>clean</tt> target.
2416 </p>
2419 If a package upload includes files besides the source
2420 package and any binary packages whose control files were
2421 made with <prgn>dpkg-gencontrol</prgn> then they should be
2422 placed in the parent of the package's top-level directory
2423 and <prgn>dpkg-distaddfile</prgn> should be called to add
2424 the file to the list in <file>debian/files</file>.</p>
2425 </sect>
2427 <sect id="embeddedfiles">
2428 <heading>Convenience copies of code</heading>
2431 Some software packages include in their distribution convenience
2432 copies of code from other software packages, generally so that
2433 users compiling from source don't have to download multiple
2434 packages. Debian packages should not make use of these
2435 convenience copies unless the included package is explicitly
2436 intended to be used in this way.<footnote>
2437 For example, parts of the GNU build system work like this.
2438 </footnote>
2439 If the included code is already in the Debian archive in the
2440 form of a library, the Debian packaging should ensure that
2441 binary packages reference the libraries already in Debian and
2442 the convenience copy is not used. If the included code is not
2443 already in Debian, it should be packaged separately as a
2444 prerequisite if possible.
2445 <footnote>
2446 Having multiple copies of the same code in Debian is
2447 inefficient, often creates either static linking or shared
2448 library conflicts, and, most importantly, increases the
2449 difficulty of handling security vulnerabilities in the
2450 duplicated code.
2451 </footnote>
2452 </p>
2453 </sect>
2455 <sect id="readmesource">
2456 <heading>Source package handling:
2457 <file>debian/README.source</file></heading>
2460 If running <prgn>dpkg-source -x</prgn> on a source package
2461 doesn't produce the source of the package, ready for editing,
2462 and allow one to make changes and run
2463 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2464 without taking any additional steps, creating a
2465 <file>debian/README.source</file> documentation file is
2466 recommended. This file should explain how to do all of the
2467 following:
2468 <enumlist>
2469 <item>Generate the fully patched source, in a form ready for
2470 editing, that would be built to create Debian
2471 packages. Doing this with a <tt>patch</tt> target in
2472 <file>debian/rules</file> is recommended; see
2473 <ref id="debianrules">.</item>
2474 <item>Modify the source and save those modifications so that
2475 they will be applied when building the package.</item>
2476 <item>Remove source modifications that are currently being
2477 applied when building the package.</item>
2478 <item>Optionally, document what steps are necessary to
2479 upgrade the Debian source package to a new upstream version,
2480 if applicable.</item>
2481 </enumlist>
2482 This explanation should include specific commands and mention
2483 any additional required Debian packages. It should not assume
2484 familiarity with any specific Debian packaging system or patch
2485 management tools.
2486 </p>
2489 This explanation may refer to a documentation file installed by
2490 one of the package's build dependencies provided that the
2491 referenced documentation clearly explains these tasks and is not
2492 a general reference manual.
2493 </p>
2496 <file>debian/README.source</file> may also include any other
2497 information that would be helpful to someone modifying the
2498 source package. Even if the package doesn't fit the above
2499 description, maintainers are encouraged to document in a
2500 <file>debian/README.source</file> file any source package with a
2501 particularly complex or unintuitive source layout or build
2502 system (for example, a package that builds the same source
2503 multiple times to generate different binary packages).
2504 </p>
2505 </sect>
2506 </chapt>
2509 <chapt id="controlfields">
2510 <heading>Control files and their fields</heading>
2513 The package management system manipulates data represented in
2514 a common format, known as <em>control data</em>, stored in
2515 <em>control files</em>.
2516 Control files are used for source packages, binary packages and
2517 the <file>.changes</file> files which control the installation
2518 of uploaded files<footnote>
2519 <prgn>dpkg</prgn>'s internal databases are in a similar
2520 format.
2521 </footnote>.
2522 </p>
2524 <sect id="controlsyntax">
2525 <heading>Syntax of control files</heading>
2528 A control file consists of one or more paragraphs of
2529 fields<footnote>
2530 The paragraphs are also sometimes referred to as stanzas.
2531 </footnote>.
2532 The paragraphs are separated by empty lines. Parsers may accept
2533 lines consisting solely of spaces and tabs as paragraph
2534 separators, but control files should use empty lines. Some control
2535 files allow only one paragraph; others allow several, in
2536 which case each paragraph usually refers to a different
2537 package. (For example, in source packages, the first
2538 paragraph refers to the source package, and later paragraphs
2539 refer to binary packages generated from the source.) The
2540 ordering of the paragraphs in control files is significant.
2541 </p>
2544 Each paragraph consists of a series of data fields. Each field
2545 consists of the field name followed by a colon and then the
2546 data/value associated with that field. The field name is
2547 composed of US-ASCII characters excluding control characters,
2548 space, and colon (i.e., characters in the ranges 33-57 and
2549 59-126, inclusive). Field names must not begin with the comment
2550 character, <tt>#</tt>, nor with the hyphen character, <tt>-</tt>.
2551 </p>
2554 The field ends at the end of the line or at the end of the last
2555 continuation line (see below). Horizontal whitespace (spaces
2556 and tabs) may occur immediately before or after the value and is
2557 ignored there; it is conventional to put a single space after
2558 the colon. For example, a field might be:
2559 <example compact="compact">
2560 Package: libc6
2561 </example>
2562 the field name is <tt>Package</tt> and the field value
2563 <tt>libc6</tt>.
2564 </p>
2565 <p> Empty field values are only permitted in source package control files
2566 (<file>debian/control</file>). Such fields are ignored.
2567 </p>
2569 A paragraph must not contain more than one instance of a
2570 particular field name.
2571 </p>
2574 There are three types of fields:
2575 <taglist>
2576 <tag>simple</tag>
2577 <item>
2578 The field, including its value, must be a single line. Folding
2579 of the field is not permitted. This is the default field type
2580 if the definition of the field does not specify a different
2581 type.
2582 </item>
2583 <tag>folded</tag>
2584 <item>
2585 The value of a folded field is a logical line that may span
2586 several lines. The lines after the first are called
2587 continuation lines and must start with a space or a tab.
2588 Whitespace, including any newlines, is not significant in the
2589 field values of folded fields.<footnote>
2590 This folding method is similar to RFC 5322, allowing control
2591 files that contain only one paragraph and no multiline fields
2592 to be read by parsers written for RFC 5322.
2593 </footnote>
2594 </item>
2595 <tag>multiline</tag>
2596 <item>
2597 The value of a multiline field may comprise multiple continuation
2598 lines. The first line of the value, the part on the same line as
2599 the field name, often has special significance or may have to be
2600 empty. Other lines are added following the same syntax as the
2601 continuation lines of the folded fields. Whitespace, including newlines,
2602 is significant in the values of multiline fields.
2603 </item>
2604 </taglist>
2605 </p>
2608 Whitespace must not appear
2609 inside names (of packages, architectures, files or anything
2610 else) or version numbers, or between the characters of
2611 multi-character version relationships.
2612 </p>
2615 The presence and purpose of a field, and the syntax of its
2616 value may differ between types of control files.
2617 </p>
2620 Field names are not case-sensitive, but it is usual to
2621 capitalize the field names using mixed case as shown below.
2622 Field values are case-sensitive unless the description of the
2623 field says otherwise.
2624 </p>
2627 Paragraph separators (empty lines) and lines consisting only of
2628 spaces and tabs are not allowed within field values or between
2629 fields. Empty lines in field values are usually escaped by
2630 representing them by a space followed by a dot.
2631 </p>
2634 Lines starting with # without any preceding whitespace are comments
2635 lines that are only permitted in source package control files
2636 (<file>debian/control</file>). These comment lines are ignored, even
2637 between two continuation lines. They do not end logical lines.
2638 </p>
2641 All control files must be encoded in UTF-8.
2642 </p>
2643 </sect>
2645 <sect id="sourcecontrolfiles">
2646 <heading>Source package control files -- <file>debian/control</file></heading>
2649 The <file>debian/control</file> file contains the most vital
2650 (and version-independent) information about the source package
2651 and about the binary packages it creates.
2652 </p>
2655 The first paragraph of the control file contains information about
2656 the source package in general. The subsequent sets each describe a
2657 binary package that the source tree builds.
2658 </p>
2661 The fields in the general paragraph (the first one, for the source
2662 package) are:
2664 <list compact="compact">
2665 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2666 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2667 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2668 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2669 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2670 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2671 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2672 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2673 <item><qref id="f-VCS-fields"><tt>Vcs-Browser</tt>, <tt>Vcs-Git</tt>, et al.</qref></item>
2674 </list>
2675 </p>
2678 The fields in the binary package paragraphs are:
2680 <list compact="compact">
2681 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2682 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2683 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2684 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2685 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2686 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2687 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2688 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2689 <item><qref id="built-using"><tt>Built-Using</tt></qref></item>
2690 <item><qref id="f-Package-Type"><tt>Package-Type</tt></qref></item>
2691 </list>
2692 </p>
2695 The syntax and semantics of the fields are described below.
2696 </p>
2699 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2700 generate control files for binary packages (see below), by
2701 <prgn>dpkg-genchanges</prgn> to generate the
2702 <file>.changes</file> file to accompany the upload, and by
2703 <prgn>dpkg-source</prgn> when it creates the
2704 <file>.dsc</file> source control file as part of a source
2705 archive. Some fields are folded in <file>debian/control</file>,
2706 but not in any other control
2707 file. These tools are responsible for removing the line
2708 breaks from such fields when using fields from
2709 <file>debian/control</file> to generate other control files.
2710 They are also responsible for discarding empty fields.
2711 </p>
2714 The fields here may contain variable references - their
2715 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2716 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2717 when they generate output control files.
2718 See <ref id="substvars"> for details.
2719 </p>
2720 </sect>
2722 <sect id="binarycontrolfiles">
2723 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2726 The <file>DEBIAN/control</file> file contains the most vital
2727 (and version-dependent) information about a binary package. It
2728 consists of a single paragraph.
2729 </p>
2732 The fields in this file are:
2734 <list compact="compact">
2735 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2736 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2737 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2738 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2739 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2740 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2741 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2742 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2743 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2744 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2745 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2746 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2747 <item><qref id="built-using"><tt>Built-Using</tt></qref></item>
2748 </list>
2749 </p>
2750 </sect>
2752 <sect id="debiansourcecontrolfiles">
2753 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2756 This file consists of a single paragraph, possibly surrounded by
2757 a PGP signature. The fields of that paragraph are listed below.
2758 Their syntax is described above, in <ref id="controlsyntax">.
2760 <list compact="compact">
2761 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2762 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2763 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2764 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2765 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2766 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2767 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2768 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2769 <item><qref id="f-VCS-fields"><tt>Vcs-Browser</tt>, <tt>Vcs-Git</tt>, et al.</qref></item>
2770 <item><qref id="f-Dgit"><tt>Dgit</tt></qref></item>
2771 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2772 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2773 <item><qref id="f-Package-List"><tt>Package-List</tt></qref> (recommended)</item>
2774 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2775 and <tt>Checksums-Sha256</tt></qref> (mandatory)</item>
2776 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2777 </list>
2778 </p>
2781 The Debian source control file is generated by
2782 <prgn>dpkg-source</prgn> when it builds the source
2783 archive, from other files in the source package,
2784 described above. When unpacking, it is checked against
2785 the files and directories in the other parts of the
2786 source package.
2787 </p>
2789 </sect>
2791 <sect id="debianchangesfiles">
2792 <heading>Debian changes files -- <file>.changes</file></heading>
2795 The <file>.changes</file> files are used by the Debian archive
2796 maintenance software to process updates to packages. They
2797 consist of a single paragraph, possibly surrounded by a PGP
2798 signature. That paragraph contains information from the
2799 <file>debian/control</file> file and other data about the
2800 source package gathered via <file>debian/changelog</file>
2801 and <file>debian/rules</file>.
2802 </p>
2805 <file>.changes</file> files have a format version that is
2806 incremented whenever the documented fields or their meaning
2807 change. This document describes format &changesversion;.
2808 </p>
2811 The fields in this file are:
2813 <list compact="compact">
2814 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2815 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2816 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2817 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2818 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2819 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2820 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2821 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2822 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2823 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2824 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2825 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2826 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2827 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2828 and <tt>Checksums-Sha256</tt></qref> (mandatory)</item>
2829 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2830 </list>
2831 </p>
2832 </sect>
2834 <sect id="controlfieldslist">
2835 <heading>List of fields</heading>
2837 <sect1 id="f-Source">
2838 <heading><tt>Source</tt></heading>
2841 This field identifies the source package name.
2842 </p>
2845 In <file>debian/control</file> or a <file>.dsc</file> file,
2846 this field must contain only the name of the source package.
2847 </p>
2850 In a binary package control file or a <file>.changes</file>
2851 file, the source package name may be followed by a version
2852 number in parentheses<footnote>
2853 It is customary to leave a space after the package name
2854 if a version number is specified.
2855 </footnote>.
2856 This version number may be omitted (and is, by
2857 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2858 the <tt>Version</tt> field of the binary package in
2859 question. The field itself may be omitted from a binary
2860 package control file when the source package has the same
2861 name and version as the binary package.
2862 </p>
2865 Package names (both source and binary,
2866 see <ref id="f-Package">) must consist only of lower case
2867 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2868 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2869 (<tt>.</tt>). They must be at least two characters long and
2870 must start with an alphanumeric character.
2871 </p>
2872 </sect1>
2874 <sect1 id="f-Maintainer">
2875 <heading><tt>Maintainer</tt></heading>
2878 The package maintainer's name and email address. The name
2879 must come first, then the email address inside angle
2880 brackets <tt>&lt;&gt;</tt> (in RFC822 format).
2881 </p>
2884 If the maintainer's name contains a full stop then the
2885 whole field will not work directly as an email address due
2886 to a misfeature in the syntax specified in RFC822; a
2887 program using this field as an address must check for this
2888 and correct the problem if necessary (for example by
2889 putting the name in round brackets and moving it to the
2890 end, and bringing the email address forward).
2891 </p>
2894 See <ref id="maintainer"> for additional requirements and
2895 information about package maintainers.
2896 </p>
2897 </sect1>
2899 <sect1 id="f-Uploaders">
2900 <heading><tt>Uploaders</tt></heading>
2903 List of the names and email addresses of co-maintainers of the
2904 package, if any. If the package has other maintainers besides
2905 the one named in the <qref id="f-Maintainer">Maintainer
2906 field</qref>, their names and email addresses should be listed
2907 here. The format of each entry is the same as that of the
2908 Maintainer field, and multiple entries must be comma
2909 separated.
2910 </p>
2913 This is normally an optional field, but if
2914 the <tt>Maintainer</tt> control field names a group of people
2915 and a shared email address, the <tt>Uploaders</tt> field must
2916 be present and must contain at least one human with their
2917 personal email address.
2918 </p>
2921 The Uploaders field in <file>debian/control</file> can be folded.
2922 </p>
2923 </sect1>
2925 <sect1 id="f-Changed-By">
2926 <heading><tt>Changed-By</tt></heading>
2929 The name and email address of the person who prepared this
2930 version of the package, usually a maintainer. The syntax is
2931 the same as for the <qref id="f-Maintainer">Maintainer
2932 field</qref>.
2933 </p>
2934 </sect1>
2936 <sect1 id="f-Section">
2937 <heading><tt>Section</tt></heading>
2940 This field specifies an application area into which the package
2941 has been classified. See <ref id="subsections">.
2942 </p>
2945 When it appears in the <file>debian/control</file> file,
2946 it gives the value for the subfield of the same name in
2947 the <tt>Files</tt> field of the <file>.changes</file> file.
2948 It also gives the default for the same field in the binary
2949 packages.
2950 </p>
2951 </sect1>
2953 <sect1 id="f-Priority">
2954 <heading><tt>Priority</tt></heading>
2957 This field represents how important it is that the user
2958 have the package installed. See <ref id="priorities">.
2959 </p>
2962 When it appears in the <file>debian/control</file> file,
2963 it gives the value for the subfield of the same name in
2964 the <tt>Files</tt> field of the <file>.changes</file> file.
2965 It also gives the default for the same field in the binary
2966 packages.
2967 </p>
2968 </sect1>
2970 <sect1 id="f-Package">
2971 <heading><tt>Package</tt></heading>
2974 The name of the binary package.
2975 </p>
2978 Binary package names must follow the same syntax and
2979 restrictions as source package names. See <ref id="f-Source">
2980 for the details.
2981 </p>
2982 </sect1>
2984 <sect1 id="f-Architecture">
2985 <heading><tt>Architecture</tt></heading>
2988 Depending on context and the control file used, the
2989 <tt>Architecture</tt> field can include the following sets of
2990 values:
2991 <list>
2992 <item>
2993 A unique single word identifying a Debian machine
2994 architecture as described in <ref id="arch-spec">.
2995 </item>
2996 <item>
2997 An architecture wildcard identifying a set of Debian
2998 machine architectures, see <ref id="arch-wildcard-spec">.
2999 <tt>any</tt> matches all Debian machine architectures
3000 and is the most frequently used.
3001 </item>
3002 <item>
3003 <tt>all</tt>, which indicates an
3004 architecture-independent package.
3005 </item>
3006 <item>
3007 <tt>source</tt>, which indicates a source package.
3008 </item>
3009 </list>
3010 </p>
3013 In the main <file>debian/control</file> file in the source
3014 package, this field may contain the special
3015 value <tt>all</tt>, the special architecture
3016 wildcard <tt>any</tt>, or a list of specific and wildcard
3017 architectures separated by spaces. If <tt>all</tt>
3018 or <tt>any</tt> appears, that value must be the entire
3019 contents of the field. Most packages will use
3020 either <tt>all</tt> or <tt>any</tt>.
3021 </p>
3024 Specifying a specific list of architectures indicates that the
3025 source will build an architecture-dependent package only on
3026 architectures included in the list. Specifying a list of
3027 architecture wildcards indicates that the source will build an
3028 architecture-dependent package on only those architectures
3029 that match any of the specified architecture wildcards.
3030 Specifying a list of architectures or architecture wildcards
3031 other than <tt>any</tt> is for the minority of cases where a
3032 program is not portable or is not useful on some
3033 architectures. Where possible, the program should be made
3034 portable instead.
3035 </p>
3038 In the Debian source control file <file>.dsc</file>, this
3039 field contains a list of architectures and architecture
3040 wildcards separated by spaces. When the list contains the
3041 architecture wildcard <tt>any</tt>, the only other value
3042 allowed in the list is <tt>all</tt>.
3043 </p>
3046 The list may include (or consist solely of) the special
3047 value <tt>all</tt>. In other words, in <file>.dsc</file>
3048 files unlike the <file>debian/control</file>, <tt>all</tt> may
3049 occur in combination with specific architectures.
3050 The <tt>Architecture</tt> field in the Debian source control
3051 file <file>.dsc</file> is generally constructed from
3052 the <tt>Architecture</tt> fields in
3053 the <file>debian/control</file> in the source package.
3054 </p>
3057 Specifying only <tt>any</tt> indicates that the source package
3058 isn't dependent on any particular architecture and should
3059 compile fine on any one. The produced binary package(s)
3060 will be specific to whatever the current build architecture is.
3061 </p>
3064 Specifying only <tt>all</tt> indicates that the source package
3065 will only build architecture-independent packages.
3066 </p>
3069 Specifying <tt>any all</tt> indicates that the source package
3070 isn't dependent on any particular architecture. The set of
3071 produced binary packages will include at least one
3072 architecture-dependant package and one architecture-independent
3073 package.
3074 </p>
3077 Specifying a list of architectures or architecture wildcards
3078 indicates that the source will build an architecture-dependent
3079 package, and will only work correctly on the listed or
3080 matching architectures. If the source package also builds at
3081 least one architecture-independent package, <tt>all</tt> will
3082 also be included in the list.
3083 </p>
3086 In a <file>.changes</file> file, the <tt>Architecture</tt>
3087 field lists the architecture(s) of the package(s) currently
3088 being uploaded. This will be a list; if the source for the
3089 package is also being uploaded, the special
3090 entry <tt>source</tt> is also present. <tt>all</tt> will be
3091 present if any architecture-independent packages are being
3092 uploaded. Architecture wildcards such as <tt>any</tt> must
3093 never occur in the <tt>Architecture</tt> field in
3094 the <file>.changes</file> file.
3095 </p>
3098 See <ref id="debianrules"> for information on how to get
3099 the architecture for the build process.
3100 </p>
3101 </sect1>
3103 <sect1 id="f-Essential">
3104 <heading><tt>Essential</tt></heading>
3107 This is a boolean field which may occur only in the
3108 control file of a binary package or in a per-package fields
3109 paragraph of a source package control file.
3110 </p>
3113 If set to <tt>yes</tt> then the package management system
3114 will refuse to remove the package (upgrading and replacing
3115 it is still possible). The other possible value is <tt>no</tt>,
3116 which is the same as not having the field at all.
3117 </p>
3118 </sect1>
3120 <sect1>
3121 <heading>Package interrelationship fields:
3122 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
3123 <tt>Recommends</tt>, <tt>Suggests</tt>,
3124 <tt>Breaks</tt>, <tt>Conflicts</tt>,
3125 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
3126 </heading>
3129 These fields describe the package's relationships with
3130 other packages. Their syntax and semantics are described
3131 in <ref id="relationships">.</p>
3132 </sect1>
3134 <sect1 id="f-Standards-Version">
3135 <heading><tt>Standards-Version</tt></heading>
3138 The most recent version of the standards (the policy
3139 manual and associated texts) with which the package
3140 complies.
3141 </p>
3144 The version number has four components: major and minor
3145 version number and major and minor patch level. When the
3146 standards change in a way that requires every package to
3147 change the major number will be changed. Significant
3148 changes that will require work in many packages will be
3149 signaled by a change to the minor number. The major patch
3150 level will be changed for any change to the meaning of the
3151 standards, however small; the minor patch level will be
3152 changed when only cosmetic, typographical or other edits
3153 are made which neither change the meaning of the document
3154 nor affect the contents of packages.
3155 </p>
3158 Thus only the first three components of the policy version
3159 are significant in the <em>Standards-Version</em> control
3160 field, and so either these three components or all four
3161 components may be specified.<footnote>
3162 In the past, people specified the full version number
3163 in the Standards-Version field, for example "2.3.0.0".
3164 Since minor patch-level changes don't introduce new
3165 policy, it was thought it would be better to relax
3166 policy and only require the first 3 components to be
3167 specified, in this example "2.3.0". All four
3168 components may still be used if someone wishes to do so.
3169 </footnote>
3170 </p>
3172 </sect1>
3174 <sect1 id="f-Version">
3175 <heading><tt>Version</tt></heading>
3178 The version number of a package. The format is:
3179 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3180 </p>
3183 The three components here are:
3184 <taglist>
3185 <tag><var>epoch</var></tag>
3186 <item>
3188 This is a single (generally small) unsigned integer. It
3189 may be omitted, in which case zero is assumed. If it is
3190 omitted then the <var>upstream_version</var> may not
3191 contain any colons.
3192 </p>
3195 It is provided to allow mistakes in the version numbers
3196 of older versions of a package, and also a package's
3197 previous version numbering schemes, to be left behind.
3198 </p>
3199 </item>
3201 <tag><var>upstream_version</var></tag>
3202 <item>
3204 This is the main part of the version number. It is
3205 usually the version number of the original ("upstream")
3206 package from which the <file>.deb</file> file has been made,
3207 if this is applicable. Usually this will be in the same
3208 format as that specified by the upstream author(s);
3209 however, it may need to be reformatted to fit into the
3210 package management system's format and comparison
3211 scheme.
3212 </p>
3215 The comparison behavior of the package management system
3216 with respect to the <var>upstream_version</var> is
3217 described below. The <var>upstream_version</var>
3218 portion of the version number is mandatory.
3219 </p>
3222 The <var>upstream_version</var> may contain only
3223 alphanumerics<footnote>
3224 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3225 </footnote>
3226 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3227 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3228 tilde) and should start with a digit. If there is no
3229 <var>debian_revision</var> then hyphens are not allowed;
3230 if there is no <var>epoch</var> then colons are not
3231 allowed.
3232 </p>
3233 </item>
3235 <tag><var>debian_revision</var></tag>
3236 <item>
3238 This part of the version number specifies the version of
3239 the Debian package based on the upstream version. It
3240 may contain only alphanumerics and the characters
3241 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3242 tilde) and is compared in the same way as the
3243 <var>upstream_version</var> is.
3244 </p>
3247 It is optional; if it isn't present then the
3248 <var>upstream_version</var> may not contain a hyphen.
3249 This format represents the case where a piece of
3250 software was written specifically to be a Debian
3251 package, where the Debian package source must always
3252 be identical to the pristine source and therefore no
3253 revision indication is required.
3254 </p>
3257 It is conventional to restart the
3258 <var>debian_revision</var> at <tt>1</tt> each time the
3259 <var>upstream_version</var> is increased.
3260 </p>
3263 The package management system will break the version
3264 number apart at the last hyphen in the string (if there
3265 is one) to determine the <var>upstream_version</var> and
3266 <var>debian_revision</var>. The absence of a
3267 <var>debian_revision</var> is equivalent to a
3268 <var>debian_revision</var> of <tt>0</tt>.
3269 </p>
3270 </item>
3271 </taglist>
3272 </p>
3275 When comparing two version numbers, first the <var>epoch</var>
3276 of each are compared, then the <var>upstream_version</var> if
3277 <var>epoch</var> is equal, and then <var>debian_revision</var>
3278 if <var>upstream_version</var> is also equal.
3279 <var>epoch</var> is compared numerically. The
3280 <var>upstream_version</var> and <var>debian_revision</var>
3281 parts are compared by the package management system using the
3282 following algorithm:
3283 </p>
3286 The strings are compared from left to right.
3287 </p>
3290 First the initial part of each string consisting entirely of
3291 non-digit characters is determined. These two parts (one of
3292 which may be empty) are compared lexically. If a difference
3293 is found it is returned. The lexical comparison is a
3294 comparison of ASCII values modified so that all the letters
3295 sort earlier than all the non-letters and so that a tilde
3296 sorts before anything, even the end of a part. For example,
3297 the following parts are in sorted order from earliest to
3298 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3299 <tt>a</tt>.<footnote>
3300 One common use of <tt>~</tt> is for upstream pre-releases.
3301 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3302 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3303 </footnote>
3304 </p>
3307 Then the initial part of the remainder of each string which
3308 consists entirely of digit characters is determined. The
3309 numerical values of these two parts are compared, and any
3310 difference found is returned as the result of the comparison.
3311 For these purposes an empty string (which can only occur at
3312 the end of one or both version strings being compared) counts
3313 as zero.
3314 </p>
3317 These two steps (comparing and removing initial non-digit
3318 strings and initial digit strings) are repeated until a
3319 difference is found or both strings are exhausted.
3320 </p>
3323 Note that the purpose of epochs is to allow us to leave behind
3324 mistakes in version numbering, and to cope with situations
3325 where the version numbering scheme changes. It is
3326 <em>not</em> intended to cope with version numbers containing
3327 strings of letters which the package management system cannot
3328 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3329 silly orderings.<footnote>
3330 The author of this manual has heard of a package whose
3331 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3332 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3333 forth.
3334 </footnote>
3335 </p>
3336 </sect1>
3338 <sect1 id="f-Description">
3339 <heading><tt>Description</tt></heading>
3342 In a source or binary control file, the <tt>Description</tt>
3343 field contains a description of the binary package, consisting
3344 of two parts, the synopsis or the short description, and the
3345 long description. It is a multiline field with the following
3346 format:
3347 </p>
3350 <example>
3351 Description: &lt;single line synopsis&gt;
3352 &lt;extended description over several lines&gt;
3353 </example>
3354 </p>
3357 The lines in the extended description can have these formats:
3358 </p>
3360 <p><list>
3362 <item>
3363 Those starting with a single space are part of a paragraph.
3364 Successive lines of this form will be word-wrapped when
3365 displayed. The leading space will usually be stripped off.
3366 The line must contain at least one non-whitespace character.
3367 </item>
3369 <item>
3370 Those starting with two or more spaces. These will be
3371 displayed verbatim. If the display cannot be panned
3372 horizontally, the displaying program will line wrap them "hard"
3373 (i.e., without taking account of word breaks). If it can they
3374 will be allowed to trail off to the right. None, one or two
3375 initial spaces may be deleted, but the number of spaces
3376 deleted from each line will be the same (so that you can have
3377 indenting work correctly, for example). The line must
3378 contain at least one non-whitespace character.
3379 </item>
3381 <item>
3382 Those containing a single space followed by a single full stop
3383 character. These are rendered as blank lines. This is the
3384 <em>only</em> way to get a blank line<footnote>
3385 Completely empty lines will not be rendered as blank lines.
3386 Instead, they will cause the parser to think you're starting
3387 a whole new record in the control file, and will therefore
3388 likely abort with an error.
3389 </footnote>.
3390 </item>
3392 <item>
3393 Those containing a space, a full stop and some more characters.
3394 These are for future expansion. Do not use them.
3395 </item>
3397 </list></p>
3400 Do not use tab characters. Their effect is not predictable.
3401 </p>
3404 See <ref id="descriptions"> for further information on this.
3405 </p>
3408 In a <file>.changes</file> file, the <tt>Description</tt>
3409 field contains a summary of the descriptions for the packages
3410 being uploaded. For this case, the first line of the field
3411 value (the part on the same line as <tt>Description:</tt>) is
3412 always empty. It is a multiline field, with one
3413 line per package. Each line is
3414 indented by one space and contains the name of a binary
3415 package, a space, a hyphen (<tt>-</tt>), a space, and the
3416 short description line from that package.
3417 </p>
3418 </sect1>
3420 <sect1 id="f-Distribution">
3421 <heading><tt>Distribution</tt></heading>
3424 In a <file>.changes</file> file or parsed changelog output
3425 this contains the (space-separated) name(s) of the
3426 distribution(s) where this version of the package should
3427 be installed. Valid distributions are determined by the
3428 archive maintainers.<footnote>
3429 Example distribution names in the Debian archive used in
3430 <file>.changes</file> files are:
3431 <taglist compact="compact">
3432 <tag><em>unstable</em></tag>
3433 <item>
3434 This distribution value refers to the
3435 <em>developmental</em> part of the Debian distribution
3436 tree. Most new packages, new upstream versions of
3437 packages and bug fixes go into the <em>unstable</em>
3438 directory tree.
3439 </item>
3441 <tag><em>experimental</em></tag>
3442 <item>
3443 The packages with this distribution value are deemed
3444 by their maintainers to be high risk. Oftentimes they
3445 represent early beta or developmental packages from
3446 various sources that the maintainers want people to
3447 try, but are not ready to be a part of the other parts
3448 of the Debian distribution tree.
3449 </item>
3450 </taglist>
3453 Others are used for updating stable releases or for
3454 security uploads. More information is available in the
3455 Debian Developer's Reference, section "The Debian
3456 archive".
3457 </p>
3458 </footnote>
3459 The Debian archive software only supports listing a single
3460 distribution. Migration of packages to other distributions is
3461 handled outside of the upload process.
3462 </p>
3463 </sect1>
3465 <sect1 id="f-Date">
3466 <heading><tt>Date</tt></heading>
3469 This field includes the date the package was built or last
3470 edited. It must be in the same format as the <var>date</var>
3471 in a <file>debian/changelog</file> entry.
3472 </p>
3475 The value of this field is usually extracted from the
3476 <file>debian/changelog</file> file - see
3477 <ref id="dpkgchangelog">).
3478 </p>
3479 </sect1>
3481 <sect1 id="f-Format">
3482 <heading><tt>Format</tt></heading>
3485 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3486 files, this field declares the format version of that file.
3487 The syntax of the field value is the same as that of
3488 a <qref id="f-Version">package version number</qref> except
3489 that no epoch or Debian revision is allowed. The format
3490 described in this document is <tt>&changesversion;</tt>.
3491 </p>
3494 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3495 Debian source control</qref> files, this field declares the
3496 format of the source package. The field value is used by
3497 programs acting on a source package to interpret the list of
3498 files in the source package and determine how to unpack it.
3499 The syntax of the field value is a numeric major revision, a
3500 period, a numeric minor revision, and then an optional subtype
3501 after whitespace, which if specified is an alphanumeric word
3502 in parentheses. The subtype is optional in the syntax but may
3503 be mandatory for particular source format revisions.
3504 <footnote>
3505 The source formats currently supported by the Debian archive
3506 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3507 and <tt>3.0 (quilt)</tt>.
3508 </footnote>
3509 </p>
3510 </sect1>
3512 <sect1 id="f-Urgency">
3513 <heading><tt>Urgency</tt></heading>
3516 This is a description of how important it is to upgrade to
3517 this version from previous ones. It consists of a single
3518 keyword taking one of the values <tt>low</tt>,
3519 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3520 <tt>critical</tt><footnote>
3521 Other urgency values are supported with configuration
3522 changes in the archive software but are not used in Debian.
3523 The urgency affects how quickly a package will be considered
3524 for inclusion into the <tt>testing</tt> distribution and
3525 gives an indication of the importance of any fixes included
3526 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3527 treated as synonymous.
3528 </footnote> (not case-sensitive) followed by an optional
3529 commentary (separated by a space) which is usually in
3530 parentheses. For example:
3532 <example>
3533 Urgency: low (HIGH for users of diversions)
3534 </example>
3536 </p>
3539 The value of this field is usually extracted from the
3540 <file>debian/changelog</file> file - see
3541 <ref id="dpkgchangelog">.
3542 </p>
3543 </sect1>
3545 <sect1 id="f-Changes">
3546 <heading><tt>Changes</tt></heading>
3549 This multiline field contains the human-readable changes data, describing
3550 the differences between the last version and the current one.
3551 </p>
3554 The first line of the field value (the part on the same line
3555 as <tt>Changes:</tt>) is always empty. The content of the
3556 field is expressed as continuation lines, with each line
3557 indented by at least one space. Blank lines must be
3558 represented by a line consisting only of a space and a full
3559 stop (<tt>.</tt>).
3560 </p>
3563 The value of this field is usually extracted from the
3564 <file>debian/changelog</file> file - see
3565 <ref id="dpkgchangelog">).
3566 </p>
3569 Each version's change information should be preceded by a
3570 "title" line giving at least the version, distribution(s)
3571 and urgency, in a human-readable way.
3572 </p>
3575 If data from several versions is being returned the entry
3576 for the most recent version should be returned first, and
3577 entries should be separated by the representation of a
3578 blank line (the "title" line may also be followed by the
3579 representation of a blank line).
3580 </p>
3581 </sect1>
3583 <sect1 id="f-Binary">
3584 <heading><tt>Binary</tt></heading>
3587 This folded field is a list of binary packages. Its syntax and
3588 meaning varies depending on the control file in which it
3589 appears.
3590 </p>
3593 When it appears in the <file>.dsc</file> file, it lists binary
3594 packages which a source package can produce, separated by
3595 commas<footnote>
3596 A space after each comma is conventional.
3597 </footnote>. The source package
3598 does not necessarily produce all of these binary packages for
3599 every architecture. The source control file doesn't contain
3600 details of which architectures are appropriate for which of
3601 the binary packages.
3602 </p>
3605 When it appears in a <file>.changes</file> file, it lists the
3606 names of the binary packages being uploaded, separated by
3607 whitespace (not commas).
3608 </p>
3609 </sect1>
3611 <sect1 id="f-Installed-Size">
3612 <heading><tt>Installed-Size</tt></heading>
3615 This field appears in the control files of binary packages,
3616 and in the <file>Packages</file> files. It gives an estimate
3617 of the total amount of disk space required to install the
3618 named package. Actual installed size may vary based on block
3619 size, file system properties, or actions taken by package
3620 maintainer scripts.
3621 </p>
3624 The disk space is given as the integer value of the estimated
3625 installed size in bytes, divided by 1024 and rounded up.
3626 </p>
3627 </sect1>
3629 <sect1 id="f-Files">
3630 <heading><tt>Files</tt></heading>
3633 This field contains a list of files with information about
3634 each one. The exact information and syntax varies with
3635 the context.
3636 </p>
3639 In all cases, Files is a multiline field. The first line of
3640 the field value (the part on the same line as <tt>Files:</tt>)
3641 is always empty. The content of the field is expressed as
3642 continuation lines, one line per file. Each line must be
3643 indented by one space and contain a number of sub-fields,
3644 separated by spaces, as described below.
3645 </p>
3648 In the <file>.dsc</file> file, each line contains the MD5
3649 checksum, size and filename of the tar file and (if
3650 applicable) diff file which make up the remainder of the
3651 source package<footnote>
3652 That is, the parts which are not the <tt>.dsc</tt>.
3653 </footnote>. For example:
3654 <example>
3655 Files:
3656 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3657 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3658 </example>
3659 The exact forms of the filenames are described
3660 in <ref id="pkg-sourcearchives">.
3661 </p>
3664 In the <file>.changes</file> file this contains one line per
3665 file being uploaded. Each line contains the MD5 checksum,
3666 size, section and priority and the filename. For example:
3667 <example>
3668 Files:
3669 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3670 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3671 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3672 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3673 </example>
3674 The <qref id="f-Section">section</qref>
3675 and <qref id="f-Priority">priority</qref> are the values of
3676 the corresponding fields in the main source control file. If
3677 no section or priority is specified then <tt>-</tt> should be
3678 used, though section and priority values must be specified for
3679 new packages to be installed properly.
3680 </p>
3683 The special value <tt>byhand</tt> for the section in a
3684 <tt>.changes</tt> file indicates that the file in question
3685 is not an ordinary package file and must be installed by
3686 hand by the distribution maintainers. If the section is
3687 <tt>byhand</tt> the priority should be <tt>-</tt>.
3688 </p>
3691 If a new Debian revision of a package is being shipped and
3692 no new original source archive is being distributed the
3693 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3694 entry for the original source archive
3695 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3696 but the <file>.changes</file> file should leave it out. In
3697 this case the original source archive on the distribution
3698 site must match exactly, byte-for-byte, the original
3699 source archive which was used to generate the
3700 <file>.dsc</file> file and diff which are being uploaded.</p>
3701 </sect1>
3703 <sect1 id="f-Closes">
3704 <heading><tt>Closes</tt></heading>
3707 A space-separated list of bug report numbers that the upload
3708 governed by the .changes file closes.
3709 </p>
3710 </sect1>
3712 <sect1 id="f-Homepage">
3713 <heading><tt>Homepage</tt></heading>
3716 The URL of the web site for this package, preferably (when
3717 applicable) the site from which the original source can be
3718 obtained and any additional upstream documentation or
3719 information may be found. The content of this field is a
3720 simple URL without any surrounding characters such as
3721 <tt>&lt;&gt;</tt>.
3722 </p>
3723 </sect1>
3725 <sect1 id="f-Checksums">
3726 <heading><tt>Checksums-Sha1</tt>
3727 and <tt>Checksums-Sha256</tt></heading>
3730 These multiline fields contain a list of files with a checksum and size
3731 for each one. Both <tt>Checksums-Sha1</tt>
3732 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3733 only in the checksum algorithm used: SHA-1
3734 for <tt>Checksums-Sha1</tt> and SHA-256
3735 for <tt>Checksums-Sha256</tt>.
3736 </p>
3739 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3740 multiline fields. The first line of the field value (the part
3741 on the same line as <tt>Checksums-Sha1:</tt>
3742 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3743 of the field is expressed as continuation lines, one line per
3744 file. Each line consists of the checksum, a space, the file
3745 size, a space, and the file name. For example (from
3746 a <file>.changes</file> file):
3747 <example>
3748 Checksums-Sha1:
3749 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3750 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3751 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3752 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3753 Checksums-Sha256:
3754 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3755 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3756 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3757 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3758 </example>
3759 </p>
3762 In the <file>.dsc</file> file, these fields list all
3763 files that make up the source package. In
3764 the <file>.changes</file> file, these fields list all
3765 files being uploaded. The list of files in these fields
3766 must match the list of files in the <tt>Files</tt> field.
3767 </p>
3768 </sect1>
3770 <sect1>
3771 <heading><tt>DM-Upload-Allowed</tt></heading>
3774 Obsolete, see <qref id="f-DM-Upload-Allowed">below</qref>.
3775 </p>
3776 </sect1>
3778 <sect1 id="f-VCS-fields">
3779 <heading>Version Control System (VCS) fields</heading>
3782 Debian source packages are increasingly developed using VCSs. The
3783 purpose of the following fields is to indicate a publicly accessible
3784 repository where the Debian source package is developed.
3786 <taglist>
3787 <tag><tt>Vcs-Browser</tt></tag>
3788 <item>
3790 URL of a web interface for browsing the repository.
3791 </p>
3792 </item>
3794 <tag>
3795 <tt>Vcs-Arch</tt>, <tt>Vcs-Bzr</tt> (Bazaar), <tt>Vcs-Cvs</tt>,
3796 <tt>Vcs-Darcs</tt>, <tt>Vcs-Git</tt>, <tt>Vcs-Hg</tt>
3797 (Mercurial), <tt>Vcs-Mtn</tt> (Monotone), <tt>Vcs-Svn</tt>
3798 (Subversion)
3799 </tag>
3800 <item>
3802 The field name identifies the VCS. The field's value uses the
3803 version control system's conventional syntax for describing
3804 repository locations and should be sufficient to locate the
3805 repository used for packaging. Ideally, it also locates the
3806 branch used for development of new versions of the Debian
3807 package.
3808 </p>
3810 In the case of Git, the value consists of a URL, optionally
3811 followed by the word <tt>-b</tt> and the name of a branch in
3812 the indicated repository, following the syntax of the
3813 <tt>git clone</tt> command. If no branch is specified, the
3814 packaging should be on the default branch.
3815 </p>
3817 More than one different VCS may be specified for the same
3818 package.
3819 </p>
3820 </item>
3821 </taglist>
3822 </p>
3823 </sect1>
3825 <sect1 id="f-Package-List">
3826 <heading><tt>Package-List</tt></heading>
3829 Multiline field listing all the packages that can be built from
3830 the source package, considering every architecture. The first line
3831 of the field value is empty. Each one of the next lines describes
3832 one binary package, by listing its name, type, section and priority
3833 separated by spaces. Fifth and subsequent space-separated items
3834 may be present and parsers must allow them. See the
3835 <qref id="f-Package-Type">Package-Type</qref> field for a list of
3836 package types.
3837 </p>
3838 </sect1>
3840 <sect1 id="f-Package-Type">
3841 <heading><tt>Package-Type</tt></heading>
3844 Simple field containing a word indicating the type of package:
3845 <tt>deb</tt> for binary packages and <tt>udeb</tt> for micro binary
3846 packages. Other types not defined here may be indicated. In
3847 source package control files, the <tt>Package-Type</tt> field
3848 should be omitted instead of giving it a value of <tt>deb</tt>, as
3849 this value is assumed for paragraphs lacking this field.
3850 </p>
3851 </sect1>
3853 <sect1 id="f-Dgit">
3854 <heading><tt>Dgit</tt></heading>
3857 Folded field containing a single git commit hash, presented in
3858 full, followed optionally by whitespace and other data to be
3859 defined in future extensions.
3860 </p>
3863 Declares that the source package corresponds exactly to a
3864 referenced commit in a Git repository available at the canonical
3865 location called <em>dgit-repos</em>, used by <prgn>dgit</prgn>, a
3866 bidirectional gateway between the Debian archive and Git. The
3867 commit is reachable from at least one reference whose name matches
3868 <tt>refs/dgit/*</tt>. See the manual page of <prgn>dgit</prgn> for
3869 further details.
3870 </p>
3871 </sect1>
3872 </sect>
3874 <sect>
3875 <heading>User-defined fields</heading>
3878 Additional user-defined fields may be added to the
3879 source package control file. Such fields will be
3880 ignored, and not copied to (for example) binary or
3881 Debian source control files or upload control files.
3882 </p>
3885 If you wish to add additional unsupported fields to
3886 these output files you should use the mechanism
3887 described here.
3888 </p>
3891 Fields in the main source control information file with
3892 names starting <tt>X</tt>, followed by one or more of
3893 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3894 be copied to the output files. Only the part of the
3895 field name after the hyphen will be used in the output
3896 file. Where the letter <tt>B</tt> is used the field
3897 will appear in binary package control files, where the
3898 letter <tt>S</tt> is used in Debian source control
3899 files and where <tt>C</tt> is used in upload control
3900 (<tt>.changes</tt>) files.
3901 </p>
3904 For example, if the main source information control file
3905 contains the field
3906 <example>
3907 XBS-Comment: I stand between the candle and the star.
3908 </example>
3909 then the binary and Debian source control files will contain the
3910 field
3911 <example>
3912 Comment: I stand between the candle and the star.
3913 </example>
3914 </p>
3916 </sect>
3918 <sect id="obsolete-control-data-fields">
3919 <heading>Obsolete fields</heading>
3922 The following fields have been obsoleted and may be found in packages
3923 conforming with previous versions of the Policy.
3924 </p>
3926 <sect1 id="f-DM-Upload-Allowed">
3927 <heading><tt>DM-Upload-Allowed</tt></heading>
3930 Indicates that Debian Maintainers may upload this package to
3931 the Debian archive. The only valid value is <tt>yes</tt>. This
3932 field was used to regulate uploads by Debian Maintainers, See the
3933 General Resolution <url id="http://www.debian.org/vote/2007/vote_003"
3934 name="Endorse the concept of Debian Maintainers"> for more details.
3935 </p>
3936 </sect1>
3938 </sect>
3940 </chapt>
3943 <chapt id="maintainerscripts">
3944 <heading>Package maintainer scripts and installation procedure</heading>
3946 <sect>
3947 <heading>Introduction to package maintainer scripts</heading>
3950 It is possible to supply scripts as part of a package which
3951 the package management system will run for you when your
3952 package is installed, upgraded or removed.
3953 </p>
3956 These scripts are the control information
3957 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3958 and <prgn>postrm</prgn>. They must be proper executable files;
3959 if they are scripts (which is recommended), they must start with
3960 the usual <tt>#!</tt> convention. They should be readable and
3961 executable by anyone, and must not be world-writable.
3962 </p>
3965 The package management system looks at the exit status from
3966 these scripts. It is important that they exit with a
3967 non-zero status if there is an error, so that the package
3968 management system can stop its processing. For shell
3969 scripts this means that you <em>almost always</em> need to
3970 use <tt>set -e</tt> (this is usually true when writing shell
3971 scripts, in fact). It is also important, of course, that
3972 they exit with a zero status if everything went well.
3973 </p>
3976 Additionally, packages interacting with users
3977 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3978 should install a <prgn>config</prgn> script as a control
3979 information file. See <ref id="maintscriptprompt"> for details.
3980 </p>
3983 When a package is upgraded a combination of the scripts from
3984 the old and new packages is called during the upgrade
3985 procedure. If your scripts are going to be at all
3986 complicated you need to be aware of this, and may need to
3987 check the arguments to your scripts.
3988 </p>
3991 Broadly speaking the <prgn>preinst</prgn> is called before
3992 (a particular version of) a package is unpacked, and the
3993 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3994 before (a version of) a package is removed and the
3995 <prgn>postrm</prgn> afterwards.
3996 </p>
3999 Programs called from maintainer scripts should not normally
4000 have a path prepended to them. Before installation is
4001 started, the package management system checks to see if the
4002 programs <prgn>ldconfig</prgn>, <prgn>start-stop-daemon</prgn>,
4003 and <prgn>update-rc.d</prgn> can be found via the
4004 <tt>PATH</tt> environment variable. Those programs, and any
4005 other program that one would expect to be in the
4006 <tt>PATH</tt>, should thus be invoked without an absolute
4007 pathname. Maintainer scripts should also not reset the
4008 <tt>PATH</tt>, though they might choose to modify it by
4009 prepending or appending package-specific directories. These
4010 considerations really apply to all shell scripts.</p>
4011 </sect>
4013 <sect id="idempotency">
4014 <heading>Maintainer scripts idempotency</heading>
4017 It is necessary for the error recovery procedures that the
4018 scripts be idempotent. This means that if it is run
4019 successfully, and then it is called again, it doesn't bomb
4020 out or cause any harm, but just ensures that everything is
4021 the way it ought to be. If the first call failed, or
4022 aborted half way through for some reason, the second call
4023 should merely do the things that were left undone the first
4024 time, if any, and exit with a success status if everything
4025 is OK.<footnote>
4026 This is so that if an error occurs, the user interrupts
4027 <prgn>dpkg</prgn> or some other unforeseen circumstance
4028 happens you don't leave the user with a badly-broken
4029 package when <prgn>dpkg</prgn> attempts to repeat the
4030 action.
4031 </footnote>
4032 </p>
4033 </sect>
4035 <sect id="controllingterminal">
4036 <heading>Controlling terminal for maintainer scripts</heading>
4039 Maintainer scripts are not guaranteed to run with a controlling
4040 terminal and may not be able to interact with the user. They
4041 must be able to fall back to noninteractive behavior if no
4042 controlling terminal is available. Maintainer scripts that
4043 prompt via a program conforming to the Debian Configuration
4044 Management Specification (see <ref id="maintscriptprompt">) may
4045 assume that program will handle falling back to noninteractive
4046 behavior.
4047 </p>
4050 For high-priority prompts without a reasonable default answer,
4051 maintainer scripts may abort if there is no controlling
4052 terminal. However, this situation should be avoided if at all
4053 possible, since it prevents automated or unattended installs.
4054 In most cases, users will consider this to be a bug in the
4055 package.
4056 </p>
4057 </sect>
4059 <sect id="exitstatus">
4060 <heading>Exit status</heading>
4063 Each script must return a zero exit status for
4064 success, or a nonzero one for failure, since the package
4065 management system looks for the exit status of these scripts
4066 and determines what action to take next based on that datum.
4067 </p>
4068 </sect>
4070 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
4071 scripts are called
4072 </heading>
4075 What follows is a summary of all the ways in which maintainer
4076 scripts may be called along with what facilities those scripts
4077 may rely on being available at that time. Script names preceded
4078 by <var>new-</var> are the scripts from the new version of a
4079 package being installed, upgraded to, or downgraded to. Script
4080 names preceded by <var>old-</var> are the scripts from the old
4081 version of a package that is being upgraded from or downgraded
4082 from.
4083 </p>
4086 The <prgn>preinst</prgn> script may be called in the following
4087 ways:
4088 <taglist>
4089 <tag><var>new-preinst</var> <tt>install</tt></tag>
4090 <tag><var>new-preinst</var> <tt>install</tt>
4091 <var>old-version</var></tag>
4092 <tag><var>new-preinst</var> <tt>upgrade</tt>
4093 <var>old-version</var></tag>
4094 <item>
4095 The package will not yet be unpacked, so
4096 the <prgn>preinst</prgn> script cannot rely on any files
4097 included in its package. Only essential packages and
4098 pre-dependencies (<tt>Pre-Depends</tt>) may be assumed to be
4099 available. Pre-dependencies will have been configured at
4100 least once, but at the time the <prgn>preinst</prgn> is
4101 called they may only be in an "Unpacked" or "Half-Configured"
4102 state if a previous version of the pre-dependency was
4103 completely configured and has not been removed since then.
4104 </item>
4106 <tag><var>old-preinst</var> <tt>abort-upgrade</tt>
4107 <var>new-version</var></tag>
4108 <item>
4109 Called during error handling of an upgrade that failed after
4110 unpacking the new package because the <tt>postrm
4111 upgrade</tt> action failed. The unpacked files may be
4112 partly from the new version or partly missing, so the script
4113 cannot rely on files included in the package. Package
4114 dependencies may not be available. Pre-dependencies will be
4115 at least "Unpacked" following the same rules as above, except
4116 they may be only "Half-Installed" if an upgrade of the
4117 pre-dependency failed.<footnote>
4118 This can happen if the new version of the package no
4119 longer pre-depends on a package that had been partially
4120 upgraded.
4121 </footnote>
4122 </item>
4123 </taglist>
4124 </p>
4127 The <prgn>postinst</prgn> script may be called in the following
4128 ways:
4129 <taglist>
4130 <tag><var>postinst</var> <tt>configure</tt>
4131 <var>most-recently-configured-version</var></tag>
4132 <item>
4133 The files contained in the package will be unpacked. All
4134 package dependencies will at least be "Unpacked". If there
4135 are no circular dependencies involved, all package
4136 dependencies will be configured. For behavior in the case
4137 of circular dependencies, see the discussion
4138 in <ref id="binarydeps">.
4139 </item>
4141 <tag><var>old-postinst</var> <tt>abort-upgrade</tt>
4142 <var>new-version</var></tag>
4143 <tag><var>conflictor's-postinst</var> <tt>abort-remove</tt>
4144 <tt>in-favour</tt> <var>package</var>
4145 <var>new-version</var></tag>
4146 <tag><var>postinst</var> <tt>abort-remove</tt></tag>
4147 <tag><var>deconfigured's-postinst</var>
4148 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
4149 <var>failed-install-package</var> <var>version</var>
4150 [<tt>removing</tt> <var>conflicting-package</var>
4151 <var>version</var>]</tag>
4152 <item>
4153 The files contained in the package will be unpacked. All
4154 package dependencies will at least be "Half-Installed" and
4155 will have previously been configured and not removed.
4156 However, dependencies may not be configured or even fully
4157 unpacked in some error situations.<footnote>
4158 For example, suppose packages foo and bar are "Installed"
4159 with foo depending on bar. If an upgrade of bar were
4160 started and then aborted, and then an attempt to remove
4161 foo failed because its <prgn>prerm</prgn> script failed,
4162 foo's <tt>postinst abort-remove</tt> would be called with
4163 bar only "Half-Installed".
4164 </footnote>
4165 The <prgn>postinst</prgn> should still attempt any actions
4166 for which its dependencies are required, since they will
4167 normally be available, but consider the correct error
4168 handling approach if those actions fail. Aborting
4169 the <prgn>postinst</prgn> action if commands or facilities
4170 from the package dependencies are not available is often the
4171 best approach.
4172 </item>
4173 </taglist>
4174 </p>
4177 The <prgn>prerm</prgn> script may be called in the following
4178 ways:
4179 <taglist>
4180 <tag><var>prerm</var> <tt>remove</tt></tag>
4181 <tag><var>old-prerm</var>
4182 <tt>upgrade</tt><var>new-version</var></tag>
4183 <tag><var>conflictor's-prerm</var> <tt>remove</tt>
4184 <tt>in-favour</tt> <var>package</var>
4185 <var>new-version</var></tag>
4186 <tag><var>deconfigured's-prerm</var> <tt>deconfigure</tt>
4187 <tt>in-favour</tt> <var>package-being-installed</var>
4188 <var>version</var> [<tt>removing</tt>
4189 <var>conflicting-package</var> <var>version</var>]</tag>
4190 <item>
4191 The package whose <prgn>prerm</prgn> is being called will be
4192 at least "Half-Installed". All package dependencies will at
4193 least be "Half-Installed" and will have previously been
4194 configured and not removed. If there was no error, all
4195 dependencies will at least be "Unpacked", but these actions
4196 may be called in various error states where dependencies are
4197 only "Half-Installed" due to a partial upgrade.
4198 </item>
4200 <tag><var>new-prerm</var> <tt>failed-upgrade</tt>
4201 <var>old-version</var></tag>
4202 <item>
4203 Called during error handling when <tt>prerm upgrade</tt>
4204 fails. The new package will not yet be unpacked, and all
4205 the same constraints as for <tt>preinst upgrade</tt> apply.
4206 </item>
4207 </taglist>
4208 </p>
4211 The <prgn>postrm</prgn> script may be called in the following
4212 ways:
4213 <taglist>
4214 <tag><var>postrm</var> <tt>remove</tt></tag>
4215 <tag><var>postrm</var> <tt>purge</tt></tag>
4216 <tag><var>old-postrm</var> <tt>upgrade</tt>
4217 <var>new-version</var></tag>
4218 <tag><var>disappearer's-postrm</var> <tt>disappear</tt>
4219 <var>overwriter</var> <var>overwriter-version</var></tag>
4220 <item>
4221 The <prgn>postrm</prgn> script is called after the package's
4222 files have been removed or replaced. The package
4223 whose <prgn>postrm</prgn> is being called may have
4224 previously been deconfigured and only be "Unpacked", at which
4225 point subsequent package changes do not consider its
4226 dependencies. Therefore, all <prgn>postrm</prgn> actions
4227 may only rely on essential packages and must gracefully skip
4228 any actions that require the package's dependencies if those
4229 dependencies are unavailable.<footnote>
4230 This is often done by checking whether the command or
4231 facility the <prgn>postrm</prgn> intends to call is
4232 available before calling it. For example:
4233 <example>
4234 if [ "$1" = purge ] && [ -e /usr/share/debconf/confmodule ]; then
4235 . /usr/share/debconf/confmodule
4236 db_purge
4238 </example>
4239 in <prgn>postrm</prgn> purges the <prgn>debconf</prgn>
4240 configuration for the package
4241 if <package>debconf</package> is installed.
4242 </footnote>
4243 </item>
4245 <tag><var>new-postrm</var> <tt>failed-upgrade</tt>
4246 <var>old-version</var></tag>
4247 <item>
4248 Called when the old <tt>postrm upgrade</tt> action fails.
4249 The new package will be unpacked, but only essential
4250 packages and pre-dependencies can be relied on.
4251 Pre-dependencies will either be configured or will be
4252 "Unpacked" or "Half-Configured" but previously had been
4253 configured and was never removed.
4254 </item>
4256 <tag><var>new-postrm</var> <tt>abort-install</tt></tag>
4257 <tag><var>new-postrm</var> <tt>abort-install</tt>
4258 <var>old-version</var></tag>
4259 <tag><var>new-postrm</var> <tt>abort-upgrade</tt>
4260 <var>old-version</var></tag>
4261 <item>
4262 Called before unpacking the new package as part of the
4263 error handling of <prgn>preinst</prgn> failures. May assume
4264 the same state as <prgn>preinst</prgn> can assume.
4265 </item>
4266 </taglist>
4267 </p>
4268 </sect>
4270 <sect id="unpackphase">
4271 <heading>Details of unpack phase of installation or upgrade</heading>
4274 The procedure on installation/upgrade/overwrite/disappear
4275 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
4276 stage of <tt>dpkg --install</tt>) is as follows. In each
4277 case, if a major error occurs (unless listed below) the
4278 actions are, in general, run backwards - this means that the
4279 maintainer scripts are run with different arguments in
4280 reverse order. These are the "error unwind" calls listed
4281 below.
4283 <enumlist>
4284 <item>
4285 <enumlist>
4286 <item>
4287 If a version of the package is already "Installed", call
4288 <example compact="compact">
4289 <var>old-prerm</var> upgrade <var>new-version</var>
4290 </example>
4291 </item>
4292 <item>
4293 If the script runs but exits with a non-zero
4294 exit status, <prgn>dpkg</prgn> will attempt:
4295 <example compact="compact">
4296 <var>new-prerm</var> failed-upgrade <var>old-version</var>
4297 </example>
4298 If this works, the upgrade continues. If this
4299 does not work, the error unwind:
4300 <example compact="compact">
4301 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4302 </example>
4303 If this works, then the old-version is
4304 "Installed", if not, the old version is in a
4305 "Half-Configured" state.
4306 </item>
4307 </enumlist>
4308 </item>
4310 <item>
4311 If a "conflicting" package is being removed at the same time,
4312 or if any package will be broken (due to <tt>Breaks</tt>):
4313 <enumlist>
4314 <item>
4315 If <tt>--auto-deconfigure</tt> is
4316 specified, call, for each package to be deconfigured
4317 due to <tt>Breaks</tt>:
4318 <example compact="compact">
4319 <var>deconfigured's-prerm</var> deconfigure \
4320 in-favour <var>package-being-installed</var> <var>version</var>
4321 </example>
4322 Error unwind:
4323 <example compact="compact">
4324 <var>deconfigured's-postinst</var> abort-deconfigure \
4325 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
4326 </example>
4327 The deconfigured packages are marked as
4328 requiring configuration, so that if
4329 <tt>--install</tt> is used they will be
4330 configured again if possible.
4331 </item>
4332 <item>
4333 If any packages depended on a conflicting
4334 package being removed and <tt>--auto-deconfigure</tt> is
4335 specified, call, for each such package:
4336 <example compact="compact">
4337 <var>deconfigured's-prerm</var> deconfigure \
4338 in-favour <var>package-being-installed</var> <var>version</var> \
4339 removing <var>conflicting-package</var> <var>version</var>
4340 </example>
4341 Error unwind:
4342 <example compact="compact">
4343 <var>deconfigured's-postinst</var> abort-deconfigure \
4344 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
4345 removing <var>conflicting-package</var> <var>version</var>
4346 </example>
4347 The deconfigured packages are marked as
4348 requiring configuration, so that if
4349 <tt>--install</tt> is used they will be
4350 configured again if possible.
4351 </item>
4352 <item>
4353 To prepare for removal of each conflicting package, call:
4354 <example compact="compact">
4355 <var>conflictor's-prerm</var> remove \
4356 in-favour <var>package</var> <var>new-version</var>
4357 </example>
4358 Error unwind:
4359 <example compact="compact">
4360 <var>conflictor's-postinst</var> abort-remove \
4361 in-favour <var>package</var> <var>new-version</var>
4362 </example>
4363 </item>
4364 </enumlist>
4365 </item>
4367 <item>
4368 <enumlist>
4369 <item>
4370 If the package is being upgraded, call:
4371 <example compact="compact">
4372 <var>new-preinst</var> upgrade <var>old-version</var>
4373 </example>
4374 If this fails, we call:
4375 <example>
4376 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4377 </example>
4378 <enumlist>
4379 <item>
4381 If that works, then
4382 <example>
4383 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4384 </example>
4385 is called. If this works, then the old version
4386 is in an "Installed" state, or else it is left
4387 in an "Unpacked" state.
4388 </p>
4389 </item>
4390 <item>
4392 If it fails, then the old version is left
4393 in an "Half-Installed" state.
4394 </p>
4395 </item>
4396 </enumlist>
4398 </item>
4399 <item>
4400 Otherwise, if the package had some configuration
4401 files from a previous version installed (i.e., it
4402 is in the "Config-Files" state):
4403 <example compact="compact">
4404 <var>new-preinst</var> install <var>old-version</var>
4405 </example>
4406 Error unwind:
4407 <example>
4408 <var>new-postrm</var> abort-install <var>old-version</var>
4409 </example>
4410 If this fails, the package is left in a
4411 "Half-Installed" state, which requires a
4412 reinstall. If it works, the packages is left in
4413 a "Config-Files" state.
4414 </item>
4415 <item>
4416 Otherwise (i.e., the package was completely purged):
4417 <example compact="compact">
4418 <var>new-preinst</var> install
4419 </example>
4420 Error unwind:
4421 <example compact="compact">
4422 <var>new-postrm</var> abort-install
4423 </example>
4424 If the error-unwind fails, the package is in a
4425 "Half-Installed" phase, and requires a
4426 reinstall. If the error unwind works, the
4427 package is in the "Not-Installed" state.
4428 </item>
4429 </enumlist>
4430 </item>
4432 <item>
4434 The new package's files are unpacked, overwriting any
4435 that may be on the system already, for example any
4436 from the old version of the same package or from
4437 another package. Backups of the old files are kept
4438 temporarily, and if anything goes wrong the package
4439 management system will attempt to put them back as
4440 part of the error unwind.
4441 </p>
4444 It is an error for a package to contain files which
4445 are on the system in another package, unless
4446 <tt>Replaces</tt> is used (see <ref id="replaces">).
4447 <!--
4448 The following paragraph is not currently the case:
4449 Currently the <tt>- - force-overwrite</tt> flag is
4450 enabled, downgrading it to a warning, but this may not
4451 always be the case.
4453 </p>
4456 It is a more serious error for a package to contain a
4457 plain file or other kind of non-directory where another
4458 package has a directory (again, unless
4459 <tt>Replaces</tt> is used). This error can be
4460 overridden if desired using
4461 <tt>--force-overwrite-dir</tt>, but this is not
4462 advisable.
4463 </p>
4466 Packages which overwrite each other's files produce
4467 behavior which, though deterministic, is hard for the
4468 system administrator to understand. It can easily
4469 lead to "missing" programs if, for example, a package
4470 is unpacked which overwrites a file from another
4471 package, and is then removed again.<footnote>
4472 Part of the problem is due to what is arguably a
4473 bug in <prgn>dpkg</prgn>.
4474 </footnote>
4475 </p>
4478 A directory will never be replaced by a symbolic link
4479 to a directory or vice versa; instead, the existing
4480 state (symlink or not) will be left alone and
4481 <prgn>dpkg</prgn> will follow the symlink if there is
4482 one.
4483 </p>
4484 </item>
4486 <item>
4488 <enumlist>
4489 <item>
4490 If the package is being upgraded, call
4491 <example compact="compact">
4492 <var>old-postrm</var> upgrade <var>new-version</var>
4493 </example>
4494 </item>
4495 <item>
4496 If this fails, <prgn>dpkg</prgn> will attempt:
4497 <example compact="compact">
4498 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4499 </example>
4500 If this works, installation continues. If not,
4501 Error unwind:
4502 <example compact="compact">
4503 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4504 </example>
4505 If this fails, the old version is left in a
4506 "Half-Installed" state. If it works, dpkg now
4507 calls:
4508 <example compact="compact">
4509 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4510 </example>
4511 If this fails, the old version is left in a
4512 "Half-Installed" state. If it works, dpkg now
4513 calls:
4514 <example compact="compact">
4515 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4516 </example>
4517 If this fails, the old version is in an
4518 "Unpacked" state.
4519 </item>
4520 </enumlist>
4521 </p>
4524 This is the point of no return - if
4525 <prgn>dpkg</prgn> gets this far, it won't back off
4526 past this point if an error occurs. This will
4527 leave the package in a fairly bad state, which
4528 will require a successful re-installation to clear
4529 up, but it's when <prgn>dpkg</prgn> starts doing
4530 things that are irreversible.
4531 </p>
4532 </item>
4534 <item>
4535 Any files which were in the old version of the package
4536 but not in the new are removed.
4537 </item>
4539 <item>
4540 The new file list replaces the old.
4541 </item>
4543 <item>
4544 The new maintainer scripts replace the old.
4545 </item>
4547 <item>
4548 Any packages all of whose files have been overwritten
4549 during the installation, and which aren't required for
4550 dependencies, are considered to have been removed.
4551 For each such package
4552 <enumlist>
4553 <item>
4554 <prgn>dpkg</prgn> calls:
4555 <example compact="compact">
4556 <var>disappearer's-postrm</var> disappear \
4557 <var>overwriter</var> <var>overwriter-version</var>
4558 </example>
4559 </item>
4560 <item>
4561 The package's maintainer scripts are removed.
4562 </item>
4563 <item>
4564 It is noted in the status database as being in a
4565 sane state, namely "Not-Installed" (any conffiles
4566 it may have are ignored, rather than being
4567 removed by <prgn>dpkg</prgn>). Note that
4568 disappearing packages do not have their prerm
4569 called, because <prgn>dpkg</prgn> doesn't know
4570 in advance that the package is going to
4571 vanish.
4572 </item>
4573 </enumlist>
4574 </item>
4576 <item>
4577 Any files in the package we're unpacking that are also
4578 listed in the file lists of other packages are removed
4579 from those lists. (This will lobotomize the file list
4580 of the "conflicting" package if there is one.)
4581 </item>
4583 <item>
4584 The backup files made during installation, above, are
4585 deleted.
4586 </item>
4588 <item>
4590 The new package's status is now sane, and recorded as
4591 "Unpacked".
4592 </p>
4595 Here is another point of no return - if the
4596 conflicting package's removal fails we do not unwind
4597 the rest of the installation; the conflicting package
4598 is left in a half-removed limbo.
4599 </p>
4600 </item>
4602 <item>
4603 If there was a conflicting package we go and do the
4604 removal actions (described below), starting with the
4605 removal of the conflicting package's files (any that
4606 are also in the package being unpacked have already
4607 been removed from the conflicting package's file list,
4608 and so do not get removed now).
4609 </item>
4610 </enumlist>
4611 </p>
4612 </sect>
4614 <sect id="configdetails"><heading>Details of configuration</heading>
4617 When we configure a package (this happens with <tt>dpkg
4618 --install</tt> and <tt>dpkg --configure</tt>), we first
4619 update any <tt>conffile</tt>s and then call:
4620 <example compact="compact">
4621 <var>postinst</var> configure <var>most-recently-configured-version</var>
4622 </example>
4623 </p>
4626 No attempt is made to unwind after errors during
4627 configuration. If the configuration fails, the package is in
4628 a "Half-Configured" state, and an error message is generated.
4629 </p>
4632 If there is no most recently configured version
4633 <prgn>dpkg</prgn> will pass a null argument.
4634 <footnote>
4636 Historical note: Truly ancient (pre-1997) versions of
4637 <prgn>dpkg</prgn> passed <tt>&lt;unknown&gt;</tt>
4638 (including the angle brackets) in this case. Even older
4639 ones did not pass a second argument at all, under any
4640 circumstance. Note that upgrades using such an old dpkg
4641 version are unlikely to work for other reasons, even if
4642 this old argument behavior is handled by your postinst script.
4643 </p>
4644 </footnote>
4645 </p>
4646 </sect>
4648 <sect id="removedetails"><heading>Details of removal and/or
4649 configuration purging</heading>
4652 <enumlist>
4653 <item>
4655 <example compact="compact">
4656 <var>prerm</var> remove
4657 </example>
4658 </p>
4660 If prerm fails during replacement due to conflict
4661 <example>
4662 <var>conflictor's-postinst</var> abort-remove \
4663 in-favour <var>package</var> <var>new-version</var>
4664 </example>
4665 Or else we call:
4666 <example>
4667 <var>postinst</var> abort-remove
4668 </example>
4669 </p>
4671 If this fails, the package is in a "Half-Configured"
4672 state, or else it remains "Installed".
4673 </p>
4674 </item>
4675 <item>
4676 The package's files are removed (except <tt>conffile</tt>s).
4677 </item>
4678 <item>
4679 <example compact="compact">
4680 <var>postrm</var> remove
4681 </example>
4684 If it fails, there's no error unwind, and the package is in
4685 an "Half-Installed" state.
4686 </p>
4687 </item>
4688 <item>
4690 All the maintainer scripts except the <prgn>postrm</prgn>
4691 are removed.
4692 </p>
4695 If we aren't purging the package we stop here. Note
4696 that packages which have no <prgn>postrm</prgn> and no
4697 <tt>conffile</tt>s are automatically purged when
4698 removed, as there is no difference except for the
4699 <prgn>dpkg</prgn> status.
4700 </p>
4701 </item>
4702 <item>
4703 The <tt>conffile</tt>s and any backup files
4704 (<tt>~</tt>-files, <tt>#*#</tt> files,
4705 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4706 are removed.
4707 </item>
4708 <item>
4710 <example compact="compact">
4711 <var>postrm</var> purge
4712 </example>
4713 </p>
4715 If this fails, the package remains in a "Config-Files"
4716 state.
4717 </p>
4718 </item>
4719 <item>
4720 The package's file list is removed.
4721 </item>
4722 </enumlist>
4724 </p>
4725 </sect>
4726 </chapt>
4729 <chapt id="relationships">
4730 <heading>Declaring relationships between packages</heading>
4732 <sect id="depsyntax">
4733 <heading>Syntax of relationship fields</heading>
4736 These fields all have a uniform syntax. They are a list of
4737 package names separated by commas.
4738 </p>
4741 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4742 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4743 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4744 control fields of the package, which declare
4745 dependencies on other packages, the package names listed may
4746 also include lists of alternative package names, separated
4747 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4748 that part of the dependency can be satisfied by any one of
4749 the alternative packages.
4750 </p>
4753 All of the fields except for <tt>Provides</tt> may restrict
4754 their applicability to particular versions of each named
4755 package. This is done in parentheses after each individual
4756 package name; the parentheses should contain a relation from
4757 the list below followed by a version number, in the format
4758 described in <ref id="f-Version">.
4759 </p>
4762 The relations allowed are <tt>&lt;&lt;</tt>, <tt>&lt;=</tt>,
4763 <tt>=</tt>, <tt>&gt;=</tt> and <tt>&gt;&gt;</tt> for strictly
4764 earlier, earlier or equal, exactly equal, later or equal and
4765 strictly later, respectively. The deprecated
4766 forms <tt>&lt;</tt> and <tt>&gt;</tt> were confusingly used to
4767 mean earlier/later or equal, rather than strictly earlier/later,
4768 and must not appear in new packages (though <prgn>dpkg</prgn>
4769 still supports them with a warning).
4770 </p>
4773 Whitespace may appear at any point in the version
4774 specification subject to the rules in <ref
4775 id="controlsyntax">, and must appear where it's necessary to
4776 disambiguate; it is not otherwise significant. All of the
4777 relationship fields can only be folded in source package control files. For
4778 consistency and in case of future changes to
4779 <prgn>dpkg</prgn> it is recommended that a single space be
4780 used after a version relationship and before a version
4781 number; it is also conventional to put a single space after
4782 each comma, on either side of each vertical bar, and before
4783 each open parenthesis. When opening a continuation line in a relationship field, it
4784 is conventional to do so after a comma and before the space
4785 following that comma.
4786 </p>
4789 For example, a list of dependencies might appear as:
4790 <example compact="compact">
4791 Package: mutt
4792 Version: 1.3.17-1
4793 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4794 </example>
4795 </p>
4798 Relationships may be restricted to a certain set of
4799 architectures. This is indicated in brackets after each
4800 individual package name and the optional version specification.
4801 The brackets enclose a non-empty list of Debian architecture names
4802 in the format described in <ref id="arch-spec">,
4803 separated by whitespace. Exclamation marks may be prepended to
4804 each of the names. (It is not permitted for some names to be
4805 prepended with exclamation marks while others aren't.)
4806 </p>
4809 For build relationship fields
4810 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4811 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4812 the current Debian host architecture is not in this list and
4813 there are no exclamation marks in the list, or it is in the list
4814 with a prepended exclamation mark, the package name and the
4815 associated version specification are ignored completely for the
4816 purposes of defining the relationships.
4817 </p>
4820 For example:
4821 <example compact="compact">
4822 Source: glibc
4823 Build-Depends-Indep: texinfo
4824 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4825 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4826 </example>
4827 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4828 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4829 <tt>gnumach-dev</tt> only on hurd-i386.
4830 </p>
4833 For binary relationship fields and the <tt>Built-Using</tt>
4834 field, the architecture restriction
4835 syntax is only supported in the source package control
4836 file <file>debian/control</file>. When the corresponding binary
4837 package control file is generated, the relationship will either
4838 be omitted or included without the architecture restriction
4839 based on the architecture of the binary package. This means
4840 that architecture restrictions must not be used in binary
4841 relationship fields for architecture-independent packages
4842 (<tt>Architecture: all</tt>).
4843 </p>
4846 For example:
4847 <example compact="compact">
4848 Depends: foo [i386], bar [amd64]
4849 </example>
4850 becomes <tt>Depends: foo</tt> when the package is built on
4851 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4852 package is built on the <tt>amd64</tt> architecture, and omitted
4853 entirely in binary packages built on all other architectures.
4854 </p>
4857 If the architecture-restricted dependency is part of a set of
4858 alternatives using <tt>|</tt>, that alternative is ignored
4859 completely on architectures that do not match the restriction.
4860 For example:
4861 <example compact="compact">
4862 Build-Depends: foo [!i386] | bar [!amd64]
4863 </example>
4864 is equivalent to <tt>bar</tt> on the i386 architecture, to
4865 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4866 bar</tt> on all other architectures.
4867 </p>
4870 Relationships may also be restricted to a certain set of
4871 architectures using architecture wildcards in the format
4872 described in <ref id="arch-wildcard-spec">. The syntax for
4873 declaring such restrictions is the same as declaring
4874 restrictions using a certain set of architectures without
4875 architecture wildcards. For example:
4876 <example compact="compact">
4877 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4878 </example>
4879 is equivalent to <tt>foo</tt> on architectures using the Linux
4880 kernel and any cpu, <tt>bar</tt> on architectures using any
4881 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4882 using a kernel other than Linux.
4883 </p>
4886 Note that the binary package relationship fields such as
4887 <tt>Depends</tt> appear in one of the binary package
4888 sections of the control file, whereas the build-time
4889 relationships such as <tt>Build-Depends</tt> appear in the
4890 source package section of the control file (which is the
4891 first section).
4892 </p>
4893 </sect>
4895 <sect id="binarydeps">
4896 <heading>Binary Dependencies - <tt>Depends</tt>,
4897 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4898 <tt>Pre-Depends</tt>
4899 </heading>
4902 Packages can declare in their control file that they have
4903 certain relationships to other packages - for example, that
4904 they may not be installed at the same time as certain other
4905 packages, and/or that they depend on the presence of others.
4906 </p>
4909 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4910 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4911 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4912 <tt>Breaks</tt> is described in <ref id="breaks">, and
4913 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4914 rest are described below.
4915 </p>
4918 These seven fields are used to declare a dependency
4919 relationship by one package on another. Except for
4920 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4921 depending (binary) package's control file.
4922 (<tt>Enhances</tt> appears in the recommending package's
4923 control file, and <tt>Breaks</tt> appears in the version of
4924 depended-on package which causes the named package to
4925 break).
4926 </p>
4929 A <tt>Depends</tt> field takes effect <em>only</em> when a
4930 package is to be configured. It does not prevent a package
4931 being on the system in an unconfigured state while its
4932 dependencies are unsatisfied, and it is possible to replace
4933 a package whose dependencies are satisfied and which is
4934 properly installed with a different version whose
4935 dependencies are not and cannot be satisfied; when this is
4936 done the depending package will be left unconfigured (since
4937 attempts to configure it will give errors) and will not
4938 function properly. If it is necessary, a
4939 <tt>Pre-Depends</tt> field can be used, which has a partial
4940 effect even when a package is being unpacked, as explained
4941 in detail below. (The other three dependency fields,
4942 <tt>Recommends</tt>, <tt>Suggests</tt> and
4943 <tt>Enhances</tt>, are only used by the various front-ends
4944 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4945 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4946 </p>
4949 Since <tt>Depends</tt> only places requirements on the order in
4950 which packages are configured, packages in an installation run
4951 are usually all unpacked first and all configured later.
4952 <footnote>
4953 This approach makes dependency resolution easier. If two
4954 packages A and B are being upgraded, the installed package A
4955 depends on exactly the installed package B, and the new
4956 package A depends on exactly the new package B (a common
4957 situation when upgrading shared libraries and their
4958 corresponding development packages), satisfying the
4959 dependencies at every stage of the upgrade would be
4960 impossible. This relaxed restriction means that both new
4961 packages can be unpacked together and then configured in their
4962 dependency order.
4963 </footnote>
4964 </p>
4967 If there is a circular dependency among packages being installed
4968 or removed, installation or removal order honoring the
4969 dependency order is impossible, requiring the dependency loop be
4970 broken at some point and the dependency requirements violated
4971 for at least one package. Packages involved in circular
4972 dependencies may not be able to rely on their dependencies being
4973 configured before they themselves are configured, depending on
4974 which side of the break of the circular dependency loop they
4975 happen to be on. If one of the packages in the loop has
4976 no <prgn>postinst</prgn> script, then the cycle will be broken
4977 at that package; this ensures that all <prgn>postinst</prgn>
4978 scripts are run with their dependencies properly configured if
4979 this is possible. Otherwise the breaking point is arbitrary.
4980 Packages should therefore avoid circular dependencies where
4981 possible, particularly if they have <prgn>postinst</prgn>
4982 scripts.
4983 </p>
4986 The meaning of the five dependency fields is as follows:
4987 <taglist>
4988 <tag><tt>Depends</tt></tag>
4989 <item>
4991 This declares an absolute dependency. A package will
4992 not be configured unless all of the packages listed in
4993 its <tt>Depends</tt> field have been correctly
4994 configured (unless there is a circular dependency as
4995 described above).
4996 </p>
4999 The <tt>Depends</tt> field should be used if the
5000 depended-on package is required for the depending
5001 package to provide a significant amount of
5002 functionality.
5003 </p>
5006 The <tt>Depends</tt> field should also be used if the
5007 <prgn>postinst</prgn> or <prgn>prerm</prgn> scripts
5008 require the depended-on package to be unpacked or
5009 configured in order to run. In the case of <tt>postinst
5010 configure</tt>, the depended-on packages will be unpacked
5011 and configured first. (If both packages are involved in a
5012 dependency loop, this might not work as expected; see the
5013 explanation a few paragraphs back.) In the case
5014 of <prgn>prerm</prgn> or other <prgn>postinst</prgn>
5015 actions, the package dependencies will normally be at
5016 least unpacked, but they may be only "Half-Installed" if a
5017 previous upgrade of the dependency failed.
5018 </p>
5021 Finally, the <tt>Depends</tt> field should be used if the
5022 depended-on package is needed by the <prgn>postrm</prgn>
5023 script to fully clean up after the package removal. There
5024 is no guarantee that package dependencies will be
5025 available when <prgn>postrm</prgn> is run, but the
5026 depended-on package is more likely to be available if the
5027 package declares a dependency (particularly in the case
5028 of <tt>postrm remove</tt>). The <prgn>postrm</prgn>
5029 script must gracefully skip actions that require a
5030 dependency if that dependency isn't available.
5031 </p>
5032 </item>
5034 <tag><tt>Recommends</tt></tag>
5035 <item>
5037 This declares a strong, but not absolute, dependency.
5038 </p>
5041 The <tt>Recommends</tt> field should list packages
5042 that would be found together with this one in all but
5043 unusual installations.
5044 </p>
5045 </item>
5047 <tag><tt>Suggests</tt></tag>
5048 <item>
5049 This is used to declare that one package may be more
5050 useful with one or more others. Using this field
5051 tells the packaging system and the user that the
5052 listed packages are related to this one and can
5053 perhaps enhance its usefulness, but that installing
5054 this one without them is perfectly reasonable.
5055 </item>
5057 <tag><tt>Enhances</tt></tag>
5058 <item>
5059 This field is similar to Suggests but works in the
5060 opposite direction. It is used to declare that a
5061 package can enhance the functionality of another
5062 package.
5063 </item>
5065 <tag><tt>Pre-Depends</tt></tag>
5066 <item>
5068 This field is like <tt>Depends</tt>, except that it
5069 also forces <prgn>dpkg</prgn> to complete installation
5070 of the packages named before even starting the
5071 installation of the package which declares the
5072 pre-dependency, as follows:
5073 </p>
5076 When a package declaring a pre-dependency is about to
5077 be <em>unpacked</em> the pre-dependency can be
5078 satisfied if the depended-on package is either fully
5079 configured, <em>or even if</em> the depended-on
5080 package(s) are only in the "Unpacked" or the "Half-Configured"
5081 state, provided that they have been configured
5082 correctly at some point in the past (and not removed
5083 or partially removed since). In this case, both the
5084 previously-configured and currently "Unpacked" or
5085 "Half-Configured" versions must satisfy any version
5086 clause in the <tt>Pre-Depends</tt> field.
5087 </p>
5090 When the package declaring a pre-dependency is about to
5091 be <em>configured</em>, the pre-dependency will be treated
5092 as a normal <tt>Depends</tt>. It will be considered
5093 satisfied only if the depended-on package has been
5094 correctly configured. However, unlike
5095 with <tt>Depends</tt>, <tt>Pre-Depends</tt> does not
5096 permit circular dependencies to be broken. If a circular
5097 dependency is encountered while attempting to honor
5098 <tt>Pre-Depends</tt>, the installation will be aborted.
5099 </p>
5102 <tt>Pre-Depends</tt> are also required if the
5103 <prgn>preinst</prgn> script depends on the named package.
5104 It is best to avoid this situation if possible.
5105 </p>
5108 <tt>Pre-Depends</tt> should be used sparingly,
5109 preferably only by packages whose premature upgrade or
5110 installation would hamper the ability of the system to
5111 continue with any upgrade that might be in progress.
5112 </p>
5115 You should not specify a <tt>Pre-Depends</tt> entry for a
5116 package before this has been discussed on the
5117 <tt>debian-devel</tt> mailing list and a consensus about
5118 doing that has been reached. See <ref id="dependencies">.
5119 </p>
5120 </item>
5121 </taglist>
5122 </p>
5125 When selecting which level of dependency to use you should
5126 consider how important the depended-on package is to the
5127 functionality of the one declaring the dependency. Some
5128 packages are composed of components of varying degrees of
5129 importance. Such a package should list using
5130 <tt>Depends</tt> the package(s) which are required by the
5131 more important components. The other components'
5132 requirements may be mentioned as Suggestions or
5133 Recommendations, as appropriate to the components' relative
5134 importance.
5135 </p>
5136 </sect>
5138 <sect id="breaks">
5139 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
5142 When one binary package declares that it breaks another,
5143 <prgn>dpkg</prgn> will refuse to allow the package which
5144 declares <tt>Breaks</tt> to be unpacked unless the broken
5145 package is deconfigured first, and it will refuse to
5146 allow the broken package to be reconfigured.
5147 </p>
5150 A package will not be regarded as causing breakage merely
5151 because its configuration files are still installed; it must
5152 be at least "Half-Installed".
5153 </p>
5156 A special exception is made for packages which declare that
5157 they break their own package name or a virtual package which
5158 they provide (see below): this does not count as a real
5159 breakage.
5160 </p>
5163 Normally a <tt>Breaks</tt> entry will have an "earlier than"
5164 version clause; such a <tt>Breaks</tt> is introduced in the
5165 version of an (implicit or explicit) dependency which violates
5166 an assumption or reveals a bug in earlier versions of the broken
5167 package, or which takes over a file from earlier versions of the
5168 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
5169 will inform higher-level package management tools that the
5170 broken package must be upgraded before the new one.
5171 </p>
5174 If the breaking package also overwrites some files from the
5175 older package, it should use <tt>Replaces</tt> to ensure this
5176 goes smoothly. See <ref id="replaces"> for a full discussion
5177 of taking over files from other packages, including how to
5178 use <tt>Breaks</tt> in those cases.
5179 </p>
5182 Many of the cases where <tt>Breaks</tt> should be used were
5183 previously handled with <tt>Conflicts</tt>
5184 because <tt>Breaks</tt> did not yet exist.
5185 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
5186 See <ref id="conflicts"> for more information about the
5187 differences.
5188 </p>
5189 </sect>
5191 <sect id="conflicts">
5192 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
5195 When one binary package declares a conflict with another using
5196 a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will refuse to
5197 allow them to be unpacked on the system at the same time. This
5198 is a stronger restriction than <tt>Breaks</tt>, which prevents
5199 the broken package from being configured while the breaking
5200 package is in the "Unpacked" state but allows both packages to
5201 be unpacked at the same time.
5202 </p>
5205 If one package is to be unpacked, the other must be removed
5206 first. If the package being unpacked is marked as replacing
5207 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
5208 normally be used in this case) the one on the system, or the one
5209 on the system is marked as deselected, or both packages are
5210 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
5211 automatically remove the package which is causing the conflict.
5212 Otherwise, it will halt the installation of the new package with
5213 an error. This mechanism is specifically designed to produce an
5214 error when the installed package is <tt>Essential</tt>, but the
5215 new package is not.
5216 </p>
5219 A package will not cause a conflict merely because its
5220 configuration files are still installed; it must be at least
5221 "Half-Installed".
5222 </p>
5225 A special exception is made for packages which declare a
5226 conflict with their own package name, or with a virtual
5227 package which they provide (see below): this does not
5228 prevent their installation, and allows a package to conflict
5229 with others providing a replacement for it. You use this
5230 feature when you want the package in question to be the only
5231 package providing some feature.
5232 </p>
5235 Normally, <tt>Breaks</tt> should be used instead
5236 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
5237 stronger restriction on the ordering of package installation or
5238 upgrade and can make it more difficult for the package manager
5239 to find a correct solution to an upgrade or installation
5240 problem. <tt>Breaks</tt> should be used
5241 <list>
5242 <item>when moving a file from one package to another (see
5243 <ref id="replaces">),</item>
5244 <item>when splitting a package (a special case of the previous
5245 one), or</item>
5246 <item>when the breaking package exposes a bug in or interacts
5247 badly with particular versions of the broken
5248 package.</item>
5249 </list>
5250 <tt>Conflicts</tt> should be used
5251 <list>
5252 <item>when two packages provide the same file and will
5253 continue to do so,</item>
5254 <item>in conjunction with <tt>Provides</tt> when only one
5255 package providing a given virtual facility may be unpacked
5256 at a time (see <ref id="virtual">),</item>
5257 <item>in other cases where one must prevent simultaneous
5258 installation of two packages for reasons that are ongoing
5259 (not fixed in a later version of one of the packages) or
5260 that must prevent both packages from being unpacked at the
5261 same time, not just configured.</item>
5262 </list>
5263 Be aware that adding <tt>Conflicts</tt> is normally not the best
5264 solution when two packages provide the same files. Depending on
5265 the reason for that conflict, using alternatives or renaming the
5266 files is often a better approach. See, for
5267 example, <ref id="binaries">.
5268 </p>
5271 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
5272 unless two packages cannot be installed at the same time or
5273 installing them both causes one of them to be broken or
5274 unusable. Having similar functionality or performing the same
5275 tasks as another package is not sufficient reason to
5276 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
5277 </p>
5280 A <tt>Conflicts</tt> entry may have an "earlier than" version
5281 clause if the reason for the conflict is corrected in a later
5282 version of one of the packages. However, normally the presence
5283 of an "earlier than" version clause is a sign
5284 that <tt>Breaks</tt> should have been used instead. An "earlier
5285 than" version clause in <tt>Conflicts</tt>
5286 prevents <prgn>dpkg</prgn> from upgrading or installing the
5287 package which declares such a conflict until the upgrade or
5288 removal of the conflicted-with package has been completed, which
5289 is a strong restriction.
5290 </p>
5291 </sect>
5293 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
5294 </heading>
5297 As well as the names of actual ("concrete") packages, the
5298 package relationship fields <tt>Depends</tt>,
5299 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
5300 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
5301 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5302 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
5303 may mention "virtual packages".
5304 </p>
5307 A <em>virtual package</em> is one which appears in the
5308 <tt>Provides</tt> control field of another package. The effect
5309 is as if the package(s) which provide a particular virtual
5310 package name had been listed by name everywhere the virtual
5311 package name appears. (See also <ref id="virtual_pkg">)
5312 </p>
5315 If there are both concrete and virtual packages of the same
5316 name, then the dependency may be satisfied (or the conflict
5317 caused) by either the concrete package with the name in
5318 question or any other concrete package which provides the
5319 virtual package with the name in question. This is so that,
5320 for example, supposing we have
5321 <example compact="compact">
5322 Package: foo
5323 Depends: bar
5324 </example> and someone else releases an enhanced version of
5325 the <tt>bar</tt> package they can say:
5326 <example compact="compact">
5327 Package: bar-plus
5328 Provides: bar
5329 </example>
5330 and the <tt>bar-plus</tt> package will now also satisfy the
5331 dependency for the <tt>foo</tt> package.
5332 </p>
5335 If a relationship field has a version number attached, only real
5336 packages will be considered to see whether the relationship is
5337 satisfied (or the prohibition violated, for a conflict or
5338 breakage). In other words, if a version number is specified,
5339 this is a request to ignore all <tt>Provides</tt> for that
5340 package name and consider only real packages. The package
5341 manager will assume that a package providing that virtual
5342 package is not of the "right" version. A <tt>Provides</tt>
5343 field may not contain version numbers, and the version number of
5344 the concrete package which provides a particular virtual package
5345 will not be considered when considering a dependency on or
5346 conflict with the virtual package name.<footnote>
5347 It is possible that a future release of <prgn>dpkg</prgn> may
5348 add the ability to specify a version number for each virtual
5349 package it provides. This feature is not yet present,
5350 however, and is expected to be used only infrequently.
5351 </footnote>
5352 </p>
5355 To specify which of a set of real packages should be the default
5356 to satisfy a particular dependency on a virtual package, list
5357 the real package as an alternative before the virtual one.
5358 </p>
5361 If the virtual package represents a facility that can only be
5362 provided by one real package at a time, such as
5363 the <package>mail-transport-agent</package> virtual package that
5364 requires installation of a binary that would conflict with all
5365 other providers of that virtual package (see
5366 <ref id="mail-transport-agents">), all packages providing that
5367 virtual package should also declare a conflict with it
5368 using <tt>Conflicts</tt>. This will ensure that at most one
5369 provider of that virtual package is unpacked or installed at a
5370 time.
5371 </p>
5372 </sect>
5374 <sect id="replaces"><heading>Overwriting files and replacing
5375 packages - <tt>Replaces</tt></heading>
5378 Packages can declare in their control file that they should
5379 overwrite files in certain other packages, or completely replace
5380 other packages. The <tt>Replaces</tt> control field has these
5381 two distinct purposes.
5382 </p>
5384 <sect1><heading>Overwriting files in other packages</heading>
5387 It is usually an error for a package to contain files which
5388 are on the system in another package. However, if the
5389 overwriting package declares that it <tt>Replaces</tt> the one
5390 containing the file being overwritten, then <prgn>dpkg</prgn>
5391 will replace the file from the old package with that from the
5392 new. The file will no longer be listed as "owned" by the old
5393 package and will be taken over by the new package.
5394 Normally, <tt>Breaks</tt> should be used in conjunction
5395 with <tt>Replaces</tt>.<footnote>
5396 To see why <tt>Breaks</tt> is normally needed in addition
5397 to <tt>Replaces</tt>, consider the case of a file in the
5398 package <package>foo</package> being taken over by the
5399 package <package>foo-data</package>.
5400 <tt>Replaces</tt> will allow <package>foo-data</package> to
5401 be installed and take over that file. However,
5402 without <tt>Breaks</tt>, nothing
5403 requires <package>foo</package> to be upgraded to a newer
5404 version that knows it does not include that file and instead
5405 depends on <package>foo-data</package>. Nothing would
5406 prevent the new <package>foo-data</package> package from
5407 being installed and then removed, removing the file that it
5408 took over from <package>foo</package>. After that
5409 operation, the package manager would think the system was in
5410 a consistent state, but the <package>foo</package> package
5411 would be missing one of its files.
5412 </footnote>
5413 </p>
5416 For example, if a package <package>foo</package> is split
5417 into <package>foo</package> and <package>foo-data</package>
5418 starting at version 1.2-3, <package>foo-data</package> would
5419 have the fields
5420 <example compact="compact">
5421 Replaces: foo (&lt;&lt; 1.2-3)
5422 Breaks: foo (&lt;&lt; 1.2-3)
5423 </example>
5424 in its control file. The new version of the
5425 package <package>foo</package> would normally have the field
5426 <example compact="compact">
5427 Depends: foo-data (&gt;= 1.2-3)
5428 </example>
5429 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5430 the files moved into <package>foo-data</package> are not
5431 required for normal operation).
5432 </p>
5435 If a package is completely replaced in this way, so that
5436 <prgn>dpkg</prgn> does not know of any files it still
5437 contains, it is considered to have "disappeared". It will
5438 be marked as not wanted on the system (selected for
5439 removal) and "Not-Installed". Any <tt>conffile</tt>s
5440 details noted for the package will be ignored, as they
5441 will have been taken over by the overwriting package. The
5442 package's <prgn>postrm</prgn> script will be run with a
5443 special argument to allow the package to do any final
5444 cleanup required. See <ref id="mscriptsinstact">.
5445 <footnote>
5446 Replaces is a one way relationship. You have to install
5447 the replacing package after the replaced package.
5448 </footnote>
5449 </p>
5452 For this usage of <tt>Replaces</tt>, virtual packages (see
5453 <ref id="virtual">) are not considered when looking at a
5454 <tt>Replaces</tt> field. The packages declared as being
5455 replaced must be mentioned by their real names.
5456 </p>
5459 This usage of <tt>Replaces</tt> only takes effect when both
5460 packages are at least partially on the system at once. It is
5461 not relevant if the packages conflict unless the conflict has
5462 been overridden.
5463 </p>
5464 </sect1>
5466 <sect1><heading>Replacing whole packages, forcing their
5467 removal</heading>
5470 Second, <tt>Replaces</tt> allows the packaging system to
5471 resolve which package should be removed when there is a
5472 conflict (see <ref id="conflicts">). This usage only takes
5473 effect when the two packages <em>do</em> conflict, so that the
5474 two usages of this field do not interfere with each other.
5475 </p>
5478 In this situation, the package declared as being replaced
5479 can be a virtual package, so for example, all mail
5480 transport agents (MTAs) would have the following fields in
5481 their control files:
5482 <example compact="compact">
5483 Provides: mail-transport-agent
5484 Conflicts: mail-transport-agent
5485 Replaces: mail-transport-agent
5486 </example>
5487 ensuring that only one MTA can be unpacked at any one
5488 time. See <ref id="virtual"> for more information about this
5489 example.
5490 </sect1>
5491 </sect>
5493 <sect id="sourcebinarydeps">
5494 <heading>Relationships between source and binary packages -
5495 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5496 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5497 </heading>
5500 Source packages that require certain binary packages to be
5501 installed or absent at the time of building the package
5502 can declare relationships to those binary packages.
5503 </p>
5506 This is done using the <tt>Build-Depends</tt>,
5507 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5508 <tt>Build-Conflicts-Indep</tt> control fields.
5509 </p>
5512 Build-dependencies on "build-essential" binary packages can be
5513 omitted. Please see <ref id="pkg-relations"> for more information.
5514 </p>
5517 The dependencies and conflicts they define must be satisfied
5518 (as defined earlier for binary packages) in order to invoke
5519 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5521 There is no Build-Depends-Arch; this role is essentially
5522 met with Build-Depends. Anyone building the
5523 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5524 assumed to be building the whole package, and therefore
5525 installation of all build dependencies is required.
5526 </p>
5528 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5529 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5530 not yet know how to check for its existence, and
5531 <tt>binary-arch</tt>. The purpose of the original split
5532 between <tt>Build-Depends</tt> and
5533 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5534 wouldn't need to install extra packages needed only for the
5535 binary-indep targets. But without a build-arch/build-indep
5536 split, this didn't work, since most of the work is done in
5537 the build target, not in the binary target.
5538 </p>
5539 </footnote>
5540 <taglist>
5541 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5542 <tt>binary-arch</tt></tag>
5543 <item>
5544 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5545 fields must be satisfied when these targets are invoked.
5546 </item>
5547 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5548 and <tt>binary-indep</tt></tag>
5549 <item>
5550 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5551 <tt>Build-Depends-Indep</tt>, and
5552 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5553 these targets are invoked.
5554 </item>
5555 </taglist>
5556 </p>
5557 </sect>
5559 <sect id="built-using">
5560 <heading>Additional source packages used to build the binary
5561 - <tt>Built-Using</tt>
5562 </heading>
5565 Some binary packages incorporate parts of other packages when built
5566 but do not have to depend on those packages. Examples include
5567 linking with static libraries or incorporating source code from
5568 another package during the build. In this case, the source packages
5569 of those other packages are a required part of the complete source
5570 (the binary package is not reproducible without them).
5571 </p>
5574 A <tt>Built-Using</tt> field must list the corresponding source
5575 package for any such binary package incorporated during the build
5576 <footnote>
5577 <tt>Build-Depends</tt> in the source package is not adequate since
5578 it (rightfully) does not document the exact version used in the
5579 build.
5580 </footnote>,
5581 including an "exactly equal" ("=") version relation on the version
5582 that was used to build that binary package<footnote>
5583 The archive software might reject packages that refer to
5584 non-existent sources.
5585 </footnote>.
5586 </p>
5589 A package using the source code from the gcc-4.6-source
5590 binary package built from the gcc-4.6 source package would
5591 have this field in its control file:
5592 <example compact="compact">
5593 Built-Using: gcc-4.6 (= 4.6.0-11)
5594 </example>
5595 </p>
5598 A package including binaries from grub2 and loadlin would
5599 have this field in its control file:
5600 <example compact="compact">
5601 Built-Using: grub2 (= 1.99-9), loadlin (= 1.6e-1)
5602 </example>
5603 </p>
5604 </sect>
5605 </chapt>
5608 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5611 Packages containing shared libraries must be constructed with
5612 a little care to make sure that the shared library is always
5613 available. This is especially important for packages whose
5614 shared libraries are vitally important, such as the C library
5615 (currently <tt>libc6</tt>).
5616 </p>
5619 This section deals only with public shared libraries: shared
5620 libraries that are placed in directories searched by the dynamic
5621 linker by default or which are intended to be linked against
5622 normally and possibly used by other, independent packages. Shared
5623 libraries that are internal to a particular package or that are
5624 only loaded as dynamic modules are not covered by this section and
5625 are not subject to its requirements.
5626 </p>
5629 A shared library is identified by the <tt>SONAME</tt> attribute
5630 stored in its dynamic section. When a binary is linked against a
5631 shared library, the <tt>SONAME</tt> of the shared library is
5632 recorded in the binary's <tt>NEEDED</tt> section so that the
5633 dynamic linker knows that library must be loaded at runtime. The
5634 shared library file's full name (which usually contains additional
5635 version information not needed in the <tt>SONAME</tt>) is
5636 therefore normally not referenced directly. Instead, the shared
5637 library is loaded by its <tt>SONAME</tt>, which exists on the file
5638 system as a symlink pointing to the full name of the shared
5639 library. This symlink must be provided by the
5640 package. <ref id="sharedlibs-runtime"> describes how to do this.
5641 <footnote>
5642 This is a convention of shared library versioning, but not a
5643 requirement. Some libraries use the <tt>SONAME</tt> as the full
5644 library file name instead and therefore do not need a symlink.
5645 Most, however, encode additional information about
5646 backwards-compatible revisions as a minor version number in the
5647 file name. The <tt>SONAME</tt> itself only changes when
5648 binaries linked with the earlier version of the shared library
5649 may no longer work, but the filename may change with each
5650 release of the library. See <ref id="sharedlibs-runtime"> for
5651 more information.
5652 </footnote>
5653 </p>
5656 When linking a binary or another shared library against a shared
5657 library, the <tt>SONAME</tt> for that shared library is not yet
5658 known. Instead, the shared library is found by looking for a file
5659 matching the library name with <tt>.so</tt> appended. This file
5660 exists on the file system as a symlink pointing to the shared
5661 library.
5662 </p>
5665 Shared libraries are normally split into several binary packages.
5666 The <tt>SONAME</tt> symlink is installed by the runtime shared
5667 library package, and the bare <tt>.so</tt> symlink is installed in
5668 the development package since it's only used when linking binaries
5669 or shared libraries. However, there are some exceptions for
5670 unusual shared libraries or for shared libraries that are also
5671 loaded as dynamic modules by other programs.
5672 </p>
5675 This section is primarily concerned with how the separation of
5676 shared libraries into multiple packages should be done and how
5677 dependencies on and between shared library binary packages are
5678 managed in Debian. <ref id="libraries"> should be read in
5679 conjunction with this section and contains additional rules for
5680 the files contained in the shared library packages.
5681 </p>
5683 <sect id="sharedlibs-runtime">
5684 <heading>Run-time shared libraries</heading>
5687 The run-time shared library must be placed in a package
5688 whose name changes whenever the <tt>SONAME</tt> of the shared
5689 library changes. This allows several versions of the shared
5690 library to be installed at the same time, allowing installation
5691 of the new version of the shared library without immediately
5692 breaking binaries that depend on the old version. Normally, the
5693 run-time shared library and its <tt>SONAME</tt> symlink should
5694 be placed in a package named
5695 <package><var>libraryname</var><var>soversion</var></package>,
5696 where <var>soversion</var> is the version number in
5697 the <tt>SONAME</tt> of the shared library. Alternatively, if it
5698 would be confusing to directly append <var>soversion</var>
5699 to <var>libraryname</var> (if, for
5700 example, <var>libraryname</var> itself ends in a number), you
5701 should use
5702 <package><var>libraryname</var>-<var>soversion</var></package>
5703 instead.
5704 </p>
5707 To determine the <var>soversion</var>, look at
5708 the <tt>SONAME</tt> of the library, stored in the
5709 ELF <tt>SONAME</tt> attribute. It is usually of the
5710 form <tt><var>name</var>.so.<var>major-version</var></tt> (for
5711 example, <tt>libz.so.1</tt>). The version part is the part
5712 which comes after <tt>.so.</tt>, so in that example it
5713 is <tt>1</tt>. The soname may instead be of the
5714 form <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5715 as <tt>libdb-5.1.so</tt>, in which case the name would
5716 be <tt>libdb</tt> and the version would be <tt>5.1</tt>.
5717 </p>
5720 If you have several shared libraries built from the same source
5721 tree, you may lump them all together into a single shared
5722 library package provided that all of their <tt>SONAME</tt>s will
5723 always change together. Be aware that this is not normally the
5724 case, and if the <tt>SONAME</tt>s do not change together,
5725 upgrading such a merged shared library package will be
5726 unnecessarily difficult because of file conflicts with the old
5727 version of the package. When in doubt, always split shared
5728 library packages so that each binary package installs a single
5729 shared library.
5730 </p>
5733 Every time the shared library ABI changes in a way that may
5734 break binaries linked against older versions of the shared
5735 library, the <tt>SONAME</tt> of the library and the
5736 corresponding name for the binary package containing the runtime
5737 shared library should change. Normally, this means
5738 the <tt>SONAME</tt> should change any time an interface is
5739 removed from the shared library or the signature of an interface
5740 (the number of parameters or the types of parameters that it
5741 takes, for example) is changed. This practice is vital to
5742 allowing clean upgrades from older versions of the package and
5743 clean transitions between the old ABI and new ABI without having
5744 to upgrade every affected package simultaneously.
5745 </p>
5748 The <tt>SONAME</tt> and binary package name need not, and indeed
5749 normally should not, change if new interfaces are added but none
5750 are removed or changed, since this will not break binaries
5751 linked against the old shared library. Correct versioning of
5752 dependencies on the newer shared library by binaries that use
5753 the new interfaces is handled via
5754 the <qref id="sharedlibs-depends"><tt>symbols</tt>
5755 or <tt>shlibs</tt> system</qref>.
5756 </p>
5759 The package should install the shared libraries under
5760 their normal names. For example, the <package>libgdbm3</package>
5761 package should install <file>libgdbm.so.3.0.0</file> as
5762 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5763 renamed or re-linked by any <prgn>prerm</prgn> or
5764 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5765 of renaming things safely without affecting running programs,
5766 and attempts to interfere with this are likely to lead to
5767 problems.
5768 </p>
5771 Shared libraries should not be installed executable, since
5772 the dynamic linker does not require this and trying to
5773 execute a shared library usually results in a core dump.
5774 </p>
5777 The run-time library package should include the symbolic link for
5778 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5779 the shared libraries. For example,
5780 the <package>libgdbm3</package> package should include a symbolic
5781 link from <file>/usr/lib/libgdbm.so.3</file> to
5782 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5783 linker (for example <prgn>ld.so</prgn> or
5784 <prgn>ld-linux.so.*</prgn>) can find the library between the
5785 time that <prgn>dpkg</prgn> installs it and the time that
5786 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5787 script.<footnote>
5788 The package management system requires the library to be
5789 placed before the symbolic link pointing to it in the
5790 <file>.deb</file> file. This is so that when
5791 <prgn>dpkg</prgn> comes to install the symlink
5792 (overwriting the previous symlink pointing at an older
5793 version of the library), the new shared library is already
5794 in place. In the past, this was achieved by creating the
5795 library in the temporary packaging directory before
5796 creating the symlink. Unfortunately, this was not always
5797 effective, since the building of the tar file in the
5798 <file>.deb</file> depended on the behavior of the underlying
5799 file system. Some file systems (such as reiserfs) reorder
5800 the files so that the order of creation is forgotten.
5801 Since version 1.7.0, <prgn>dpkg</prgn>
5802 reorders the files itself as necessary when building a
5803 package. Thus it is no longer important to concern
5804 oneself with the order of file creation.
5805 </footnote>
5806 </p>
5808 <sect1 id="ldconfig">
5809 <heading><tt>ldconfig</tt></heading>
5812 Any package installing shared libraries in one of the default
5813 library directories of the dynamic linker (which are currently
5814 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5815 listed in <file>/etc/ld.so.conf</file><footnote>
5816 These are currently <file>/usr/local/lib</file> plus
5817 directories under <file>/lib</file> and <file>/usr/lib</file>
5818 matching the multiarch triplet for the system architecture.
5819 </footnote>
5820 must use <prgn>ldconfig</prgn> to update the shared library
5821 system.
5822 </p>
5825 The package maintainer scripts must only call
5826 <prgn>ldconfig</prgn> under these circumstances:
5827 <list compact="compact">
5828 <item>When the <prgn>postinst</prgn> script is run with a
5829 first argument of <tt>configure</tt>, the script must call
5830 <prgn>ldconfig</prgn>, and may optionally invoke
5831 <prgn>ldconfig</prgn> at other times.
5832 </item>
5833 <item>When the <prgn>postrm</prgn> script is run with a
5834 first argument of <tt>remove</tt>, the script should call
5835 <prgn>ldconfig</prgn>.
5836 </item>
5837 </list>
5838 <footnote>
5840 During install or upgrade, the preinst is called before
5841 the new files are unpacked, so calling "ldconfig" is
5842 pointless. The preinst of an existing package can also be
5843 called if an upgrade fails. However, this happens during
5844 the critical time when a shared libs may exist on-disk
5845 under a temporary name. Thus, it is dangerous and
5846 forbidden by current policy to call "ldconfig" at this
5847 time.
5848 </p>
5851 When a package is installed or upgraded, "postinst
5852 configure" runs after the new files are safely on-disk.
5853 Since it is perfectly safe to invoke ldconfig
5854 unconditionally in a postinst, it is OK for a package to
5855 simply put ldconfig in its postinst without checking the
5856 argument. The postinst can also be called to recover from
5857 a failed upgrade. This happens before any new files are
5858 unpacked, so there is no reason to call "ldconfig" at this
5859 point.
5860 </p>
5863 For a package that is being removed, prerm is
5864 called with all the files intact, so calling ldconfig is
5865 useless. The other calls to "prerm" happen in the case of
5866 upgrade at a time when all the files of the old package
5867 are on-disk, so again calling "ldconfig" is pointless.
5868 </p>
5871 postrm, on the other hand, is called with the "remove"
5872 argument just after the files are removed, so this is
5873 the proper time to call "ldconfig" to notify the system
5874 of the fact that the shared libraries from the package
5875 are removed. The postrm can be called at several other
5876 times. At the time of "postrm purge", "postrm
5877 abort-install", or "postrm abort-upgrade", calling
5878 "ldconfig" is useless because the shared lib files are
5879 not on-disk. However, when "postrm" is invoked with
5880 arguments "upgrade", "failed-upgrade", or "disappear", a
5881 shared lib may exist on-disk under a temporary filename.
5882 </p>
5883 </footnote>
5884 </p>
5885 </sect1>
5887 </sect>
5889 <sect id="sharedlibs-support-files">
5890 <heading>Shared library support files</heading>
5893 If your package contains files whose names do not change with
5894 each change in the library shared object version, you must not
5895 put them in the shared library package. Otherwise, several
5896 versions of the shared library cannot be installed at the same
5897 time without filename clashes, making upgrades and transitions
5898 unnecessarily difficult.
5899 </p>
5902 It is recommended that supporting files and run-time support
5903 programs that do not need to be invoked manually by users, but
5904 are nevertheless required for the package to function, be placed
5905 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5906 preferably under <file>/usr/lib/</file><var>package-name</var>.
5907 If the program or file is architecture independent, the
5908 recommendation is for it to be placed in a subdirectory of
5909 <file>/usr/share</file> instead, preferably under
5910 <file>/usr/share/</file><var>package-name</var>. Following the
5911 <var>package-name</var> naming convention ensures that the file
5912 names change when the shared object version changes.
5913 </p>
5916 Run-time support programs that use the shared library but are
5917 not required for the library to function or files used by the
5918 shared library that can be used by any version of the shared
5919 library package should instead be put in a separate package.
5920 This package might typically be named
5921 <package><var>libraryname</var>-tools</package>; note the
5922 absence of the <var>soversion</var> in the package name.
5923 </p>
5926 Files and support programs only useful when compiling software
5927 against the library should be included in the development
5928 package for the library.<footnote>
5929 For example, a <file><var>package-name</var>-config</file>
5930 script or <package>pkg-config</package> configuration files.
5931 </footnote>
5932 </p>
5933 </sect>
5935 <sect id="sharedlibs-static">
5936 <heading>Static libraries</heading>
5939 The static library (<file><var>libraryname.a</var></file>)
5940 is usually provided in addition to the shared version.
5941 It is placed into the development package (see below).
5942 </p>
5945 In some cases, it is acceptable for a library to be
5946 available in static form only; these cases include:
5947 <list>
5948 <item>libraries for languages whose shared library support
5949 is immature or unstable</item>
5950 <item>libraries whose interfaces are in flux or under
5951 development (commonly the case when the library's
5952 major version number is zero, or where the ABI breaks
5953 across patchlevels)</item>
5954 <item>libraries which are explicitly intended to be
5955 available only in static form by their upstream
5956 author(s)</item>
5957 </list>
5958 </p>
5960 <sect id="sharedlibs-dev">
5961 <heading>Development files</heading>
5964 If there are development files associated with a shared library,
5965 the source package needs to generate a binary development package
5966 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5967 or if you prefer only to support one development version at a
5968 time, <package><var>libraryname</var>-dev</package>. Installing
5969 the development package must result in installation of all the
5970 development files necessary for compiling programs against that
5971 shared library.<footnote>
5972 This wording allows the development files to be split into
5973 several packages, such as a separate architecture-independent
5974 <package><var>libraryname</var>-headers</package>, provided that
5975 the development package depends on all the required additional
5976 packages.
5977 </footnote>
5978 </p>
5981 In case several development versions of a library exist, you may
5982 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5983 <ref id="conflicts">) to ensure that the user only installs one
5984 development version at a time (as different development versions are
5985 likely to have the same header files in them, which would cause a
5986 filename clash if both were unpacked).
5987 </p>
5990 The development package should contain a symlink for the associated
5991 shared library without a version number. For example, the
5992 <package>libgdbm-dev</package> package should include a symlink
5993 from <file>/usr/lib/libgdbm.so</file> to
5994 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5995 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5996 <file>libgdbm.so</file> when compiling dynamically.
5997 </p>
6000 If the package provides Ada Library Information
6001 (<file>*.ali</file>) files for use with GNAT, these files must be
6002 installed read-only (mode 0444) so that GNAT will not attempt to
6003 recompile them. This overrides the normal file mode requirements
6004 given in <ref id="permissions-owners">.
6005 </p>
6006 </sect>
6008 <sect id="sharedlibs-intradeps">
6009 <heading>Dependencies between the packages of the same library</heading>
6012 Typically the development version should have an exact
6013 version dependency on the runtime library, to make sure that
6014 compilation and linking happens correctly. The
6015 <tt>${binary:Version}</tt> substitution variable can be
6016 useful for this purpose.
6017 <footnote>
6018 Previously, <tt>${Source-Version}</tt> was used, but its name
6019 was confusing and it has been deprecated since dpkg 1.13.19.
6020 </footnote>
6021 </p>
6022 </sect>
6024 <sect id="sharedlibs-depends">
6025 <heading>Dependencies between the library and other
6026 packages</heading>
6029 If a package contains a binary or library which links to a
6030 shared library, we must ensure that, when the package is
6031 installed on the system, all of the libraries needed are also
6032 installed. These dependencies must be added to the binary
6033 package when it is built, since they may change based on which
6034 version of a shared library the binary or library was linked
6035 with even if there are no changes to the source of the binary
6036 (for example, symbol versions change, macros become functions or
6037 vice versa, or the binary package may determine at compile-time
6038 whether new library interfaces are available and can be called).
6039 To allow these dependencies to be constructed, shared libraries
6040 must provide either a <file>symbols</file> file or
6041 a <file>shlibs</file> file. These provide information on the
6042 package dependencies required to ensure the presence of
6043 interfaces provided by this library. Any package with binaries
6044 or libraries linking to a shared library must use these files to
6045 determine the required dependencies when it is built. Other
6046 packages which use a shared library (for example using
6047 <tt>dlopen()</tt>) should compute appropriate dependencies
6048 using these files at build time as well.
6049 </p>
6052 The two mechanisms differ in the degree of detail that they
6053 provide. A <file>symbols</file> file documents, for each symbol
6054 exported by a library, the minimal version of the package any
6055 binary using this symbol will need. This is typically the
6056 version of the package in which the symbol was introduced. This
6057 information permits detailed analysis of the symbols used by a
6058 particular package and construction of an accurate dependency,
6059 but it requires the package maintainer to track more information
6060 about the shared library.
6061 </p>
6064 A <file>shlibs</file> file, in contrast, only documents the last
6065 time the library ABI changed in any way. It only provides
6066 information about the library as a whole, not individual
6067 symbols. When a package is built using a shared library with
6068 only a <file>shlibs</file> file, the generated dependency will
6069 require a version of the shared library equal to or newer than
6070 the version of the last ABI change. This generates
6071 unnecessarily restrictive dependencies compared
6072 to <file>symbols</file> files if none of the symbols used by the
6073 package have changed. This, in turn, may make upgrades
6074 needlessly complex and unnecessarily restrict use of the package
6075 on systems with older versions of the shared libraries.
6076 </p>
6079 <file>shlibs</file> files also only support a limited range of
6080 library SONAMEs, making it difficult to use <file>shlibs</file>
6081 files in some unusual corner cases.<footnote>
6082 A <file>shlibs</file> file represents an SONAME as a library
6083 name and version number, such as <tt>libfoo VERSION</tt>,
6084 instead of recording the actual SONAME. If the SONAME doesn't
6085 match one of the two expected formats
6086 (<tt>libfoo-VERSION.so</tt> or <tt>libfoo.so.VERSION</tt>), it
6087 cannot be represented.
6088 </footnote>
6089 </p>
6092 <file>symbols</file> files are therefore recommended for most
6093 shared library packages since they provide more accurate
6094 dependencies. For most C libraries, the additional detail
6095 required by <file>symbols</file> files is not too difficult to
6096 maintain. However, maintaining exhaustive symbols information
6097 for a C++ library can be quite onerous, so <file>shlibs</file>
6098 files may be more appropriate for most C++ libraries. Libraries
6099 with a corresponding udeb must also provide
6100 a <file>shlibs</file> file, since the udeb infrastructure does
6101 not use <file>symbols</file> files.
6102 </p>
6104 <sect1 id="dpkg-shlibdeps">
6105 <heading>Generating dependencies on shared libraries</heading>
6108 When a package that contains any shared libraries or compiled
6109 binaries is built, it must run <prgn>dpkg-shlibdeps</prgn> on
6110 each shared library and compiled binary to determine the
6111 libraries used and hence the dependencies needed by the
6112 package.<footnote>
6113 <prgn>dpkg-shlibdeps</prgn> will use a program
6114 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
6115 the libraries and the symbols in those libraries directly
6116 needed by the binaries or shared libraries in the package.
6117 </footnote>
6118 To do this, put a call to <prgn>dpkg-shlibdeps</prgn> into
6119 your <file>debian/rules</file> file in the source package.
6120 List all of the compiled binaries, libraries, or loadable
6121 modules in your package.<footnote>
6122 The easiest way to call <prgn>dpkg-shlibdeps</prgn>
6123 correctly is to use a package helper framework such
6124 as <package>debhelper</package>. If you are
6125 using <package>debhelper</package>,
6126 the <prgn>dh_shlibdeps</prgn> program will do this work for
6127 you. It will also correctly handle multi-binary packages.
6128 </footnote>
6129 <prgn>dpkg-shlibdeps</prgn> will use the <file>symbols</file>
6130 or <file>shlibs</file> files installed by the shared libraries
6131 to generate dependency information. The package must then
6132 provide a substitution variable into which the discovered
6133 dependency information can be placed.
6134 </p>
6137 If you are creating a udeb for use in the Debian Installer,
6138 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
6139 should use the dependency line of type <tt>udeb</tt> by adding
6140 the <tt>-tudeb</tt> option<footnote>
6141 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
6142 will automatically add this option if it knows it is
6143 processing a udeb.
6144 </footnote>. If there is no dependency line of
6145 type <tt>udeb</tt> in the <file>shlibs</file>
6146 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the
6147 regular dependency line.
6148 </p>
6151 <prgn>dpkg-shlibdeps</prgn> puts the dependency information
6152 into the <file>debian/substvars</file> file by default, which
6153 is then used by <prgn>dpkg-gencontrol</prgn>. You will need
6154 to place a <tt>${shlibs:Depends}</tt> variable in
6155 the <tt>Depends</tt> field in the control file of every binary
6156 package built by this source package that contains compiled
6157 binaries, libraries, or loadable modules. If you have
6158 multiple binary packages, you will need to
6159 call <prgn>dpkg-shlibdeps</prgn> on each one which contains
6160 compiled libraries or binaries. For example, you could use
6161 the <tt>-T</tt> option to the <tt>dpkg</tt> utilities to
6162 specify a different <file>substvars</file> file for each
6163 binary package.<footnote>
6164 Again, <prgn>dh_shlibdeps</prgn>
6165 and <prgn>dh_gencontrol</prgn> will handle everything except
6166 the addition of the variable to the control file for you if
6167 you're using <package>debhelper</package>, including
6168 generating separate <file>substvars</file> files for each
6169 binary package and calling <prgn>dpkg-gencontrol</prgn> with
6170 the appropriate flags.
6171 </footnote>
6172 </p>
6175 For more details on <prgn>dpkg-shlibdeps</prgn>,
6176 see <manref name="dpkg-shlibdeps" section="1">.
6177 </p>
6180 We say that a binary <tt>foo</tt> <em>directly</em> uses a
6181 library <tt>libbar</tt> if it is explicitly linked with that
6182 library (that is, the library is listed in the
6183 ELF <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
6184 to the link line when the binary is created). Other libraries
6185 that are needed by <tt>libbar</tt> are
6186 linked <em>indirectly</em> to <tt>foo</tt>, and the dynamic
6187 linker will load them automatically when it
6188 loads <tt>libbar</tt>. A package should depend on the
6189 libraries it directly uses, but not the libraries it only uses
6190 indirectly. The dependencies for the libraries used
6191 directly will automatically pull in the indirectly-used
6192 libraries. <prgn>dpkg-shlibdeps</prgn> will handle this logic
6193 automatically, but package maintainers need to be aware of
6194 this distinction between directly and indirectly using a
6195 library if they have to override its results for some reason.
6196 <footnote>
6197 A good example of where this helps is the following. We
6198 could update <tt>libimlib</tt> with a new version that
6199 supports a new revision of a graphics format called dgf (but
6200 retaining the same major version number) and depends on a
6201 new library package <package>libdgf4</package> instead of
6202 the older <package>libdgf3</package>. If we
6203 used <prgn>ldd</prgn> to add dependencies for every library
6204 directly or indirectly linked with a binary, every package
6205 that uses <tt>libimlib</tt> would need to be recompiled so
6206 it would also depend on <package>libdgf4</package> in order
6207 to retire the older <package>libdgf3</package> package.
6208 Since dependencies are only added based on
6209 ELF <tt>NEEDED</tt> attribute, packages
6210 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
6211 having the dependency on an appropriate version
6212 of <tt>libdgf</tt> and do not need rebuilding.
6213 </footnote>
6214 </p>
6215 </sect1>
6217 <sect1 id="sharedlibs-updates">
6218 <heading>Shared library ABI changes</heading>
6221 Maintaining a shared library package using
6222 either <file>symbols</file> or <file>shlibs</file> files
6223 requires being aware of the exposed ABI of the shared library
6224 and any changes to it. Both <file>symbols</file>
6225 and <file>shlibs</file> files record every change to the ABI
6226 of the shared library; <file>symbols</file> files do so per
6227 public symbol, whereas <file>shlibs</file> files record only
6228 the last change for the entire library.
6229 </p>
6232 There are two types of ABI changes: ones that are
6233 backward-compatible and ones that are not. An ABI change is
6234 backward-compatible if any reasonable program or library that
6235 was linked with the previous version of the shared library
6236 will still work correctly with the new version of the shared
6237 library.<footnote>
6238 An example of an "unreasonable" program is one that uses
6239 library interfaces that are documented as internal and
6240 unsupported. If the only programs or libraries affected by
6241 a change are "unreasonable" ones, other techniques, such as
6242 declaring <tt>Breaks</tt> relationships with affected
6243 packages or treating their usage of the library as bugs in
6244 those packages, may be appropriate instead of changing the
6245 SONAME. However, the default approach is to change the
6246 SONAME for any change to the ABI that could break a program.
6247 </footnote>
6248 Adding new symbols to the shared library is a
6249 backward-compatible change. Removing symbols from the shared
6250 library is not. Changing the behavior of a symbol may or may
6251 not be backward-compatible depending on the change; for
6252 example, changing a function to accept a new enum constant not
6253 previously used by the library is generally
6254 backward-compatible, but changing the members of a struct that
6255 is passed into library functions is generally not unless the
6256 library takes special precautions to accept old versions of
6257 the data structure.
6258 </p>
6261 ABI changes that are not backward-compatible normally require
6262 changing the <tt>SONAME</tt> of the library and therefore the
6263 shared library package name, which forces rebuilding all
6264 packages using that shared library to update their
6265 dependencies and allow them to use the new version of the
6266 shared library. For more information,
6267 see <ref id="sharedlibs-runtime">. The remainder of this
6268 section will deal with backward-compatible changes.
6269 </p>
6272 Backward-compatible changes require either updating or
6273 recording the <var>minimal-version</var> for that symbol
6274 in <file>symbols</file> files or updating the version in
6275 the <var>dependencies</var> in <file>shlibs</file> files. For
6276 more information on how to do this in the two formats, see
6277 <ref id="symbols"> and <ref id="shlibs">. Below are general
6278 rules that apply to both files.
6279 </p>
6282 The easy case is when a public symbol is added. Simply add
6283 the version at which the symbol was introduced
6284 (for <file>symbols</file> files) or update the dependency
6285 version (for <file>shlibs</file>) files. But special care
6286 should be taken to update dependency versions when the
6287 behavior of a public symbol changes. This is easy to neglect,
6288 since there is no automated method of determining such
6289 changes, but failing to update versions in this case may
6290 result in binary packages with too-weak dependencies that will
6291 fail at runtime, possibly in ways that can cause security
6292 vulnerabilities. If the package maintainer believes that a
6293 symbol behavior change may have occurred but isn't sure, it's
6294 safer to update the version rather than leave it unmodified.
6295 This may result in unnecessarily strict dependencies, but it
6296 ensures that packages whose dependencies are satisfied will
6297 work properly.
6298 </p>
6301 A common example of when a change to the dependency version
6302 is required is a function that takes an enum or struct
6303 argument that controls what the function does. For example:
6304 <example>
6305 enum library_op { OP_FOO, OP_BAR };
6306 int library_do_operation(enum library_op);
6307 </example>
6308 If a new operation, <tt>OP_BAZ</tt>, is added,
6309 the <var>minimal-version</var>
6310 of <tt>library_do_operation</tt> (for <file>symbols</file>
6311 files) or the version in the dependency for the shared library
6312 (for <file>shlibs</file> files) must be increased to the
6313 version at which <tt>OP_BAZ</tt> was introduced. Otherwise, a
6314 binary built against the new version of the library (having
6315 detected at compile-time that the library
6316 supports <tt>OP_BAZ</tt>) may be installed with a shared
6317 library that doesn't support <tt>OP_BAZ</tt> and will fail at
6318 runtime when it tries to pass <tt>OP_BAZ</tt> into this
6319 function.
6320 </p>
6323 Dependency versions in either <file>symbols</file>
6324 or <file>shlibs</file> files normally should not contain the
6325 Debian revision of the package, since the library behavior is
6326 normally fixed for a particular upstream version and any
6327 Debian packaging of that upstream version will have the same
6328 behavior. In the rare case that the library behavior was
6329 changed in a particular Debian revision, appending <tt>~</tt>
6330 to the end of the version that includes the Debian revision is
6331 recommended, since this allows backports of the shared library
6332 package using the normal backport versioning convention to
6333 satisfy the dependency.
6334 </p>
6335 </sect1>
6337 <sect1 id="sharedlibs-symbols">
6338 <heading>The <tt>symbols</tt> system</heading>
6341 In the following sections, we will first describe where the
6342 various <file>symbols</file> files are to be found, then
6343 the <file>symbols</file> file format, and finally how to
6344 create <file>symbols</file> files if your package contains a
6345 shared library.
6346 </p>
6348 <sect2 id="symbols-paths">
6349 <heading>The <file>symbols</file> files present on the
6350 system</heading>
6353 <file>symbols</file> files for a shared library are normally
6354 provided by the shared library package as a control file,
6355 but there are several override paths that are checked first
6356 in case that information is wrong or missing. The following
6357 list gives them in the order in which they are read
6358 by <prgn>dpkg-shlibdeps</prgn> The first one that contains
6359 the required information is used.
6360 <list>
6361 <item>
6362 <p><file>debian/*/DEBIAN/symbols</file></p>
6365 During the package build, if the package itself
6366 contains shared libraries with <file>symbols</file>
6367 files, they will be generated in these staging
6368 directories by <prgn>dpkg-gensymbols</prgn>
6369 (see <ref id="providing-symbols">). <file>symbols</file>
6370 files found in the build tree take precedence
6371 over <file>symbols</file> files from other binary
6372 packages.
6373 </p>
6376 These files must exist
6377 before <prgn>dpkg-shlibdeps</prgn> is run or the
6378 dependencies of binaries and libraries from a source
6379 package on other libraries from that same source
6380 package will not be correct. In practice, this means
6381 that <prgn>dpkg-gensymbols</prgn> must be run
6382 before <prgn>dpkg-shlibdeps</prgn> during the package
6383 build.<footnote>
6384 An example may clarify. Suppose the source
6385 package <tt>foo</tt> generates two binary
6386 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
6387 When building the binary packages, the contents of
6388 the packages are staged in the
6389 directories <file>debian/libfoo2</file>
6390 and <file>debian/foo-runtime</file> respectively.
6391 (<file>debian/tmp</file> could be used instead of
6392 one of these.) Since <tt>libfoo2</tt> provides
6393 the <tt>libfoo</tt> shared library, it will contain
6394 a <tt>symbols</tt> file, which will be installed
6395 in <file>debian/libfoo2/DEBIAN/symbols</file>,
6396 eventually to be included as a control file in that
6397 package. When <prgn>dpkg-shlibdeps</prgn> is run on
6399 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
6400 it will examine
6401 the <file>debian/libfoo2/DEBIAN/symbols</file> file
6402 to determine whether <tt>foo-prog</tt>'s library
6403 dependencies are satisfied by any of the libraries
6404 provided by <tt>libfoo2</tt>. Since those binaries
6405 were linked against the just-built shared library as
6406 part of the build process, the <file>symbols</file>
6407 file for the newly-built <tt>libfoo2</tt> must take
6408 precedence over a <file>symbols</file> file for any
6409 other <tt>libfoo2</tt> package already installed on
6410 the system.
6411 </footnote>
6412 </p>
6413 </item>
6415 <item>
6417 <file>/etc/dpkg/symbols/<var>package</var>.symbols.<var>arch</var></file>
6418 and <file>/etc/dpkg/symbols/<var>package</var>.symbols</file>
6419 </p>
6422 Per-system overrides of shared library dependencies.
6423 These files normally do not exist. They are
6424 maintained by the local system administrator and must
6425 not be created by any Debian package.
6426 </p>
6427 </item>
6429 <item>
6430 <p><file>symbols</file> control files for packages
6431 installed on the system</p>
6434 The <file>symbols</file> control files for all the
6435 packages currently installed on the system are
6436 searched last. This will be the most common source of
6437 shared library dependency information. These are
6438 normally found
6439 in <file>/var/lib/dpkg/info/*.symbols</file>, but
6440 packages should not rely on this and instead should
6441 use <tt>dpkg-query --control-path <var>package</var>
6442 symbols</tt> if for some reason these files need to be
6443 examined.
6444 </p>
6445 </item>
6446 </list>
6447 </p>
6450 Be aware that if a <file>debian/shlibs.local</file> exists
6451 in the source package, it will override
6452 any <file>symbols</file> files. This is the only case where
6453 a <file>shlibs</file> is used despite <file>symbols</file>
6454 files being present. See <ref id="shlibs-paths">
6455 and <ref id="sharedlibs-shlibdeps"> for more information.
6456 </p>
6457 </sect2>
6459 <sect2 id="symbols">
6460 <heading>The <file>symbols</file> File Format</heading>
6463 The following documents the format of
6464 the <file>symbols</file> control file as included in binary
6465 packages. These files are built from
6466 template <file>symbols</file> files in the source package
6467 by <prgn>dpkg-gensymbols</prgn>. The template files support
6468 a richer syntax that allows <prgn>dpkg-gensymbols</prgn> to
6469 do some of the tedious work involved in
6470 maintaining <file>symbols</file> files, such as handling C++
6471 symbols or optional symbols that may not exist on particular
6472 architectures. When writing <file>symbols</file> files for
6473 a shared library package, refer
6474 to <manref name="dpkg-gensymbols" section="1"> for the
6475 richer syntax.
6476 </p>
6479 A <file>symbols</file> may contain one or more entries, one
6480 for each shared library contained in the package
6481 corresponding to that <file>symbols</file>. Each entry has
6482 the following format:
6483 </p>
6486 <example>
6487 <var>library-soname</var> <var>main-dependency-template</var>
6488 [| <var>alternative-dependency-template</var>]
6489 [...]
6490 [* <var>field-name</var>: <var>field-value</var>]
6491 [...]
6492 <var>symbol</var> <var>minimal-version</var>[ <var>id-of-dependency-template</var> ]
6493 </example>
6494 </p>
6497 To explain this format, we'll use the the <tt>zlib1g</tt>
6498 package as an example, which (at the time of writing)
6499 installs the shared
6500 library <file>/usr/lib/libz.so.1.2.3.4</file>. Mandatory
6501 lines will be described first, followed by optional lines.
6502 </p>
6505 <var>library-soname</var> must contain exactly the value of
6506 the ELF <tt>SONAME</tt> attribute of the shared library. In
6507 our example, this is <tt>libz.so.1</tt>.<footnote>
6508 This can be determined by using the command
6509 <example compact="compact">
6510 readelf -d /usr/lib/libz.so.1.2.3.4 | grep SONAME
6511 </example>
6512 </footnote>
6513 </p>
6516 <var>main-dependency-template</var> has the same syntax as a
6517 dependency field in a binary package control file, except
6518 that the string <tt>#MINVER#</tt> is replaced by a version
6519 restriction like <tt>(>= <var>version</var>)</tt> or by
6520 nothing if an unversioned dependency is deemed sufficient.
6521 The version restriction will be based on which symbols from
6522 the shared library are referenced and the version at which
6523 they were introduced (see below). In nearly all
6524 cases, <var>main-dependency-template</var> will
6525 be <tt><var>package</var> #MINVER#</tt>,
6526 where <var>package</var> is the name of the binary package
6527 containing the shared library. This adds a simple,
6528 possibly-versioned dependency on the shared library package.
6529 In some rare cases, such as when multiple packages provide
6530 the same shared library ABI, the dependency template may
6531 need to be more complex.
6532 </p>
6535 In our example, the first line of
6536 the <tt>zlib1g</tt> <file>symbols</file> file would be:
6537 <example compact="compact">
6538 libz.so.1 zlib1g #MINVER#
6539 </example>
6540 </p>
6543 Each public symbol exported by the shared library must have
6544 a corresponding symbol line, indented by one
6545 space. <var>symbol</var> is the exported symbol (which, for
6546 C++, means the mangled symbol) followed by <tt>@</tt> and
6547 the symbol version, or the string <tt>Base</tt> if there is
6548 no symbol version. <var>minimal-version</var> is the most
6549 recent version of the shared library that changed the
6550 behavior of that symbol, whether by adding it, changing its
6551 function signature (the parameters, their types, or the
6552 return type), or changing its behavior in a way that is
6553 visible to a caller.
6554 <var>id-of-dependency-template</var> is an optional
6555 field that references
6556 an <var>alternative-dependency-template</var>; see below for
6557 a full description.
6558 </p>
6561 For example, <tt>libz.so.1</tt> contains the
6562 symbols <tt>compress</tt>
6563 and <tt>compressBound</tt>. <tt>compress</tt> has no symbol
6564 version and last changed its behavior in upstream
6565 version <tt>1:1.1.4</tt>. <tt>compressBound</tt> has the
6566 symbol version <tt>ZLIB_1.2.0</tt>, was introduced in
6567 upstream version <tt>1:1.2.0</tt>, and has not changed its
6568 behavior. Its <file>symbols</file> file therefore contains
6569 the lines:
6570 <example compact="compact">
6571 compress@Base 1:1.1.4
6572 compressBound@ZLIB_1.2.0 1:1.2.0
6573 </example>
6574 Packages using only <tt>compress</tt> would then get a
6575 dependency on <tt>zlib1g (>= 1:1.1.4)</tt>, but packages
6576 using <tt>compressBound</tt> would get a dependency
6577 on <tt>zlib1g (>= 1:1.2.0)</tt>.
6578 </p>
6581 One or more <var>alternative-dependency-template</var> lines
6582 may be provided. These are used in cases where some symbols
6583 in the shared library should use one dependency template
6584 while others should use a different template. The
6585 alternative dependency templates are used only if a symbol
6586 line contains the <var>id-of-dependency-template</var>
6587 field. The first alternative dependency template is
6588 numbered 1, the second 2, and so forth.<footnote>
6589 An example of where this may be needed is with a library
6590 that implements the libGL interface. All GL
6591 implementations provide the same set of base interfaces,
6592 and then may provide some additional interfaces only used
6593 by programs that require that specific GL implementation.
6594 So, for example, libgl1-mesa-glx may use the
6595 following <file>symbols</file> file:
6596 <example>
6597 libGL.so.1 libgl1
6598 | libgl1-mesa-glx #MINVER#
6599 publicGlSymbol@Base 6.3-1
6600 [...]
6601 implementationSpecificSymbol@Base 6.5.2-7 1
6602 [...]
6603 </example>
6604 Binaries or shared libraries using
6605 only <tt>publicGlSymbol</tt> would depend only
6606 on <tt>libgl1</tt> (which may be provided by multiple
6607 packages), but ones
6608 using <tt>implementationSpecificSymbol</tt> would get a
6609 dependency on <tt>libgl1-mesa-glx (>= 6.5.2-7)</tt>
6610 </footnote>
6611 </p>
6614 Finally, the entry for the library may contain one or more
6615 metadata fields. Currently, the only
6616 supported <var>field-name</var>
6617 is <tt>Build-Depends-Package</tt>, whose value lists
6618 the <qref id="sharedlibs-dev">library development
6619 package</qref> on which packages using this shared library
6620 declare a build dependency. If this field is
6621 present, <prgn>dpkg-shlibdeps</prgn> uses it to ensure that
6622 the resulting binary package dependency on the shared
6623 library is at least as strict as the source package
6624 dependency on the shared library development
6625 package.<footnote>
6626 This field should normally not be necessary, since if the
6627 behavior of any symbol has changed, the corresponding
6628 symbol <var>minimal-version</var> should have been
6629 increased. But including it makes the <tt>symbols</tt>
6630 system more robust by tightening the dependency in cases
6631 where the package using the shared library specifically
6632 requires at least a particular version of the shared
6633 library development package for some reason.
6634 </footnote>
6635 For our example, the <tt>zlib1g</tt> <file>symbols</file>
6636 file would contain:
6637 <example compact="compact">
6638 * Build-Depends-Package: zlib1g-dev
6639 </example>
6640 </p>
6643 Also see <manref name="deb-symbols" section="5">.
6644 </p>
6645 </sect2>
6647 <sect2 id="providing-symbols">
6648 <heading>Providing a <file>symbols</file> file</heading>
6651 If your package provides a shared library, you should
6652 arrange to include a <file>symbols</file> control file
6653 following the format described above in that package. You
6654 must include either a <file>symbols</file> control file or
6655 a <file>shlibs</file> control file.
6656 </p>
6659 Normally, this is done by creating a <file>symbols</file> in
6660 the source package
6661 named <file>debian/<var>package</var>.symbols</file>
6662 or <file>debian/symbols</file>, possibly
6663 with <file>.<var>arch</var></file> appended if the symbols
6664 information varies by architecture. This file may use the
6665 extended syntax documented in <manref name="dpkg-gensymbols"
6666 section="1">. Then, call <prgn>dpkg-gensymbols</prgn> as
6667 part of the package build process. It will
6668 create <file>symbols</file> files in the package staging
6669 area based on the binaries and libraries in the package
6670 staging area and the <file>symbols</file> files in the
6671 source package.<footnote>
6672 If you are
6673 using <tt>debhelper</tt>, <prgn>dh_makeshlibs</prgn> will
6674 take care of calling either <prgn>dpkg-gensymbols</prgn>
6675 or generating a <file>shlibs</file> file as appropriate.
6676 </footnote>
6677 </p>
6680 Packages that provide <file>symbols</file> files must keep
6681 them up-to-date to ensure correct dependencies in packages
6682 that use the shared libraries. This means updating
6683 the <file>symbols</file> file whenever a new public symbol
6684 is added, changing the <var>minimal-version</var> field
6685 whenever a symbol changes behavior or signature in a
6686 backward-compatible way (see <ref id="sharedlibs-updates">),
6687 and changing the <var>library-soname</var>
6688 and <var>main-dependency-template</var>, and probably all of
6689 the <var>minimal-version</var> fields, when the library
6690 changes <tt>SONAME</tt>. Removing a public symbol from
6691 the <file>symbols</file> file because it's no longer
6692 provided by the library normally requires changing
6693 the <tt>SONAME</tt> of the library.
6694 See <ref id="sharedlibs-runtime"> for more information
6695 on <tt>SONAME</tt>s.
6696 </p>
6697 </sect2>
6698 </sect1>
6700 <sect1 id="sharedlibs-shlibdeps">
6701 <heading>The <tt>shlibs</tt> system</heading>
6704 The <tt>shlibs</tt> system is a simpler alternative to
6705 the <tt>symbols</tt> system for declaring dependencies for
6706 shared libraries. It may be more appropriate for C++
6707 libraries and other cases where tracking individual symbols is
6708 too difficult. It predated the <tt>symbols</tt> system and is
6709 therefore frequently seen in older packages. It is also
6710 required for udebs, which do not support <tt>symbols</tt>.
6711 </p>
6714 In the following sections, we will first describe where the
6715 various <file>shlibs</file> files are to be found, then how to
6716 use <prgn>dpkg-shlibdeps</prgn>, and finally
6717 the <file>shlibs</file> file format and how to create them.
6718 </p>
6720 <sect2 id="shlibs-paths">
6721 <heading>The <file>shlibs</file> files present on the
6722 system</heading>
6725 There are several places where <tt>shlibs</tt> files are
6726 found. The following list gives them in the order in which
6727 they are read by <prgn>dpkg-shlibdeps</prgn>. (The first
6728 one which gives the required information is used.)
6729 <list>
6730 <item>
6731 <p><file>debian/shlibs.local</file></p>
6734 This lists overrides for this package. This file
6735 should normally not be used, but may be needed
6736 temporarily in unusual situations to work around bugs
6737 in other packages, or in unusual cases where the
6738 normally declared dependency information in the
6739 installed <file>shlibs</file> file for a library
6740 cannot be used. This file overrides information
6741 obtained from any other source.
6742 </p>
6743 </item>
6745 <item>
6746 <p><file>/etc/dpkg/shlibs.override</file></p>
6749 This lists global overrides. This list is normally
6750 empty. It is maintained by the local system
6751 administrator.
6752 </p>
6753 </item>
6755 <item>
6756 <p><file>DEBIAN/shlibs</file> files in the "build
6757 directory"</p>
6760 These files are generated as part of the package build
6761 process and staged for inclusion as control files in
6762 the binary packages being built. They provide details
6763 of any shared libraries included in the same package.
6764 </p>
6765 </item>
6767 <item>
6768 <p><file>shlibs</file> control files for packages
6769 installed on the system</p>
6772 The <file>shlibs</file> control files for all the
6773 packages currently installed on the system. These are
6774 normally found
6775 in <file>/var/lib/dpkg/info/*.shlibs</file>, but
6776 packages should not rely on this and instead should
6777 use <tt>dpkg-query --control-path <var>package</var>
6778 shlibs</tt> if for some reason these files need to be
6779 examined.
6780 </p>
6781 </item>
6783 <item>
6784 <p><file>/etc/dpkg/shlibs.default</file></p>
6787 This file lists any shared libraries whose packages
6788 have failed to provide correct <file>shlibs</file>
6789 files. It was used when the <file>shlibs</file> setup
6790 was first introduced, but it is now normally empty.
6791 It is maintained by the <tt>dpkg</tt> maintainer.
6792 </p>
6793 </item>
6794 </list>
6795 </p>
6798 If a <file>symbols</file> file for a shared library package
6799 is available, <prgn>dpkg-shlibdeps</prgn> will always use it
6800 in preference to a <file>shlibs</file>, with the exception
6801 of <file>debian/shlibs.local</file>. The latter overrides
6802 any other <file>shlibs</file> or <file>symbols</file> files.
6803 </p>
6804 </sect2>
6806 <sect2 id="shlibs">
6807 <heading>The <file>shlibs</file> File Format</heading>
6810 Each <file>shlibs</file> file has the same format. Lines
6811 beginning with <tt>#</tt> are considered to be comments and
6812 are ignored. Each line is of the form:
6813 <example compact="compact">
6814 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
6815 </example>
6816 </p>
6819 We will explain this by reference to the example of the
6820 <tt>zlib1g</tt> package, which (at the time of writing)
6821 installs the shared
6822 library <file>/usr/lib/libz.so.1.2.3.4</file>.
6823 </p>
6826 <var>type</var> is an optional element that indicates the
6827 type of package for which the line is valid. The only type
6828 currently in use is <tt>udeb</tt>. The colon and space
6829 after the type are required.
6830 </p>
6833 <var>library-name</var> is the name of the shared library,
6834 in this case <tt>libz</tt>. (This must match the name part
6835 of the soname, see below.)
6836 </p>
6839 <var>soname-version</var> is the version part of the
6840 ELF <tt>SONAME</tt> attribute of the library, determined the
6841 same way that the <var>soversion</var> component of the
6842 recommended shared library package name is determined.
6843 See <ref id="sharedlibs-runtime"> for the details.
6844 </p>
6847 <var>dependencies</var> has the same syntax as a dependency
6848 field in a binary package control file. It should give
6849 details of which packages are required to satisfy a binary
6850 built against the version of the library contained in the
6851 package. See <ref id="depsyntax"> for details on the
6852 syntax, and <ref id="sharedlibs-updates"> for details on how
6853 to maintain the dependency version constraint.
6854 </p>
6857 In our example, if the last change to the <tt>zlib1g</tt>
6858 package that could change behavior for a client of that
6859 library was in version <tt>1:1.2.3.3.dfsg-1</tt>, then
6860 the <tt>shlibs</tt> entry for this library could say:
6861 <example compact="compact">
6862 libz 1 zlib1g (>= 1:1.2.3.3.dfsg)
6863 </example>
6864 This version restriction must be new enough that any binary
6865 built against the current version of the library will work
6866 with any version of the shared library that satisfies that
6867 dependency.
6868 </p>
6871 As zlib1g also provides a udeb containing the shared
6872 library, there would also be a second line:
6873 <example compact="compact">
6874 udeb: libz 1 zlib1g-udeb (>= 1:1.2.3.3.dfsg)
6875 </example>
6876 </p>
6877 </sect2>
6879 <sect2>
6880 <heading>Providing a <file>shlibs</file> file</heading>
6883 To provide a <file>shlibs</file> file for a shared library
6884 binary package, create a <file>shlibs</file> file following
6885 the format described above and place it in
6886 the <file>DEBIAN</file> directory for that package during
6887 the build. It will then be included as a control file for
6888 that package<footnote>
6889 This is what <prgn>dh_makeshlibs</prgn> in
6890 the <package>debhelper</package> suite does. If your
6891 package also has a udeb that provides a shared
6892 library, <prgn>dh_makeshlibs</prgn> can automatically
6893 generate the <tt>udeb:</tt> lines if you specify the name
6894 of the udeb with the <tt>--add-udeb</tt> option.
6895 </footnote>.
6896 </p>
6899 Since <prgn>dpkg-shlibdeps</prgn> reads
6900 the <file>DEBIAN/shlibs</file> files in all of the binary
6901 packages being built from this source package, all of
6902 the <file>DEBIAN/shlibs</file> files should be installed
6903 before <prgn>dpkg-shlibdeps</prgn> is called on any of the
6904 binary packages.
6905 </p>
6906 </sect2>
6907 </sect1>
6908 </sect>
6909 </chapt>
6912 <chapt id="opersys"><heading>The Operating System</heading>
6914 <sect>
6915 <heading>File system hierarchy</heading>
6918 <sect1 id="fhs">
6919 <heading>File System Structure</heading>
6922 The location of all files and directories must comply with the
6923 Filesystem Hierarchy Standard (FHS), version 2.3, with the
6924 exceptions noted below, and except where doing so would
6925 violate other terms of Debian Policy. The following
6926 exceptions to the FHS apply:
6928 <enumlist>
6929 <item>
6931 The FHS requirement that architecture-independent
6932 application-specific static files be located in
6933 <file>/usr/share</file> is relaxed to a suggestion.
6935 In particular, a subdirectory of <file>/usr/lib</file> may
6936 be used by a package (or a collection of packages) to hold a
6937 mixture of architecture-independent and
6938 architecture-dependent files. However, when a directory is
6939 entirely composed of architecture-independent files, it
6940 should be located in <file>/usr/share</file>.
6941 </p>
6942 </item>
6943 <item>
6945 The optional rules related to user specific
6946 configuration files for applications are stored in
6947 the user's home directory are relaxed. It is
6948 recommended that such files start with the
6949 '<tt>.</tt>' character (a "dot file"), and if an
6950 application needs to create more than one dot file
6951 then the preferred placement is in a subdirectory
6952 with a name starting with a '.' character, (a "dot
6953 directory"). In this case it is recommended the
6954 configuration files not start with the '.'
6955 character.
6956 </p>
6957 </item>
6958 <item>
6960 The requirement for amd64 to use <file>/lib64</file>
6961 for 64 bit binaries is removed.
6962 </p>
6963 </item>
6964 <item>
6966 The requirement for object files, internal binaries, and
6967 libraries, including <file>libc.so.*</file>, to be located
6968 directly under <file>/lib{,32}</file> and
6969 <file>/usr/lib{,32}</file> is amended, permitting files
6970 to instead be installed to
6971 <file>/lib/<var>triplet</var></file> and
6972 <file>/usr/lib/<var>triplet</var></file>, where
6973 <tt><var>triplet</var></tt> is the value returned by
6974 <tt>dpkg-architecture -qDEB_HOST_MULTIARCH</tt> for the
6975 architecture of the package. Packages may <em>not</em>
6976 install files to any <var>triplet</var> path other
6977 than the one matching the architecture of that package;
6978 for instance, an <tt>Architecture: amd64</tt> package
6979 containing 32-bit x86 libraries may not install these
6980 libraries to <file>/usr/lib/i386-linux-gnu</file>.
6981 <footnote>
6982 This is necessary in order to reserve the directories for
6983 use in cross-installation of library packages from other
6984 architectures, as part of <tt>multiarch</tt>.
6985 </footnote>
6986 </p>
6988 The requirement for C and C++ headers files to be
6989 accessible through the search path
6990 <file>/usr/include/</file> is amended, permitting files to
6991 be accessible through the search path
6992 <file>/usr/include/<var>triplet</var></file> where
6993 <tt><var>triplet</var></tt> is as above. <footnote>
6994 This is necessary for architecture-dependant headers
6995 file to coexist in a <tt>multiarch</tt> setup.
6996 </footnote>
6997 </p>
6999 Applications may also use a single subdirectory under
7000 <file>/usr/lib/<var>triplet</var></file>.
7001 </p>
7003 The execution time linker/loader, ld*, must still be made
7004 available in the existing location under /lib or /lib64
7005 since this is part of the ELF ABI for the architecture.
7006 </p>
7007 </item>
7008 <item>
7010 The requirement that
7011 <file>/usr/local/share/man</file> be "synonymous"
7012 with <file>/usr/local/man</file> is relaxed to a
7013 recommendation</p>
7014 </item>
7015 <item>
7017 The requirement that windowmanagers with a single
7018 configuration file call it <file>system.*wmrc</file>
7019 is removed, as is the restriction that the window
7020 manager subdirectory be named identically to the
7021 window manager name itself.
7022 </p>
7023 </item>
7024 <item>
7026 The requirement that boot manager configuration
7027 files live in <file>/etc</file>, or at least are
7028 symlinked there, is relaxed to a recommendation.
7029 </p>
7030 </item>
7031 <item>
7033 The additional directory <file>/run</file> in the root
7034 file system is allowed. <file>/run</file>
7035 replaces <file>/var/run</file>, and the
7036 subdirectory <file>/run/lock</file>
7037 replaces <file>/var/lock</file>, with
7038 the <file>/var</file> directories replaced by symlinks
7039 for backwards compatibility. <file>/run</file>
7040 and <file>/run/lock</file> must follow all of the
7041 requirements in the FHS for <file>/var/run</file>
7042 and <file>/var/lock</file>, respectively, such as file
7043 naming conventions, file format requirements, or the
7044 requirement that files be cleared during the boot
7045 process. Files and directories residing
7046 in <file>/run</file> should be stored on a temporary
7047 file system.
7048 </p>
7050 Packages must not assume the <file>/run</file>
7051 directory exists or is usable without a dependency
7052 on <tt>initscripts (>= 2.88dsf-13.3)</tt> until the
7053 stable release of Debian supports <file>/run</file>.
7054 </p>
7055 </item>
7056 <item>
7058 The <file>/sys</file> directory in the root filesystem is
7059 additionally allowed. <footnote>This directory is used as
7060 mount point to mount virtual filesystems to get access to
7061 kernel information.</footnote>
7062 </p>
7063 </item>
7064 <item>
7066 The <file>/var/www</file> directory is additionally allowed.
7067 </p>
7068 </item>
7069 <item>
7071 The requirement for <file>/usr/local/lib&lt;qual&gt;</file>
7072 to exist if <file>/lib&lt;qual&gt;</file> or
7073 <file>/usr/lib&lt;qual&gt;</file> exists (where
7074 <file>lib&lt;qual&gt;</file> is a variant of
7075 <file>lib</file> such as <file>lib32</file> or
7076 <file>lib64</file>) is removed.
7077 </p>
7078 </item>
7079 <item>
7081 On GNU/Hurd systems, the following additional
7082 directories are allowed in the root
7083 filesystem: <file>/hurd</file>
7084 and <file>/servers</file>.<footnote>
7085 These directories are used to store translators and as
7086 a set of standard names for mount points,
7087 respectively.
7088 </footnote>
7089 </p>
7090 </item>
7091 </enumlist>
7092 </p>
7095 The version of this document referred here can be
7096 found in the <tt>debian-policy</tt> package or on <url
7097 id="http://www.debian.org/doc/packaging-manuals/fhs/"
7098 name="FHS (Debian copy)"> alongside this manual (or, if
7099 you have the <package>debian-policy</package> installed,
7100 you can try <url
7101 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
7102 (local copy)">). The
7103 latest version, which may be a more recent version, may
7104 be found on
7105 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
7106 Specific questions about following the standard may be
7107 asked on the <tt>debian-devel</tt> mailing list, or
7108 referred to the FHS mailing list (see the
7109 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
7110 more information).
7111 </p>
7112 </sect1>
7114 <sect1>
7115 <heading>Site-specific programs</heading>
7118 As mandated by the FHS, packages must not place any
7119 files in <file>/usr/local</file>, either by putting them in
7120 the file system archive to be unpacked by <prgn>dpkg</prgn>
7121 or by manipulating them in their maintainer scripts.
7122 </p>
7125 However, the package may create empty directories below
7126 <file>/usr/local</file> so that the system administrator knows
7127 where to place site-specific files. These are not
7128 directories <em>in</em> <file>/usr/local</file>, but are
7129 children of directories in <file>/usr/local</file>. These
7130 directories (<file>/usr/local/*/dir/</file>)
7131 should be removed on package removal if they are
7132 empty.
7133 </p>
7136 Note that this applies only to
7137 directories <em>below</em> <file>/usr/local</file>,
7138 not <em>in</em> <file>/usr/local</file>. Packages must
7139 not create sub-directories in the
7140 directory <file>/usr/local</file> itself, except those
7141 listed in FHS, section 4.5. However, you may create
7142 directories below them as you wish. You must not remove
7143 any of the directories listed in 4.5, even if you created
7144 them.
7145 </p>
7148 Since <file>/usr/local</file> can be mounted read-only from a
7149 remote server, these directories must be created and
7150 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
7151 maintainer scripts and not be included in the
7152 <file>.deb</file> archive. These scripts must not fail if
7153 either of these operations fail.
7154 </p>
7157 For example, the <tt>emacsen-common</tt> package could
7158 contain something like
7159 <example compact="compact">
7160 if [ ! -e /usr/local/share/emacs ]; then
7161 if mkdir /usr/local/share/emacs 2>/dev/null; then
7162 if chown root:staff /usr/local/share/emacs; then
7163 chmod 2775 /usr/local/share/emacs || true
7167 </example>
7168 in its <prgn>postinst</prgn> script, and
7169 <example compact="compact">
7170 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
7171 rmdir /usr/local/share/emacs 2>/dev/null || true
7172 </example>
7173 in the <prgn>prerm</prgn> script. (Note that this form is
7174 used to ensure that if the script is interrupted, the
7175 directory <file>/usr/local/share/emacs</file> will still be
7176 removed.)
7177 </p>
7180 If you do create a directory in <file>/usr/local</file> for
7181 local additions to a package, you should ensure that
7182 settings in <file>/usr/local</file> take precedence over the
7183 equivalents in <file>/usr</file>.
7184 </p>
7187 However, because <file>/usr/local</file> and its contents are
7188 for exclusive use of the local administrator, a package
7189 must not rely on the presence or absence of files or
7190 directories in <file>/usr/local</file> for normal operation.
7191 </p>
7194 The <file>/usr/local</file> directory itself and all the
7195 subdirectories created by the package should (by default) have
7196 permissions 2775 (group-writable and set-group-id) and be
7197 owned by <tt>root:staff</tt>.
7198 </p>
7199 </sect1>
7201 <sect1>
7202 <heading>The system-wide mail directory</heading>
7204 The system-wide mail directory
7205 is <file>/var/mail</file>. This directory is part of the
7206 base system and should not be owned by any particular mail
7207 agents. The use of the old
7208 location <file>/var/spool/mail</file> is deprecated, even
7209 though the spool may still be physically located there.
7210 </p>
7211 </sect1>
7213 <sect1 id="fhs-run">
7214 <heading><file>/run</file> and <file>/run/lock</file></heading>
7217 The directory <file>/run</file> is cleared at boot, normally
7218 by being a mount point for a temporary file system. Packages
7219 therefore must not assume that any files or directories
7220 under <file>/run</file> other than <file>/run/lock</file>
7221 exist unless the package has arranged to create those files or
7222 directories since the last reboot. Normally, this is done by
7223 the package via an init script. See <ref id="writing-init">
7224 for more information.
7225 </p>
7228 Packages must not include files or directories
7229 under <file>/run</file>, or under the
7230 older <file>/var/run</file> and <file>/var/lock</file> paths.
7231 The latter paths will normally be symlinks or other
7232 redirections to <file>/run</file> for backwards compatibility.
7233 </p>
7234 </sect1>
7235 </sect>
7237 <sect>
7238 <heading>Users and groups</heading>
7240 <sect1>
7241 <heading>Introduction</heading>
7243 The Debian system can be configured to use either plain or
7244 shadow passwords.
7245 </p>
7248 Some user ids (UIDs) and group ids (GIDs) are reserved
7249 globally for use by certain packages. Because some
7250 packages need to include files which are owned by these
7251 users or groups, or need the ids compiled into binaries,
7252 these ids must be used on any Debian system only for the
7253 purpose for which they are allocated. This is a serious
7254 restriction, and we should avoid getting in the way of
7255 local administration policies. In particular, many sites
7256 allocate users and/or local system groups starting at 100.
7257 </p>
7260 Apart from this we should have dynamically allocated ids,
7261 which should by default be arranged in some sensible
7262 order, but the behavior should be configurable.
7263 </p>
7266 Packages other than <tt>base-passwd</tt> must not modify
7267 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
7268 <file>/etc/group</file> or <file>/etc/gshadow</file>.
7269 </p>
7270 </sect1>
7272 <sect1>
7273 <heading>UID and GID classes</heading>
7275 The UID and GID numbers are divided into classes as
7276 follows:
7277 <taglist>
7278 <tag>0-99:</tag>
7279 <item>
7281 Globally allocated by the Debian project, the same
7282 on every Debian system. These ids will appear in
7283 the <file>passwd</file> and <file>group</file> files of all
7284 Debian systems, new ids in this range being added
7285 automatically as the <tt>base-passwd</tt> package is
7286 updated.
7287 </p>
7290 Packages which need a single statically allocated
7291 uid or gid should use one of these; their
7292 maintainers should ask the <tt>base-passwd</tt>
7293 maintainer for ids.
7294 </p>
7295 </item>
7297 <tag>100-999:</tag>
7298 <item>
7300 Dynamically allocated system users and groups.
7301 Packages which need a user or group, but can have
7302 this user or group allocated dynamically and
7303 differently on each system, should use <tt>adduser
7304 --system</tt> to create the group and/or user.
7305 <prgn>adduser</prgn> will check for the existence of
7306 the user or group, and if necessary choose an unused
7307 id based on the ranges specified in
7308 <file>adduser.conf</file>.
7309 </p>
7310 </item>
7312 <tag>1000-59999:</tag>
7313 <item>
7315 Dynamically allocated user accounts. By default
7316 <prgn>adduser</prgn> will choose UIDs and GIDs for
7317 user accounts in this range, though
7318 <file>adduser.conf</file> may be used to modify this
7319 behavior.
7320 </p>
7321 </item>
7323 <tag>60000-64999:</tag>
7324 <item>
7326 Globally allocated by the Debian project, but only
7327 created on demand. The ids are allocated centrally
7328 and statically, but the actual accounts are only
7329 created on users' systems on demand.
7330 </p>
7333 These ids are for packages which are obscure or
7334 which require many statically-allocated ids. These
7335 packages should check for and create the accounts in
7336 <file>/etc/passwd</file> or <file>/etc/group</file> (using
7337 <prgn>adduser</prgn> if it has this facility) if
7338 necessary. Packages which are likely to require
7339 further allocations should have a "hole" left after
7340 them in the allocation, to give them room to
7341 grow.
7342 </p>
7343 </item>
7345 <tag>65000-65533:</tag>
7346 <item>
7347 <p>Reserved.</p>
7348 </item>
7350 <tag>65534:</tag>
7351 <item>
7353 User <tt>nobody</tt>. The corresponding gid refers
7354 to the group <tt>nogroup</tt>.
7355 </p>
7356 </item>
7358 <tag>65535:</tag>
7359 <item>
7361 This value <em>must not</em> be used, because it was
7362 the error return sentinel value when <tt>uid_t</tt>
7363 was 16 bits.
7364 </p>
7365 </item>
7367 <tag>65536-4294967293:</tag>
7368 <item>
7370 Dynamically allocated user accounts. By
7371 default <prgn>adduser</prgn> will not allocate UIDs
7372 and GIDs in this range, to ease compatibility with
7373 legacy systems where <tt>uid_t</tt> is still 16
7374 bits.
7375 </p>
7376 </item>
7378 <tag>4294967294:</tag>
7379 <item>
7381 <tt>(uid_t)(-2) == (gid_t)(-2)</tt> <em>must not</em> be
7382 used, because it is used as the anonymous, unauthenticated
7383 user by some NFS implementations.
7384 </p>
7385 </item>
7387 <tag>4294967295:</tag>
7388 <item>
7390 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
7391 not</em> be used, because it is the error return
7392 sentinel value.
7393 </p>
7394 </item>
7395 </taglist>
7396 </p>
7397 </sect1>
7398 </sect>
7400 <sect id="sysvinit">
7401 <heading>System run levels and <file>init.d</file> scripts</heading>
7403 <sect1 id="/etc/init.d">
7404 <heading>Introduction</heading>
7407 The <file>/etc/init.d</file> directory contains the scripts
7408 executed by <prgn>init</prgn> at boot time and when the
7409 init state (or "runlevel") is changed (see <manref
7410 name="init" section="8">).
7411 </p>
7414 There are at least two different, yet functionally
7415 equivalent, ways of handling these scripts. For the sake
7416 of simplicity, this document describes only the symbolic
7417 link method. However, it must not be assumed by maintainer
7418 scripts that this method is being used, and any automated
7419 manipulation of the various runlevel behaviors by
7420 maintainer scripts must be performed using
7421 <prgn>update-rc.d</prgn> as described below and not by
7422 manually installing or removing symlinks. For information
7423 on the implementation details of the other method,
7424 implemented in the <tt>file-rc</tt> package, please refer
7425 to the documentation of that package.
7426 </p>
7429 These scripts are referenced by symbolic links in the
7430 <file>/etc/rc<var>n</var>.d</file> directories. When changing
7431 runlevels, <prgn>init</prgn> looks in the directory
7432 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
7433 execute, where <tt><var>n</var></tt> is the runlevel that
7434 is being changed to, or <tt>S</tt> for the boot-up
7435 scripts.
7436 </p>
7439 The names of the links all have the form
7440 <file>S<var>mm</var><var>script</var></file> or
7441 <file>K<var>mm</var><var>script</var></file> where
7442 <var>mm</var> is a two-digit number and <var>script</var>
7443 is the name of the script (this should be the same as the
7444 name of the actual script in <file>/etc/init.d</file>).
7445 </p>
7448 When <prgn>init</prgn> changes runlevel first the targets
7449 of the links whose names start with a <tt>K</tt> are
7450 executed, each with the single argument <tt>stop</tt>,
7451 followed by the scripts prefixed with an <tt>S</tt>, each
7452 with the single argument <tt>start</tt>. (The links are
7453 those in the <file>/etc/rc<var>n</var>.d</file> directory
7454 corresponding to the new runlevel.) The <tt>K</tt> links
7455 are responsible for killing services and the <tt>S</tt>
7456 link for starting services upon entering the runlevel.
7457 </p>
7460 For example, if we are changing from runlevel 2 to
7461 runlevel 3, init will first execute all of the <tt>K</tt>
7462 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
7463 all of the <tt>S</tt> prefixed scripts in that directory.
7464 The links starting with <tt>K</tt> will cause the
7465 referred-to file to be executed with an argument of
7466 <tt>stop</tt>, and the <tt>S</tt> links with an argument
7467 of <tt>start</tt>.
7468 </p>
7471 The two-digit number <var>mm</var> is used to determine
7472 the order in which to run the scripts: low-numbered links
7473 have their scripts run first. For example, the
7474 <tt>K20</tt> scripts will be executed before the
7475 <tt>K30</tt> scripts. This is used when a certain service
7476 must be started before another. For example, the name
7477 server <prgn>bind</prgn> might need to be started before
7478 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
7479 can set up its access lists. In this case, the script
7480 that starts <prgn>bind</prgn> would have a lower number
7481 than the script that starts <prgn>inn</prgn> so that it
7482 runs first:
7483 <example compact="compact">
7484 /etc/rc2.d/S17bind
7485 /etc/rc2.d/S70inn
7486 </example>
7487 </p>
7490 The two runlevels 0 (halt) and 6 (reboot) are slightly
7491 different. In these runlevels, the links with an
7492 <tt>S</tt> prefix are still called after those with a
7493 <tt>K</tt> prefix, but they too are called with the single
7494 argument <tt>stop</tt>.
7495 </p>
7496 </sect1>
7498 <sect1 id="writing-init">
7499 <heading>Writing the scripts</heading>
7502 Packages that include daemons for system services should
7503 place scripts in <file>/etc/init.d</file> to start or stop
7504 services at boot time or during a change of runlevel.
7505 These scripts should be named
7506 <file>/etc/init.d/<var>package</var></file>, and they should
7507 accept one argument, saying what to do:
7509 <taglist>
7510 <tag><tt>start</tt></tag>
7511 <item>start the service,</item>
7513 <tag><tt>stop</tt></tag>
7514 <item>stop the service,</item>
7516 <tag><tt>restart</tt></tag>
7517 <item>stop and restart the service if it's already running,
7518 otherwise start the service</item>
7520 <tag><tt>reload</tt></tag>
7521 <item><p>cause the configuration of the service to be
7522 reloaded without actually stopping and restarting
7523 the service,</item>
7525 <tag><tt>force-reload</tt></tag>
7526 <item>cause the configuration to be reloaded if the
7527 service supports this, otherwise restart the
7528 service.</item>
7529 </taglist>
7531 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
7532 <tt>force-reload</tt> options should be supported by all
7533 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
7534 option is optional.
7535 </p>
7538 The <file>init.d</file> scripts must ensure that they will
7539 behave sensibly (i.e., returning success and not starting
7540 multiple copies of a service) if invoked with <tt>start</tt>
7541 when the service is already running, or with <tt>stop</tt>
7542 when it isn't, and that they don't kill unfortunately-named
7543 user processes. The best way to achieve this is usually to
7544 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
7545 option.
7546 </p>
7549 Be careful of using <tt>set -e</tt> in <file>init.d</file>
7550 scripts. Writing correct <file>init.d</file> scripts requires
7551 accepting various error exit statuses when daemons are already
7552 running or already stopped without aborting
7553 the <file>init.d</file> script, and common <file>init.d</file>
7554 function libraries are not safe to call with <tt>set -e</tt>
7555 in effect<footnote>
7556 <tt>/lib/lsb/init-functions</tt>, which assists in writing
7557 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
7558 in effect and echoing status messages to the console fails,
7559 for example.
7560 </footnote>. For <tt>init.d</tt> scripts, it's often easier
7561 to not use <tt>set -e</tt> and instead check the result of
7562 each command separately.
7563 </p>
7566 If a service reloads its configuration automatically (as
7567 in the case of <prgn>cron</prgn>, for example), the
7568 <tt>reload</tt> option of the <file>init.d</file> script
7569 should behave as if the configuration has been reloaded
7570 successfully.
7571 </p>
7574 The <file>/etc/init.d</file> scripts must be treated as
7575 configuration files, either (if they are present in the
7576 package, that is, in the .deb file) by marking them as
7577 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
7578 by managing them correctly in the maintainer scripts (see
7579 <ref id="config-files">). This is important since we want
7580 to give the local system administrator the chance to adapt
7581 the scripts to the local system, e.g., to disable a
7582 service without de-installing the package, or to specify
7583 some special command line options when starting a service,
7584 while making sure their changes aren't lost during the next
7585 package upgrade.
7586 </p>
7589 These scripts should not fail obscurely when the
7590 configuration files remain but the package has been
7591 removed, as configuration files remain on the system after
7592 the package has been removed. Only when <prgn>dpkg</prgn>
7593 is executed with the <tt>--purge</tt> option will
7594 configuration files be removed. In particular, as the
7595 <file>/etc/init.d/<var>package</var></file> script itself is
7596 usually a <tt>conffile</tt>, it will remain on the system
7597 if the package is removed but not purged. Therefore, you
7598 should include a <tt>test</tt> statement at the top of the
7599 script, like this:
7600 <example compact="compact">
7601 test -f <var>program-executed-later-in-script</var> || exit 0
7602 </example>
7603 </p>
7606 Often there are some variables in the <file>init.d</file>
7607 scripts whose values control the behavior of the scripts,
7608 and which a system administrator is likely to want to
7609 change. As the scripts themselves are frequently
7610 <tt>conffile</tt>s, modifying them requires that the
7611 administrator merge in their changes each time the package
7612 is upgraded and the <tt>conffile</tt> changes. To ease
7613 the burden on the system administrator, such configurable
7614 values should not be placed directly in the script.
7615 Instead, they should be placed in a file in
7616 <file>/etc/default</file>, which typically will have the same
7617 base name as the <file>init.d</file> script. This extra file
7618 should be sourced by the script when the script runs. It
7619 must contain only variable settings and comments in SUSv3
7620 <prgn>sh</prgn> format. It may either be a
7621 <tt>conffile</tt> or a configuration file maintained by
7622 the package maintainer scripts. See <ref id="config-files">
7623 for more details.
7624 </p>
7627 To ensure that vital configurable values are always
7628 available, the <file>init.d</file> script should set default
7629 values for each of the shell variables it uses, either
7630 before sourcing the <file>/etc/default/</file> file or
7631 afterwards using something like the <tt>:
7632 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
7633 script must behave sensibly and not fail if the
7634 <file>/etc/default</file> file is deleted.
7635 </p>
7638 Files and directories under <file>/run</file>, including ones
7639 referred to via the compatibility paths <file>/var/run</file>
7640 and <file>/var/lock</file>, are normally stored on a temporary
7641 filesystem and are normally not persistent across a reboot.
7642 The <file>init.d</file> scripts must handle this correctly.
7643 This will typically mean creating any required subdirectories
7644 dynamically when the <file>init.d</file> script is run.
7645 See <ref id="fhs-run"> for more information.
7646 </p>
7647 </sect1>
7649 <sect1>
7650 <heading>Interfacing with the initscript system</heading>
7653 Maintainers should use the abstraction layer provided by
7654 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
7655 programs to deal with initscripts in their packages'
7656 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
7657 and <prgn>postrm</prgn>.
7658 </p>
7661 Directly managing the /etc/rc?.d links and directly
7662 invoking the <file>/etc/init.d/</file> initscripts should
7663 be done only by packages providing the initscript
7664 subsystem (such as <prgn>sysv-rc</prgn> and
7665 <prgn>file-rc</prgn>).
7666 </p>
7668 <sect2>
7669 <heading>Managing the links</heading>
7672 The program <prgn>update-rc.d</prgn> is provided for
7673 package maintainers to arrange for the proper creation and
7674 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
7675 or their functional equivalent if another method is being
7676 used. This may be used by maintainers in their packages'
7677 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
7678 </p>
7681 You must not include any <file>/etc/rc<var>n</var>.d</file>
7682 symbolic links in the actual archive or manually create or
7683 remove the symbolic links in maintainer scripts; you must
7684 use the <prgn>update-rc.d</prgn> program instead. (The
7685 former will fail if an alternative method of maintaining
7686 runlevel information is being used.) You must not include
7687 the <file>/etc/rc<var>n</var>.d</file> directories themselves
7688 in the archive either. (Only the <tt>sysvinit</tt>
7689 package may do so.)
7690 </p>
7693 By default <prgn>update-rc.d</prgn> will start services in
7694 each of the multi-user state runlevels (2, 3, 4, and 5)
7695 and stop them in the halt runlevel (0), the single-user
7696 runlevel (1) and the reboot runlevel (6). The system
7697 administrator will have the opportunity to customize
7698 runlevels by simply adding, moving, or removing the
7699 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
7700 symbolic links are being used, or by modifying
7701 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
7702 is being used.
7703 </p>
7706 To get the default behavior for your package, put in your
7707 <prgn>postinst</prgn> script
7708 <example compact="compact">
7709 update-rc.d <var>package</var> defaults
7710 </example>
7711 and in your <prgn>postrm</prgn>
7712 <example compact="compact">
7713 if [ "$1" = purge ]; then
7714 update-rc.d <var>package</var> remove
7716 </example>. Note that if your package changes runlevels
7717 or priority, you may have to remove and recreate the links,
7718 since otherwise the old links may persist. Refer to the
7719 documentation of <prgn>update-rc.d</prgn>.
7720 </p>
7723 This will use a default sequence number of 20. If it does
7724 not matter when or in which order the <file>init.d</file>
7725 script is run, use this default. If it does, then you
7726 should talk to the maintainer of the <prgn>sysvinit</prgn>
7727 package or post to <tt>debian-devel</tt>, and they will
7728 help you choose a number.
7729 </p>
7732 For more information about using <tt>update-rc.d</tt>,
7733 please consult its man page <manref name="update-rc.d"
7734 section="8">.
7735 </p>
7736 </sect2>
7738 <sect2>
7739 <heading>Running initscripts</heading>
7741 The program <prgn>invoke-rc.d</prgn> is provided to make
7742 it easier for package maintainers to properly invoke an
7743 initscript, obeying runlevel and other locally-defined
7744 constraints that might limit a package's right to start,
7745 stop and otherwise manage services. This program may be
7746 used by maintainers in their packages' scripts.
7747 </p>
7750 The package maintainer scripts must use
7751 <prgn>invoke-rc.d</prgn> to invoke the
7752 <file>/etc/init.d/*</file> initscripts, instead of
7753 calling them directly.
7754 </p>
7757 By default, <prgn>invoke-rc.d</prgn> will pass any
7758 action requests (start, stop, reload, restart...) to the
7759 <file>/etc/init.d</file> script, filtering out requests
7760 to start or restart a service out of its intended
7761 runlevels.
7762 </p>
7765 Most packages will simply need to change:
7766 <example compact="compact">/etc/init.d/&lt;package&gt;
7767 &lt;action&gt;</example> in their <prgn>postinst</prgn>
7768 and <prgn>prerm</prgn> scripts to:
7769 <example compact="compact">
7770 if which invoke-rc.d >/dev/null 2>&1; then
7771 invoke-rc.d <var>package</var> &lt;action&gt;
7772 else
7773 /etc/init.d/<var>package</var> &lt;action&gt;
7775 </example>
7776 </p>
7779 A package should register its initscript services using
7780 <prgn>update-rc.d</prgn> before it tries to invoke them
7781 using <prgn>invoke-rc.d</prgn>. Invocation of
7782 unregistered services may fail.
7783 </p>
7786 For more information about using
7787 <prgn>invoke-rc.d</prgn>, please consult its man page
7788 <manref name="invoke-rc.d" section="8">.
7789 </p>
7790 </sect2>
7791 </sect1>
7793 <sect1>
7794 <heading>Boot-time initialization</heading>
7797 There used to be another directory, <file>/etc/rc.boot</file>,
7798 which contained scripts which were run once per machine
7799 boot. This has been deprecated in favour of links from
7800 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
7801 described in <ref id="/etc/init.d">. Packages must not
7802 place files in <file>/etc/rc.boot</file>.
7803 </p>
7804 </sect1>
7806 <sect1>
7807 <heading>Example</heading>
7810 An example on which you can base your
7811 <file>/etc/init.d</file> scripts is found in
7812 <file>/etc/init.d/skeleton</file>.
7813 </p>
7815 </sect1>
7816 </sect>
7818 <sect>
7819 <heading>Console messages from <file>init.d</file> scripts</heading>
7822 This section describes the formats to be used for messages
7823 written to standard output by the <file>/etc/init.d</file>
7824 scripts. The intent is to improve the consistency of
7825 Debian's startup and shutdown look and feel. For this
7826 reason, please look very carefully at the details. We want
7827 the messages to have the same format in terms of wording,
7828 spaces, punctuation and case of letters.
7829 </p>
7832 Here is a list of overall rules that should be used for
7833 messages generated by <file>/etc/init.d</file> scripts.
7834 </p>
7837 <list>
7838 <item>
7839 The message should fit in one line (fewer than 80
7840 characters), start with a capital letter and end with
7841 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
7842 </item>
7844 <item>
7845 If the script is performing some time consuming task in
7846 the background (not merely starting or stopping a
7847 program, for instance), an ellipsis (three dots:
7848 <tt>...</tt>) should be output to the screen, with no
7849 leading or tailing whitespace or line feeds.
7850 </item>
7852 <item>
7853 The messages should appear as if the computer is telling
7854 the user what it is doing (politely :-), but should not
7855 mention "it" directly. For example, instead of:
7856 <example compact="compact">
7857 I'm starting network daemons: nfsd mountd.
7858 </example>
7859 the message should say
7860 <example compact="compact">
7861 Starting network daemons: nfsd mountd.
7862 </example>
7863 </item>
7864 </list>
7865 </p>
7868 <tt>init.d</tt> script should use the following standard
7869 message formats for the situations enumerated below.
7870 </p>
7873 <list>
7874 <item>
7875 <p>When daemons are started</p>
7878 If the script starts one or more daemons, the output
7879 should look like this (a single line, no leading
7880 spaces):
7881 <example compact="compact">
7882 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
7883 </example>
7884 The <var>description</var> should describe the
7885 subsystem the daemon or set of daemons are part of,
7886 while <var>daemon-1</var> up to <var>daemon-n</var>
7887 denote each daemon's name (typically the file name of
7888 the program).
7889 </p>
7892 For example, the output of <file>/etc/init.d/lpd</file>
7893 would look like:
7894 <example compact="compact">
7895 Starting printer spooler: lpd.
7896 </example>
7897 </p>
7900 This can be achieved by saying
7901 <example compact="compact">
7902 echo -n "Starting printer spooler: lpd"
7903 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
7904 echo "."
7905 </example>
7906 in the script. If there are more than one daemon to
7907 start, the output should look like this:
7908 <example compact="compact">
7909 echo -n "Starting remote file system services:"
7910 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
7911 echo -n " mountd"; start-stop-daemon --start --quiet mountd
7912 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
7913 echo "."
7914 </example>
7915 This makes it possible for the user to see what is
7916 happening and when the final daemon has been started.
7917 Care should be taken in the placement of white spaces:
7918 in the example above the system administrators can
7919 easily comment out a line if they don't want to start
7920 a specific daemon, while the displayed message still
7921 looks good.
7922 </p>
7923 </item>
7925 <item>
7926 <p>When a system parameter is being set</p>
7929 If you have to set up different system parameters
7930 during the system boot, you should use this format:
7931 <example compact="compact">
7932 Setting <var>parameter</var> to "<var>value</var>".
7933 </example>
7934 </p>
7937 You can use a statement such as the following to get
7938 the quotes right:
7939 <example compact="compact">
7940 echo "Setting DNS domainname to \"$domainname\"."
7941 </example>
7942 </p>
7945 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
7946 for the left and right quotation marks. A grave accent
7947 (<tt>`</tt>) is not a quote character; neither is an
7948 apostrophe (<tt>'</tt>).
7949 </p>
7950 </item>
7952 <item>
7953 <p>When a daemon is stopped or restarted</p>
7956 When you stop or restart a daemon, you should issue a
7957 message identical to the startup message, except that
7958 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
7959 or <tt>Restarting</tt> respectively.
7960 </p>
7963 For example, stopping the printer daemon will look like
7964 this:
7965 <example compact="compact">
7966 Stopping printer spooler: lpd.
7967 </example>
7968 </p>
7969 </item>
7971 <item>
7972 <p>When something is executed</p>
7975 There are several examples where you have to run a
7976 program at system startup or shutdown to perform a
7977 specific task, for example, setting the system's clock
7978 using <prgn>netdate</prgn> or killing all processes
7979 when the system shuts down. Your message should look
7980 like this:
7981 <example compact="compact">
7982 Doing something very useful...done.
7983 </example>
7984 You should print the <tt>done.</tt> immediately after
7985 the job has been completed, so that the user is
7986 informed why they have to wait. You can get this
7987 behavior by saying
7988 <example compact="compact">
7989 echo -n "Doing something very useful..."
7990 do_something
7991 echo "done."
7992 </example>
7993 in your script.
7994 </p>
7995 </item>
7997 <item>
7998 <p>When the configuration is reloaded</p>
8001 When a daemon is forced to reload its configuration
8002 files you should use the following format:
8003 <example compact="compact">
8004 Reloading <var>description</var> configuration...done.
8005 </example>
8006 where <var>description</var> is the same as in the
8007 daemon starting message.
8008 </p>
8009 </item>
8010 </list>
8011 </p>
8012 </sect>
8014 <sect id="cron-jobs">
8015 <heading>Cron jobs</heading>
8018 Packages must not modify the configuration file
8019 <file>/etc/crontab</file>, and they must not modify the files in
8020 <file>/var/spool/cron/crontabs</file>.
8021 </p>
8024 If a package wants to install a job that has to be executed via
8025 cron, it should place a file named as specified
8026 in <ref id="cron-files"> into one or more of the following
8027 directories:
8028 <example compact="compact">
8029 /etc/cron.hourly
8030 /etc/cron.daily
8031 /etc/cron.weekly
8032 /etc/cron.monthly
8033 </example>
8034 As these directory names imply, the files within them are
8035 executed on an hourly, daily, weekly, or monthly basis,
8036 respectively. The exact times are listed in
8037 <file>/etc/crontab</file>.
8038 </p>
8041 All files installed in any of these directories must be
8042 scripts (e.g., shell scripts or Perl scripts) so that they
8043 can easily be modified by the local system administrator.
8044 In addition, they must be treated as configuration files.
8045 </p>
8048 If a certain job has to be executed at some other frequency or
8049 at a specific time, the package should install a file in
8050 <file>/etc/cron.d</file> with a name as specified
8051 in <ref id="cron-files">. This file uses the same syntax
8052 as <file>/etc/crontab</file> and is processed
8053 by <prgn>cron</prgn> automatically. The file must also be
8054 treated as a configuration file. (Note that entries in the
8055 <file>/etc/cron.d</file> directory are not handled by
8056 <prgn>anacron</prgn>. Thus, you should only use this
8057 directory for jobs which may be skipped if the system is not
8058 running.)
8059 </p>
8062 Unlike <file>crontab</file> files described in the IEEE Std
8063 1003.1-2008 (POSIX.1) available from
8064 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
8065 name="The Open Group">, the files in
8066 <file>/etc/cron.d</file> and the file
8067 <file>/etc/crontab</file> have seven fields; namely:
8068 <enumlist>
8069 <item>Minute [0,59]</item>
8070 <item>Hour [0,23]</item>
8071 <item>Day of the month [1,31]</item>
8072 <item>Month of the year [1,12]</item>
8073 <item>Day of the week ([0,6] with 0=Sunday)</item>
8074 <item>Username</item>
8075 <item>Command to be run</item>
8076 </enumlist>
8077 Ranges of numbers are allowed. Ranges are two numbers
8078 separated with a hyphen. The specified range is inclusive.
8079 Lists are allowed. A list is a set of numbers (or ranges)
8080 separated by commas. Step values can be used in conjunction
8081 with ranges.
8082 </p>
8085 The scripts or <tt>crontab</tt> entries in these directories should
8086 check if all necessary programs are installed before they
8087 try to execute them. Otherwise, problems will arise when a
8088 package was removed but not purged since configuration files
8089 are kept on the system in this situation.
8090 </p>
8093 Any <tt>cron</tt> daemon must provide
8094 <file>/usr/bin/crontab</file> and support normal
8095 <tt>crontab</tt> entries as specified in POSIX. The daemon
8096 must also support names for days and months, ranges, and
8097 step values. It has to support <file>/etc/crontab</file>,
8098 and correctly execute the scripts in
8099 <file>/etc/cron.d</file>. The daemon must also correctly
8100 execute scripts in
8101 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
8102 </p>
8104 <sect1 id="cron-files">
8105 <heading>Cron job file names</heading>
8108 The file name of a cron job file should normally match the
8109 name of the package from which it comes.
8110 </p>
8113 If a package supplies multiple cron job files files in the
8114 same directory, the file names should all start with the name
8115 of the package (possibly modified as described below) followed
8116 by a hyphen (<tt>-</tt>) and a suitable suffix.
8117 </p>
8120 A cron job file name must not include any period or plus
8121 characters (<tt>.</tt> or <tt>+</tt>) characters as this will
8122 cause cron to ignore the file. Underscores (<tt>_</tt>)
8123 should be used instead of <tt>.</tt> and <tt>+</tt>
8124 characters.
8125 </p>
8126 </sect1>
8127 </sect>
8129 <sect id="menus">
8130 <heading>Menus</heading>
8133 The Debian <tt>menu</tt> package provides a standard
8134 interface between packages providing applications and
8135 <em>menu programs</em> (either X window managers or
8136 text-based menu programs such as <prgn>pdmenu</prgn>).
8137 </p>
8140 All packages that provide applications that need not be
8141 passed any special command line arguments for normal
8142 operation should register a menu entry for those
8143 applications, so that users of the <tt>menu</tt> package
8144 will automatically get menu entries in their window
8145 managers, as well in shells like <tt>pdmenu</tt>.
8146 </p>
8149 Menu entries should follow the current menu policy.
8150 </p>
8153 The menu policy can be found in the <tt>menu-policy</tt>
8154 files in the <tt>debian-policy</tt> package.
8155 It is also available from the Debian web mirrors at
8156 <tt><url name="/doc/packaging-manuals/menu-policy/"
8157 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
8158 </p>
8161 Please also refer to the <em>Debian Menu System</em>
8162 documentation that comes with the <package>menu</package>
8163 package for information about how to register your
8164 applications.
8165 </p>
8166 </sect>
8168 <sect id="mime">
8169 <heading>Multimedia handlers</heading>
8172 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
8173 is a mechanism for encoding files and data streams and
8174 providing meta-information about them, in particular their
8175 type (e.g. audio or video) and format (e.g. PNG, HTML,
8176 MP3).
8177 </p>
8180 Registration of MIME type handlers allows programs like mail
8181 user agents and web browsers to invoke these handlers to
8182 view, edit or display MIME types they don't support directly.
8183 </p>
8186 Packages which provide programs to view/show/play, compose, edit or
8187 print MIME types should register them as such by placing a file in
8188 <manref name="mailcap" section="5"> format (RFC 1524) in the directory
8189 <file>/usr/lib/mime/packages/</file>. The file name should be the
8190 binary package's name.
8191 </p>
8194 The <package>mime-support</package> package provides the
8195 <prgn>update-mime</prgn> program, which integrates these
8196 registrations in the <file>/etc/mailcap</file> file, using dpkg
8197 triggers<footnote>
8198 Creating, modifying or removing a file in
8199 <file>/usr/lib/mime/packages/</file> using maintainer scripts will
8200 not activate the trigger. In that case, it can be done by calling
8201 <tt>dpkg-trigger --no-await /usr/lib/mime/packages</tt> from
8202 the maintainer script after creating, modifying, or removing
8203 the file.
8204 </footnote>.
8205 Packages using this facility <em>should not</em> depend on,
8206 recommend, or suggest <prgn>mime-support</prgn>.
8207 </p>
8208 </sect>
8210 <sect>
8211 <heading>Keyboard configuration</heading>
8214 To achieve a consistent keyboard configuration so that all
8215 applications interpret a keyboard event the same way, all
8216 programs in the Debian distribution must be configured to
8217 comply with the following guidelines.
8218 </p>
8221 The following keys must have the specified interpretations:
8223 <taglist>
8224 <tag><tt>&lt;--</tt></tag>
8225 <item>delete the character to the left of the cursor</item>
8227 <tag><tt>Delete</tt></tag>
8228 <item>delete the character to the right of the cursor</item>
8230 <tag><tt>Control+H</tt></tag>
8231 <item>emacs: the help prefix</item>
8232 </taglist>
8234 The interpretation of any keyboard events should be
8235 independent of the terminal that is used, be it a virtual
8236 console, an X terminal emulator, an rlogin/telnet session,
8237 etc.
8238 </p>
8241 The following list explains how the different programs
8242 should be set up to achieve this:
8243 </p>
8246 <list>
8247 <item>
8248 <tt>&lt;--</tt> generates <tt>KB_BackSpace</tt> in X.
8249 </item>
8251 <item>
8252 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
8253 </item>
8255 <item>
8256 X translations are set up to make
8257 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
8258 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
8259 is the vt220 escape code for the "delete character"
8260 key). This must be done by loading the X resources
8261 using <prgn>xrdb</prgn> on all local X displays, not
8262 using the application defaults, so that the
8263 translation resources used correspond to the
8264 <prgn>xmodmap</prgn> settings.
8265 </item>
8267 <item>
8268 The Linux console is configured to make
8269 <tt>&lt;--</tt> generate DEL, and <tt>Delete</tt>
8270 generate <tt>ESC [ 3 ~</tt>.
8271 </item>
8273 <item>
8274 X applications are configured so that <tt>&lt;</tt>
8275 deletes left, and <tt>Delete</tt> deletes right. Motif
8276 applications already work like this.
8277 </item>
8279 <item>
8280 Terminals should have <tt>stty erase ^?</tt> .
8281 </item>
8283 <item>
8284 The <tt>xterm</tt> terminfo entry should have <tt>ESC
8285 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
8286 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
8287 </item>
8289 <item>
8290 Emacs is programmed to map <tt>KB_Backspace</tt> or
8291 the <tt>stty erase</tt> character to
8292 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
8293 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
8294 <tt>^H</tt> to <tt>help</tt> as always.
8295 </item>
8297 <item>
8298 Other applications use the <tt>stty erase</tt>
8299 character and <tt>kdch1</tt> for the two delete keys,
8300 with ASCII DEL being "delete previous character" and
8301 <tt>kdch1</tt> being "delete character under
8302 cursor".
8303 </item>
8305 </list>
8306 </p>
8309 This will solve the problem except for the following
8310 cases:
8311 </p>
8314 <list>
8315 <item>
8316 Some terminals have a <tt>&lt;--</tt> key that cannot
8317 be made to produce anything except <tt>^H</tt>. On
8318 these terminals Emacs help will be unavailable on
8319 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
8320 character takes precedence in Emacs, and has been set
8321 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
8322 available) can be used instead.
8323 </item>
8325 <item>
8326 Some operating systems use <tt>^H</tt> for <tt>stty
8327 erase</tt>. However, modern telnet versions and all
8328 rlogin versions propagate <tt>stty</tt> settings, and
8329 almost all UNIX versions honour <tt>stty erase</tt>.
8330 Where the <tt>stty</tt> settings are not propagated
8331 correctly, things can be made to work by using
8332 <tt>stty</tt> manually.
8333 </item>
8335 <item>
8336 Some systems (including previous Debian versions) use
8337 <prgn>xmodmap</prgn> to arrange for both
8338 <tt>&lt;--</tt> and <tt>Delete</tt> to generate
8339 <tt>KB_Delete</tt>. We can change the behavior of
8340 their X clients using the same X resources that we use
8341 to do it for our own clients, or configure our clients
8342 using their resources when things are the other way
8343 around. On displays configured like this
8344 <tt>Delete</tt> will not work, but <tt>&lt;--</tt>
8345 will.
8346 </item>
8348 <item>
8349 Some operating systems have different <tt>kdch1</tt>
8350 settings in their <tt>terminfo</tt> database for
8351 <tt>xterm</tt> and others. On these systems the
8352 <tt>Delete</tt> key will not work correctly when you
8353 log in from a system conforming to our policy, but
8354 <tt>&lt;--</tt> will.
8355 </item>
8356 </list>
8357 </p>
8358 </sect>
8360 <sect>
8361 <heading>Environment variables</heading>
8364 A program must not depend on environment variables to get
8365 reasonable defaults. (That's because these environment
8366 variables would have to be set in a system-wide
8367 configuration file like <file>/etc/profile</file>, which is not
8368 supported by all shells.)
8369 </p>
8372 If a program usually depends on environment variables for its
8373 configuration, the program should be changed to fall back to
8374 a reasonable default configuration if these environment
8375 variables are not present. If this cannot be done easily
8376 (e.g., if the source code of a non-free program is not
8377 available), the program must be replaced by a small
8378 "wrapper" shell script which sets the environment variables
8379 if they are not already defined, and calls the original program.
8380 </p>
8383 Here is an example of a wrapper script for this purpose:
8385 <example compact="compact">
8386 #!/bin/sh
8387 BAR=${BAR:-/var/lib/fubar}
8388 export BAR
8389 exec /usr/lib/foo/foo "$@"
8390 </example>
8391 </p>
8394 Furthermore, as <file>/etc/profile</file> is a configuration
8395 file of the <prgn>base-files</prgn> package, other packages must
8396 not put any environment variables or other commands into that
8397 file.
8398 </p>
8399 </sect>
8401 <sect id="doc-base">
8402 <heading>Registering Documents using doc-base</heading>
8405 The <package>doc-base</package> package implements a
8406 flexible mechanism for handling and presenting
8407 documentation. The recommended practice is for every Debian
8408 package that provides online documentation (other than just
8409 manual pages) to register these documents with
8410 <package>doc-base</package> by installing a
8411 <package>doc-base</package> control file in
8412 <file>/usr/share/doc-base/</file>.
8413 </p>
8415 Please refer to the documentation that comes with the
8416 <package>doc-base</package> package for information and
8417 details.
8418 </p>
8419 </sect>
8421 <sect id="alternateinit">
8422 <heading>Alternate init systems</heading>
8424 A number of other init systems are available now in Debian that
8425 can be used in place of <package>sysvinit</package>. Alternative
8426 init implementations must support running SysV init scripts as
8427 described at <ref id="sysvinit"> for compatibility.
8428 </p>
8430 Packages may integrate with these replacement init systems by
8431 providing implementation-specific configuration information about
8432 how and when to start a service or in what order to run certain
8433 tasks at boot time. However, any package integrating with other
8434 init systems must also be backwards-compatible with
8435 <package>sysvinit</package> by providing a SysV-style init script
8436 with the same name as and equivalent functionality to any
8437 init-specific job, as this is the only start-up configuration
8438 method guaranteed to be supported by all init implementations. An
8439 exception to this rule is scripts or jobs provided by the init
8440 implementation itself; such jobs may be required for an
8441 implementation-specific equivalent of the <file>/etc/rcS.d/</file>
8442 scripts and may not have a one-to-one correspondence with the init
8443 scripts.
8444 </p>
8445 <sect1 id="upstart">
8446 <heading>Event-based boot with upstart</heading>
8449 Packages may integrate with the <prgn>upstart</prgn> event-based
8450 boot system by installing job files in the
8451 <file>/etc/init</file> directory. SysV init scripts for which
8452 an equivalent upstart job is available must query the output of
8453 the command <prgn>initctl version</prgn> for the string
8454 <tt>upstart</tt> and avoid running in favor of the native
8455 upstart job, using a test such as this:
8456 <example compact="compact">
8457 if [ "$1" = start ] && which initctl >/dev/null && initctl version | grep -q upstart
8458 then
8459 exit 1
8461 </example>
8462 </p>
8464 Because packages shipping upstart jobs may be installed on
8465 systems that are not using upstart, maintainer scripts must
8466 still use the common <prgn>update-rc.d</prgn> and
8467 <prgn>invoke-rc.d</prgn> interfaces for configuring runlevels
8468 and for starting and stopping services. These maintainer
8469 scripts must not call the upstart <prgn>start</prgn>,
8470 <prgn>restart</prgn>, <prgn>reload</prgn>, or <prgn>stop</prgn>
8471 interfaces directly. Instead, implementations of
8472 <prgn>invoke-rc.d</prgn> must detect when upstart is running and
8473 when an upstart job with the same name as an init script is
8474 present, and perform the requested action using the upstart job
8475 instead of the init script.
8476 </p>
8478 Dependency-based boot managers for SysV init scripts, such as
8479 <prgn>startpar</prgn>, may avoid running a given init script
8480 entirely when an equivalent upstart job is present, to avoid
8481 unnecessary forking of no-op init scripts. In this case, the
8482 boot manager should integrate with upstart to detect when the
8483 upstart job in question is started or stopped to know when the
8484 dependency has been satisfied.
8485 </p>
8486 </sect1>
8487 </sect>
8489 </chapt>
8492 <chapt id="files">
8493 <heading>Files</heading>
8495 <sect id="binaries">
8496 <heading>Binaries</heading>
8499 Two different packages must not install programs with
8500 different functionality but with the same filenames. (The
8501 case of two programs having the same functionality but
8502 different implementations is handled via "alternatives" or
8503 the "Conflicts" mechanism. See <ref id="maintscripts"> and
8504 <ref id="conflicts"> respectively.) If this case happens,
8505 one of the programs must be renamed. The maintainers should
8506 report this to the <tt>debian-devel</tt> mailing list and
8507 try to find a consensus about which program will have to be
8508 renamed. If a consensus cannot be reached, <em>both</em>
8509 programs must be renamed.
8510 </p>
8512 Binary executables must not be statically linked with the GNU C
8513 library, since this prevents the binary from benefiting from
8514 fixes and improvements to the C library without being rebuilt
8515 and complicates security updates. This requirement may be
8516 relaxed for binary executables whose intended purpose is to
8517 diagnose and fix the system in situations where the GNU C
8518 library may not be usable (such as system recovery shells or
8519 utilities like ldconfig) or for binary executables where the
8520 security benefits of static linking outweigh the drawbacks.
8521 </p>
8523 By default, when a package is being built, any binaries
8524 created should include debugging information, as well as
8525 being compiled with optimization. You should also turn on
8526 as many reasonable compilation warnings as possible; this
8527 makes life easier for porters, who can then look at build
8528 logs for possible problems. For the C programming language,
8529 this means the following compilation parameters should be
8530 used:
8531 <example compact="compact">
8532 CC = gcc
8533 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
8534 LDFLAGS = # none
8535 INSTALL = install -s # (or use strip on the files in debian/tmp)
8536 </example>
8537 </p>
8540 Note that by default all installed binaries should be stripped,
8541 either by using the <tt>-s</tt> flag to
8542 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
8543 the binaries after they have been copied into
8544 <file>debian/tmp</file> but before the tree is made into a
8545 package.
8546 </p>
8549 Although binaries in the build tree should be compiled with
8550 debugging information by default, it can often be difficult to
8551 debug programs if they are also subjected to compiler
8552 optimization. For this reason, it is recommended to support the
8553 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
8554 (see <ref id="debianrules-options">). This variable can contain
8555 several flags to change how a package is compiled and built.
8556 </p>
8559 It is up to the package maintainer to decide what
8560 compilation options are best for the package. Certain
8561 binaries (such as computationally-intensive programs) will
8562 function better with certain flags (<tt>-O3</tt>, for
8563 example); feel free to use them. Please use good judgment
8564 here. Don't use flags for the sake of it; only use them
8565 if there is good reason to do so. Feel free to override
8566 the upstream author's ideas about which compilation
8567 options are best: they are often inappropriate for our
8568 environment.
8569 </p>
8570 </sect>
8573 <sect id="libraries">
8574 <heading>Libraries</heading>
8577 If the package is <strong>architecture: any</strong>, then
8578 the shared library compilation and linking flags must have
8579 <tt>-fPIC</tt>, or the package shall not build on some of
8580 the supported architectures<footnote>
8582 If you are using GCC, <tt>-fPIC</tt> produces code with
8583 relocatable position independent code, which is required for
8584 most architectures to create a shared library, with i386 and
8585 perhaps some others where non position independent code is
8586 permitted in a shared library.
8587 </p>
8589 Position independent code may have a performance penalty,
8590 especially on <tt>i386</tt>. However, in most cases the
8591 speed penalty must be measured against the memory wasted on
8592 the few architectures where non position independent code is
8593 even possible.
8594 </p>
8595 </footnote>. Any exception to this rule must be discussed on
8596 the mailing list <em>debian-devel@lists.debian.org</em>, and
8597 a rough consensus obtained. The reasons for not compiling
8598 with <tt>-fPIC</tt> flag must be recorded in the file
8599 <tt>README.Debian</tt>, and care must be taken to either
8600 restrict the architecture or arrange for <tt>-fPIC</tt> to
8601 be used on architectures where it is required.<footnote>
8603 Some of the reasons why this might be required is if the
8604 library contains hand crafted assembly code that is not
8605 relocatable, the speed penalty is excessive for compute
8606 intensive libs, and similar reasons.
8607 </p>
8608 </footnote>
8609 </p>
8611 As to the static libraries, the common case is not to have
8612 relocatable code, since there is no benefit, unless in specific
8613 cases; therefore the static version must not be compiled
8614 with the <tt>-fPIC</tt> flag. Any exception to this rule
8615 should be discussed on the mailing list
8616 <em>debian-devel@lists.debian.org</em>, and the reasons for
8617 compiling with the <tt>-fPIC</tt> flag must be recorded in
8618 the file <tt>README.Debian</tt>. <footnote>
8620 Some of the reasons for linking static libraries with
8621 the <tt>-fPIC</tt> flag are if, for example, one needs a
8622 Perl API for a library that is under rapid development,
8623 and has an unstable API, so shared libraries are
8624 pointless at this phase of the library's development. In
8625 that case, since Perl needs a library with relocatable
8626 code, it may make sense to create a static library with
8627 relocatable code. Another reason cited is if you are
8628 distilling various libraries into a common shared
8629 library, like <tt>mklibs</tt> does in the Debian
8630 installer project.
8631 </p>
8632 </footnote>
8633 </p>
8635 In other words, if both a shared and a static library is
8636 being built, each source unit (<tt>*.c</tt>, for example,
8637 for C files) will need to be compiled twice, for the normal
8638 case.
8639 </p>
8642 Libraries should be built with threading support and to be
8643 thread-safe if the library supports this.
8644 </p>
8647 Although not enforced by the build tools, shared libraries
8648 must be linked against all libraries that they use symbols from
8649 in the same way that binaries are. This ensures the correct
8650 functioning of the <qref id="sharedlibs-symbols">symbols</qref>
8651 and <qref id="sharedlibs-shlibdeps">shlibs</qref>
8652 systems and guarantees that all libraries can be safely opened
8653 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
8654 option <tt>-Wl,-z,defs</tt> when building a shared library.
8655 Since this option enforces symbol resolution at build time,
8656 a missing library reference will be caught early as a fatal
8657 build error.
8658 </p>
8661 All installed shared libraries should be stripped with
8662 <example compact="compact">
8663 strip --strip-unneeded <var>your-lib</var>
8664 </example>
8665 (The option <tt>--strip-unneeded</tt> makes
8666 <prgn>strip</prgn> remove only the symbols which aren't
8667 needed for relocation processing.) Shared libraries can
8668 function perfectly well when stripped, since the symbols for
8669 dynamic linking are in a separate part of the ELF object
8670 file.<footnote>
8671 You might also want to use the options
8672 <tt>--remove-section=.comment</tt> and
8673 <tt>--remove-section=.note</tt> on both shared libraries
8674 and executables, and <tt>--strip-debug</tt> on static
8675 libraries.
8676 </footnote>
8677 </p>
8680 Note that under some circumstances it may be useful to
8681 install a shared library unstripped, for example when
8682 building a separate package to support debugging.
8683 </p>
8686 Shared object files (often <file>.so</file> files) that are not
8687 public libraries, that is, they are not meant to be linked
8688 to by third party executables (binaries of other packages),
8689 should be installed in subdirectories of the
8690 <file>/usr/lib</file> directory. Such files are exempt from the
8691 rules that govern ordinary shared libraries, except that
8692 they must not be installed executable and should be
8693 stripped.<footnote>
8694 A common example are the so-called "plug-ins",
8695 internal shared objects that are dynamically loaded by
8696 programs using <manref name="dlopen" section="3">.
8697 </footnote>
8698 </p>
8701 Packages that use <prgn>libtool</prgn> to create and install
8702 their shared libraries install a file containing additional
8703 metadata (ending in <file>.la</file>) alongside the library.
8704 For public libraries intended for use by other packages, these
8705 files normally should not be included in the Debian package,
8706 since the information they include is not necessary to link with
8707 the shared library on Debian and can add unnecessary additional
8708 dependencies to other programs or libraries.<footnote>
8709 These files store, among other things, all libraries on which
8710 that shared library depends. Unfortunately, if
8711 the <file>.la</file> file is present and contains that
8712 dependency information, using <prgn>libtool</prgn> when
8713 linking against that library will cause the resulting program
8714 or library to be linked against those dependencies as well,
8715 even if this is unnecessary. This can create unneeded
8716 dependencies on shared library packages that would otherwise
8717 be hidden behind the library ABI, and can make library
8718 transitions to new SONAMEs unnecessarily complicated and
8719 difficult to manage.
8720 </footnote>
8721 If the <file>.la</file> file is required for that library (if,
8722 for instance, it's loaded via <tt>libltdl</tt> in a way that
8723 requires that meta-information), the <tt>dependency_libs</tt>
8724 setting in the <file>.la</file> file should normally be set to
8725 the empty string. If the shared library development package has
8726 historically included the <file>.la</file>, it must be retained
8727 in the development package (with <tt>dependency_libs</tt>
8728 emptied) until all libraries that depend on it have removed or
8729 emptied <tt>dependency_libs</tt> in their <file>.la</file>
8730 files to prevent linking with those other libraries
8731 using <prgn>libtool</prgn> from failing.
8732 </p>
8735 If the <file>.la</file> must be included, it should be included
8736 in the development (<tt>-dev</tt>) package, unless the library
8737 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
8738 library. If it is intended for use with <tt>libltdl</tt>,
8739 the <file>.la</file> files must go in the run-time library
8740 package.
8741 </p>
8744 These requirements for handling of <file>.la</file> files do not
8745 apply to loadable modules or libraries not installed in
8746 directories searched by default by the dynamic linker. Packages
8747 installing loadable modules will frequently need to install
8748 the <file>.la</file> files alongside the modules so that they
8749 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
8750 does not need to be modified for libraries or modules that are
8751 not installed in directories searched by the dynamic linker by
8752 default and not intended for use by other packages.
8753 </p>
8756 You must make sure that you use only released versions of
8757 shared libraries to build your packages; otherwise other
8758 users will not be able to run your binaries
8759 properly. Producing source packages that depend on
8760 unreleased compilers is also usually a bad
8761 idea.
8762 </p>
8763 </sect>
8766 <sect>
8767 <heading>Shared libraries</heading>
8769 This section has moved to <ref id="sharedlibs">.
8770 </p>
8771 </sect>
8774 <sect id="scripts">
8775 <heading>Scripts</heading>
8778 All command scripts, including the package maintainer
8779 scripts inside the package and used by <prgn>dpkg</prgn>,
8780 should have a <tt>#!</tt> line naming the shell to be used
8781 to interpret them.
8782 </p>
8785 In the case of Perl scripts this should be
8786 <tt>#!/usr/bin/perl</tt>.
8787 </p>
8790 When scripts are installed into a directory in the system
8791 PATH, the script name should not include an extension such
8792 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
8793 language currently used to implement it.
8794 </p>
8796 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
8797 <file>init.d</file> scripts should almost certainly start
8798 with <tt>set -e</tt> so that errors are detected.
8799 <file>init.d</file> scripts are something of a special case, due
8800 to how frequently they need to call commands that are allowed to
8801 fail, and it may instead be easier to check the exit status of
8802 commands directly. See <ref id="writing-init"> for more
8803 information about writing <file>init.d</file> scripts.
8804 </p>
8806 Every script should use <tt>set -e</tt> or check the exit status
8807 of <em>every</em> command.
8808 </p>
8810 Scripts may assume that <file>/bin/sh</file> implements the
8811 SUSv3 Shell Command Language<footnote>
8812 Single UNIX Specification, version 3, which is also IEEE
8813 1003.1-2004 (POSIX), and is available on the World Wide Web
8814 from <url id="http://www.unix.org/version3/online.html"
8815 name="The Open Group"> after free
8816 registration.</footnote>
8817 plus the following additional features not mandated by
8818 SUSv3:<footnote>
8819 These features are in widespread use in the Linux community
8820 and are implemented in all of bash, dash, and ksh, the most
8821 common shells users may wish to use as <file>/bin/sh</file>.
8822 </footnote>
8823 <list>
8824 <item><tt>echo -n</tt>, if implemented as a shell built-in,
8825 must not generate a newline.</item>
8826 <item><tt>test</tt>, if implemented as a shell built-in, must
8827 support <tt>-a</tt> and <tt>-o</tt> as binary logical
8828 operators.</item>
8829 <item><tt>local</tt> to create a scoped variable must be
8830 supported, including listing multiple variables in a single
8831 local command and assigning a value to a variable at the
8832 same time as localizing it. <tt>local</tt> may or
8833 may not preserve the variable value from an outer scope if
8834 no assignment is present. Uses such as:
8835 <example compact>
8836 fname () {
8837 local a b c=delta d
8838 # ... use a, b, c, d ...
8840 </example>
8841 must be supported and must set the value of <tt>c</tt> to
8842 <tt>delta</tt>.
8843 </item>
8844 <item>The XSI extension to <prgn>kill</prgn> allowing <tt>kill
8845 -<var>signal</var></tt>, where <var>signal</var> is either
8846 the name of a signal or one of the numeric signals listed in
8847 the XSI extension (0, 1, 2, 3, 6, 9, 14, and 15), must be
8848 supported if <prgn>kill</prgn> is implemented as a shell
8849 built-in.
8850 </item>
8851 <item>The XSI extension to <prgn>trap</prgn> allowing numeric
8852 signals must be supported. In addition to the signal
8853 numbers listed in the extension, which are the same as for
8854 <prgn>kill</prgn> above, 13 (SIGPIPE) must be allowed.
8855 </item>
8856 </list>
8857 If a shell script requires non-SUSv3 features from the shell
8858 interpreter other than those listed above, the appropriate shell
8859 must be specified in the first line of the script (e.g.,
8860 <tt>#!/bin/bash</tt>) and the package must depend on the package
8861 providing the shell (unless the shell package is marked
8862 "Essential", as in the case of <prgn>bash</prgn>).
8863 </p>
8866 You may wish to restrict your script to SUSv3 features plus the
8867 above set when possible so that it may use <file>/bin/sh</file>
8868 as its interpreter. Checking your script
8869 with <prgn>checkbashisms</prgn> from
8870 the <package>devscripts</package> package or running your script
8871 with an alternate shell such as <prgn>posh</prgn> may help
8872 uncover violations of the above requirements. If in doubt
8873 whether a script complies with these requirements,
8874 use <file>/bin/bash</file>.
8875 </p>
8878 Perl scripts should check for errors when making any
8879 system calls, including <tt>open</tt>, <tt>print</tt>,
8880 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
8881 </p>
8884 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
8885 scripting languages. See <em>Csh Programming Considered
8886 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
8887 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
8888 If an upstream package comes with <prgn>csh</prgn> scripts
8889 then you must make sure that they start with
8890 <tt>#!/bin/csh</tt> and make your package depend on the
8891 <prgn>c-shell</prgn> virtual package.
8892 </p>
8895 Any scripts which create files in world-writeable
8896 directories (e.g., in <file>/tmp</file>) must use a
8897 mechanism which will fail atomically if a file with the same
8898 name already exists.
8899 </p>
8902 The Debian base system provides the <prgn>tempfile</prgn>
8903 and <prgn>mktemp</prgn> utilities for use by scripts for
8904 this purpose.
8905 </p>
8906 </sect>
8909 <sect>
8910 <heading>Symbolic links</heading>
8913 In general, symbolic links within a top-level directory should
8914 be relative, and symbolic links pointing from one top-level
8915 directory to or into another should be absolute. (A top-level
8916 directory is a sub-directory of the root
8917 directory <file>/</file>.) For example, a symbolic link
8918 from <file>/usr/lib/foo</file> to <file>/usr/share/bar</file>
8919 should be relative (<file>../share/bar</file>), but a symbolic
8920 link from <file>/var/run</file> to <file>/run</file> should be
8921 absolute.<footnote>
8922 This is necessary to allow top-level directories to be
8923 symlinks. If linking <file>/var/run</file>
8924 to <file>/run</file> were done with the relative symbolic
8925 link <file>../run</file>, but <file>/var</file> were a
8926 symbolic link to <file>/srv/disk1</file>, the symbolic link
8927 would point to <file>/srv/run</file> rather than the intended
8928 target.
8929 </footnote>
8930 Symbolic links must not traverse above the root directory.
8931 </p>
8934 In addition, symbolic links should be specified as short as
8935 possible, i.e., link targets like <file>foo/../bar</file> are
8936 deprecated.
8937 </p>
8940 Note that when creating a relative link using
8941 <prgn>ln</prgn> it is not necessary for the target of the
8942 link to exist relative to the working directory you're
8943 running <prgn>ln</prgn> from, nor is it necessary to change
8944 directory to the directory where the link is to be made.
8945 Simply include the string that should appear as the target
8946 of the link (this will be a pathname relative to the
8947 directory in which the link resides) as the first argument
8948 to <prgn>ln</prgn>.
8949 </p>
8952 For example, in your <prgn>Makefile</prgn> or
8953 <file>debian/rules</file>, you can do things like:
8954 <example compact="compact">
8955 ln -fs gcc $(prefix)/bin/cc
8956 ln -fs gcc debian/tmp/usr/bin/cc
8957 ln -fs ../sbin/sendmail $(prefix)/bin/runq
8958 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
8959 </example>
8960 </p>
8963 A symbolic link pointing to a compressed file (in the sense
8964 that it is meant to be uncompressed with <prgn>unzip</prgn>
8965 or <prgn>zless</prgn> etc.) should always
8966 have the same file extension as the referenced file. (For
8967 example, if a file <file>foo.gz</file> is referenced by a
8968 symbolic link, the filename of the link has to end with
8969 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
8970 </p>
8971 </sect>
8973 <sect>
8974 <heading>Device files</heading>
8977 Packages must not include device files or named pipes in the
8978 package file tree.
8979 </p>
8982 If a package needs any special device files that are not
8983 included in the base system, it must call
8984 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
8985 after notifying the user<footnote>
8986 This notification could be done via a (low-priority)
8987 debconf message, or an echo (printf) statement.
8988 </footnote>.
8989 </p>
8992 Packages must not remove any device files in the
8993 <prgn>postrm</prgn> or any other script. This is left to the
8994 system administrator.
8995 </p>
8998 Debian uses the serial devices
8999 <file>/dev/ttyS*</file>. Programs using the old
9000 <file>/dev/cu*</file> devices should be changed to use
9001 <file>/dev/ttyS*</file>.
9002 </p>
9005 Named pipes needed by the package must be created in
9006 the <prgn>postinst</prgn> script<footnote>
9007 It's better to use <prgn>mkfifo</prgn> rather
9008 than <prgn>mknod</prgn> to create named pipes so that
9009 automated checks for packages incorrectly creating device
9010 files with <prgn>mknod</prgn> won't have false positives.
9011 </footnote> and removed in
9012 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
9013 appropriate.
9014 </p>
9015 </sect>
9017 <sect id="config-files">
9018 <heading>Configuration files</heading>
9020 <sect1>
9021 <heading>Definitions</heading>
9024 <taglist>
9025 <tag>configuration file</tag>
9026 <item>
9027 A file that affects the operation of a program, or
9028 provides site- or host-specific information, or
9029 otherwise customizes the behavior of a program.
9030 Typically, configuration files are intended to be
9031 modified by the system administrator (if needed or
9032 desired) to conform to local policy or to provide
9033 more useful site-specific behavior.
9034 </item>
9036 <tag><tt>conffile</tt></tag>
9037 <item>
9038 A file listed in a package's <tt>conffiles</tt>
9039 file, and is treated specially by <prgn>dpkg</prgn>
9040 (see <ref id="configdetails">).
9041 </item>
9042 </taglist>
9043 </p>
9046 The distinction between these two is important; they are
9047 not interchangeable concepts. Almost all
9048 <tt>conffile</tt>s are configuration files, but many
9049 configuration files are not <tt>conffiles</tt>.
9050 </p>
9053 As noted elsewhere, <file>/etc/init.d</file> scripts,
9054 <file>/etc/default</file> files, scripts installed in
9055 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
9056 configuration installed in <file>/etc/cron.d</file> must be
9057 treated as configuration files. In general, any script that
9058 embeds configuration information is de-facto a configuration
9059 file and should be treated as such.
9060 </p>
9061 </sect1>
9063 <sect1>
9064 <heading>Location</heading>
9067 Any configuration files created or used by your package
9068 must reside in <file>/etc</file>. If there are several,
9069 consider creating a subdirectory of <file>/etc</file>
9070 named after your package.
9071 </p>
9074 If your package creates or uses configuration files
9075 outside of <file>/etc</file>, and it is not feasible to modify
9076 the package to use <file>/etc</file> directly, put the files
9077 in <file>/etc</file> and create symbolic links to those files
9078 from the location that the package requires.
9079 </p>
9080 </sect1>
9082 <sect1>
9083 <heading>Behavior</heading>
9086 Configuration file handling must conform to the following
9087 behavior:
9088 <list compact="compact">
9089 <item>
9090 local changes must be preserved during a package
9091 upgrade, and
9092 </item>
9093 <item>
9094 configuration files must be preserved when the
9095 package is removed, and only deleted when the
9096 package is purged.
9097 </item>
9098 </list>
9099 Obsolete configuration files without local changes should be
9100 removed by the package during upgrade.<footnote>
9101 The <prgn>dpkg-maintscript-helper</prgn> tool, available from the
9102 <package>dpkg</package> package, can help for this task.</footnote>
9103 </p>
9106 The easy way to achieve this behavior is to make the
9107 configuration file a <tt>conffile</tt>. This is
9108 appropriate only if it is possible to distribute a default
9109 version that will work for most installations, although
9110 some system administrators may choose to modify it. This
9111 implies that the default version will be part of the
9112 package distribution, and must not be modified by the
9113 maintainer scripts during installation (or at any other
9114 time).
9115 </p>
9118 In order to ensure that local changes are preserved
9119 correctly, no package may contain or make hard links to
9120 conffiles.<footnote>
9121 Rationale: There are two problems with hard links.
9122 The first is that some editors break the link while
9123 editing one of the files, so that the two files may
9124 unwittingly become unlinked and different. The second
9125 is that <prgn>dpkg</prgn> might break the hard link
9126 while upgrading <tt>conffile</tt>s.
9127 </footnote>
9128 </p>
9131 The other way to do it is via the maintainer scripts. In
9132 this case, the configuration file must not be listed as a
9133 <tt>conffile</tt> and must not be part of the package
9134 distribution. If the existence of a file is required for
9135 the package to be sensibly configured it is the
9136 responsibility of the package maintainer to provide
9137 maintainer scripts which correctly create, update and
9138 maintain the file and remove it on purge. (See <ref
9139 id="maintainerscripts"> for more information.) These
9140 scripts must be idempotent (i.e., must work correctly if
9141 <prgn>dpkg</prgn> needs to re-run them due to errors
9142 during installation or removal), must cope with all the
9143 variety of ways <prgn>dpkg</prgn> can call maintainer
9144 scripts, must not overwrite or otherwise mangle the user's
9145 configuration without asking, must not ask unnecessary
9146 questions (particularly during upgrades), and must
9147 otherwise be good citizens.
9148 </p>
9151 The scripts are not required to configure every possible
9152 option for the package, but only those necessary to get
9153 the package running on a given system. Ideally the
9154 sysadmin should not have to do any configuration other
9155 than that done (semi-)automatically by the
9156 <prgn>postinst</prgn> script.
9157 </p>
9160 A common practice is to create a script called
9161 <file><var>package</var>-configure</file> and have the
9162 package's <prgn>postinst</prgn> call it if and only if the
9163 configuration file does not already exist. In certain
9164 cases it is useful for there to be an example or template
9165 file which the maintainer scripts use. Such files should
9166 be in <file>/usr/share/<var>package</var></file> or
9167 <file>/usr/lib/<var>package</var></file> (depending on whether
9168 they are architecture-independent or not). There should
9169 be symbolic links to them from
9170 <file>/usr/share/doc/<var>package</var>/examples</file> if
9171 they are examples, and should be perfectly ordinary
9172 <prgn>dpkg</prgn>-handled files (<em>not</em>
9173 configuration files).
9174 </p>
9177 These two styles of configuration file handling must
9178 not be mixed, for that way lies madness:
9179 <prgn>dpkg</prgn> will ask about overwriting the file
9180 every time the package is upgraded.
9181 </p>
9182 </sect1>
9184 <sect1>
9185 <heading>Sharing configuration files</heading>
9188 If two or more packages use the same configuration file
9189 and it is reasonable for both to be installed at the same
9190 time, one of these packages must be defined as
9191 <em>owner</em> of the configuration file, i.e., it will be
9192 the package which handles that file as a configuration
9193 file. Other packages that use the configuration file must
9194 depend on the owning package if they require the
9195 configuration file to operate. If the other package will
9196 use the configuration file if present, but is capable of
9197 operating without it, no dependency need be declared.
9198 </p>
9201 If it is desirable for two or more related packages to
9202 share a configuration file <em>and</em> for all of the
9203 related packages to be able to modify that configuration
9204 file, then the following should be done:
9205 <enumlist compact="compact">
9206 <item>
9207 One of the related packages (the "owning" package)
9208 will manage the configuration file with maintainer
9209 scripts as described in the previous section.
9210 </item>
9211 <item>
9212 The owning package should also provide a program
9213 that the other packages may use to modify the
9214 configuration file.
9215 </item>
9216 <item>
9217 The related packages must use the provided program
9218 to make any desired modifications to the
9219 configuration file. They should either depend on
9220 the core package to guarantee that the configuration
9221 modifier program is available or accept gracefully
9222 that they cannot modify the configuration file if it
9223 is not. (This is in addition to the fact that the
9224 configuration file may not even be present in the
9225 latter scenario.)
9226 </item>
9227 </enumlist>
9228 </p>
9231 Sometimes it's appropriate to create a new package which
9232 provides the basic infrastructure for the other packages
9233 and which manages the shared configuration files. (The
9234 <tt>sgml-base</tt> package is a good example.)
9235 </p>
9238 If the configuration file cannot be shared as described above,
9239 the packages must be marked as conflicting with each other.
9240 Two packages that specify the same file as
9241 a <tt>conffile</tt> must conflict. This is an instance of the
9242 general rule about not sharing files. Neither alternatives
9243 nor diversions are likely to be appropriate in this case; in
9244 particular, <prgn>dpkg</prgn> does not handle diverted
9245 <tt>conffile</tt>s well.
9246 </p>
9249 When two packages both declare the same <tt>conffile</tt>, they
9250 may see left-over configuration files from each other even
9251 though they conflict with each other. If a user removes
9252 (without purging) one of the packages and installs the other,
9253 the new package will take over the <tt>conffile</tt> from the
9254 old package. If the file was modified by the user, it will be
9255 treated the same as any other locally
9256 modified <tt>conffile</tt> during an upgrade.
9257 </p>
9260 The maintainer scripts must not alter a <tt>conffile</tt>
9261 of <em>any</em> package, including the one the scripts
9262 belong to.
9263 </p>
9264 </sect1>
9266 <sect1>
9267 <heading>User configuration files ("dotfiles")</heading>
9270 The files in <file>/etc/skel</file> will automatically be
9271 copied into new user accounts by <prgn>adduser</prgn>.
9272 No other program should reference the files in
9273 <file>/etc/skel</file>.
9274 </p>
9277 Therefore, if a program needs a dotfile to exist in
9278 advance in <file>$HOME</file> to work sensibly, that dotfile
9279 should be installed in <file>/etc/skel</file> and treated as a
9280 configuration file.
9281 </p>
9284 However, programs that require dotfiles in order to
9285 operate sensibly are a bad thing, unless they do create
9286 the dotfiles themselves automatically.
9287 </p>
9290 Furthermore, programs should be configured by the Debian
9291 default installation to behave as closely to the upstream
9292 default behavior as possible.
9293 </p>
9296 Therefore, if a program in a Debian package needs to be
9297 configured in some way in order to operate sensibly, that
9298 should be done using a site-wide configuration file placed
9299 in <file>/etc</file>. Only if the program doesn't support a
9300 site-wide default configuration and the package maintainer
9301 doesn't have time to add it may a default per-user file be
9302 placed in <file>/etc/skel</file>.
9303 </p>
9306 <file>/etc/skel</file> should be as empty as we can make it.
9307 This is particularly true because there is no easy (or
9308 necessarily desirable) mechanism for ensuring that the
9309 appropriate dotfiles are copied into the accounts of
9310 existing users when a package is installed.
9311 </p>
9312 </sect1>
9313 </sect>
9315 <sect>
9316 <heading>Log files</heading>
9318 Log files should usually be named
9319 <file>/var/log/<var>package</var>.log</file>. If you have many
9320 log files, or need a separate directory for permission
9321 reasons (<file>/var/log</file> is writable only by
9322 <file>root</file>), you should usually create a directory named
9323 <file>/var/log/<var>package</var></file> and place your log
9324 files there.
9325 </p>
9328 Log files must be rotated occasionally so that they don't grow
9329 indefinitely. The best way to do this is to install a log
9330 rotation configuration file in the
9331 directory <file>/etc/logrotate.d</file>, normally
9332 named <file>/etc/logrotate.d/<var>package</var></file>, and use
9333 the facilities provided by <prgn>logrotate</prgn>.
9334 <footnote>
9336 The traditional approach to log files has been to set up
9337 <em>ad hoc</em> log rotation schemes using simple shell
9338 scripts and cron. While this approach is highly
9339 customizable, it requires quite a lot of sysadmin work.
9340 Even though the original Debian system helped a little
9341 by automatically installing a system which can be used
9342 as a template, this was deemed not enough.
9343 </p>
9346 The use of <prgn>logrotate</prgn>, a program developed
9347 by Red Hat, is better, as it centralizes log management.
9348 It has both a configuration file
9349 (<file>/etc/logrotate.conf</file>) and a directory where
9350 packages can drop their individual log rotation
9351 configurations (<file>/etc/logrotate.d</file>).
9352 </p>
9353 </footnote>
9354 Here is a good example for a logrotate config
9355 file (for more information see <manref name="logrotate"
9356 section="8">):
9357 <example compact="compact">
9358 /var/log/foo/*.log {
9359 rotate 12
9360 weekly
9361 compress
9362 missingok
9363 postrotate
9364 start-stop-daemon -K -p /var/run/foo.pid -s HUP -x /usr/sbin/foo -q
9365 endscript
9367 </example>
9368 This rotates all files under <file>/var/log/foo</file>, saves 12
9369 compressed generations, and tells the daemon to reopen its log
9370 files after the log rotation. It skips this log rotation
9371 (via <tt>missingok</tt>) if no such log file is present, which
9372 avoids errors if the package is removed but not purged.
9373 </p>
9376 Log files should be removed when the package is
9377 purged (but not when it is only removed). This should be
9378 done by the <prgn>postrm</prgn> script when it is called
9379 with the argument <tt>purge</tt> (see <ref
9380 id="removedetails">).
9381 </p>
9382 </sect>
9384 <sect id="permissions-owners">
9385 <heading>Permissions and owners</heading>
9388 The rules in this section are guidelines for general use.
9389 If necessary you may deviate from the details below.
9390 However, if you do so you must make sure that what is done
9391 is secure and you should try to be as consistent as possible
9392 with the rest of the system. You should probably also
9393 discuss it on <prgn>debian-devel</prgn> first.
9394 </p>
9397 Files should be owned by <tt>root:root</tt>, and made
9398 writable only by the owner and universally readable (and
9399 executable, if appropriate), that is mode 644 or 755.
9400 </p>
9403 Directories should be mode 755 or (for group-writability)
9404 mode 2775. The ownership of the directory should be
9405 consistent with its mode: if a directory is mode 2775, it
9406 should be owned by the group that needs write access to
9407 it.<footnote>
9409 When a package is upgraded, and the owner or permissions
9410 of a file included in the package has changed, dpkg
9411 arranges for the ownership and permissions to be
9412 correctly set upon installation. However, this does not
9413 extend to directories; the permissions and ownership of
9414 directories already on the system does not change on
9415 install or upgrade of packages. This makes sense, since
9416 otherwise common directories like <tt>/usr</tt> would
9417 always be in flux. To correctly change permissions of a
9418 directory the package owns, explicit action is required,
9419 usually in the <tt>postinst</tt> script. Care must be
9420 taken to handle downgrades as well, in that case.
9421 </p>
9422 </footnote>
9423 </p>
9426 Control information files should be owned by <tt>root:root</tt>
9427 and either mode 644 (for most files) or mode 755 (for
9428 executables such as <qref id="maintscripts">maintainer
9429 scripts</qref>).
9430 </p>
9433 Setuid and setgid executables should be mode 4755 or 2755
9434 respectively, and owned by the appropriate user or group.
9435 They should not be made unreadable (modes like 4711 or
9436 2711 or even 4111); doing so achieves no extra security,
9437 because anyone can find the binary in the freely available
9438 Debian package; it is merely inconvenient. For the same
9439 reason you should not restrict read or execute permissions
9440 on non-set-id executables.
9441 </p>
9444 Some setuid programs need to be restricted to particular
9445 sets of users, using file permissions. In this case they
9446 should be owned by the uid to which they are set-id, and by
9447 the group which should be allowed to execute them. They
9448 should have mode 4754; again there is no point in making
9449 them unreadable to those users who must not be allowed to
9450 execute them.
9451 </p>
9454 It is possible to arrange that the system administrator can
9455 reconfigure the package to correspond to their local
9456 security policy by changing the permissions on a binary:
9457 they can do this by using <prgn>dpkg-statoverride</prgn>, as
9458 described below.<footnote>
9459 Ordinary files installed by <prgn>dpkg</prgn> (as
9460 opposed to <tt>conffile</tt>s and other similar objects)
9461 normally have their permissions reset to the distributed
9462 permissions when the package is reinstalled. However,
9463 the use of <prgn>dpkg-statoverride</prgn> overrides this
9464 default behavior.
9465 </footnote>
9466 Another method you should consider is to create a group for
9467 people allowed to use the program(s) and make any setuid
9468 executables executable only by that group.
9469 </p>
9472 If you need to create a new user or group for your package
9473 there are two possibilities. Firstly, you may need to
9474 make some files in the binary package be owned by this
9475 user or group, or you may need to compile the user or
9476 group id (rather than just the name) into the binary
9477 (though this latter should be avoided if possible, as in
9478 this case you need a statically allocated id).</p>
9481 If you need a statically allocated id, you must ask for a
9482 user or group id from the <tt>base-passwd</tt> maintainer,
9483 and must not release the package until you have been
9484 allocated one. Once you have been allocated one you must
9485 either make the package depend on a version of the
9486 <tt>base-passwd</tt> package with the id present in
9487 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
9488 your package to create the user or group itself with the
9489 correct id (using <tt>adduser</tt>) in its
9490 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
9491 the <prgn>postinst</prgn> is to be preferred if it is
9492 possible, otherwise a pre-dependency will be needed on the
9493 <tt>adduser</tt> package.)
9494 </p>
9497 On the other hand, the program might be able to determine
9498 the uid or gid from the user or group name at runtime, so
9499 that a dynamically allocated id can be used. In this case
9500 you should choose an appropriate user or group name,
9501 discussing this on <prgn>debian-devel</prgn> and checking
9502 with the <package/base-passwd/ maintainer that it is unique and that
9503 they do not wish you to use a statically allocated id
9504 instead. When this has been checked you must arrange for
9505 your package to create the user or group if necessary using
9506 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
9507 <prgn>postinst</prgn> script (again, the latter is to be
9508 preferred if it is possible).
9509 </p>
9512 Note that changing the numeric value of an id associated
9513 with a name is very difficult, and involves searching the
9514 file system for all appropriate files. You need to think
9515 carefully whether a static or dynamic id is required, since
9516 changing your mind later will cause problems.
9517 </p>
9519 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
9521 This section is not intended as policy, but as a
9522 description of the use of <prgn>dpkg-statoverride</prgn>.
9523 </p>
9526 If a system administrator wishes to have a file (or
9527 directory or other such thing) installed with owner and
9528 permissions different from those in the distributed Debian
9529 package, they can use the <prgn>dpkg-statoverride</prgn>
9530 program to instruct <prgn>dpkg</prgn> to use the different
9531 settings every time the file is installed. Thus the
9532 package maintainer should distribute the files with their
9533 normal permissions, and leave it for the system
9534 administrator to make any desired changes. For example, a
9535 daemon which is normally required to be setuid root, but
9536 in certain situations could be used without being setuid,
9537 should be installed setuid in the <tt>.deb</tt>. Then the
9538 local system administrator can change this if they wish.
9539 If there are two standard ways of doing it, the package
9540 maintainer can use <tt>debconf</tt> to find out the
9541 preference, and call <prgn>dpkg-statoverride</prgn> in the
9542 maintainer script if necessary to accommodate the system
9543 administrator's choice. Care must be taken during
9544 upgrades to not override an existing setting.
9545 </p>
9548 Given the above, <prgn>dpkg-statoverride</prgn> is
9549 essentially a tool for system administrators and would not
9550 normally be needed in the maintainer scripts. There is
9551 one type of situation, though, where calls to
9552 <prgn>dpkg-statoverride</prgn> would be needed in the
9553 maintainer scripts, and that involves packages which use
9554 dynamically allocated user or group ids. In such a
9555 situation, something like the following idiom can be very
9556 helpful in the package's <prgn>postinst</prgn>, where
9557 <tt>sysuser</tt> is a dynamically allocated id:
9558 <example>
9559 for i in /usr/bin/foo /usr/sbin/bar
9561 # only do something when no setting exists
9562 if ! dpkg-statoverride --list $i >/dev/null 2>&1
9563 then
9564 #include: debconf processing, question about foo and bar
9565 if [ "$RET" = "true" ] ; then
9566 dpkg-statoverride --update --add sysuser root 4755 $i
9569 done
9570 </example>
9571 The corresponding code to remove the override when the package
9572 is purged would be:
9573 <example>
9574 for i in /usr/bin/foo /usr/sbin/bar
9576 if dpkg-statoverride --list $i >/dev/null 2>&1
9577 then
9578 dpkg-statoverride --remove $i
9580 done
9581 </example>
9582 </p>
9583 </sect1>
9584 </sect>
9586 <sect id="filenames">
9587 <heading>File names</heading>
9590 The name of the files installed by binary packages in the system PATH
9591 (namely <tt>/bin</tt>, <tt>/sbin</tt>, <tt>/usr/bin</tt>,
9592 <tt>/usr/sbin</tt> and <tt>/usr/games</tt>) must be encoded in
9593 ASCII.
9594 </p>
9597 The name of the files and directories installed by binary packages
9598 outside the system PATH must be encoded in UTF-8 and should be
9599 restricted to ASCII when it is possible to do so.
9600 </p>
9601 </sect>
9602 </chapt>
9605 <chapt id="customized-programs">
9606 <heading>Customized programs</heading>
9608 <sect id="arch-spec">
9609 <heading>Architecture specification strings</heading>
9612 If a program needs to specify an <em>architecture specification
9613 string</em> in some place, it should select one of the strings
9614 provided by <tt>dpkg-architecture -L</tt>. The strings are in
9615 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
9616 part is sometimes elided, as when the OS is Linux.
9617 </p>
9620 Note that we don't want to use
9621 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
9622 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
9623 since this would make our programs incompatible with other
9624 Linux distributions. We also don't use something like
9625 <tt><var>arch</var>-unknown-linux</tt>, since the
9626 <tt>unknown</tt> does not look very good.
9627 </p>
9629 <sect1 id="arch-wildcard-spec">
9630 <heading>Architecture wildcards</heading>
9633 A package may specify an architecture wildcard. Architecture
9634 wildcards are in the format <tt>any</tt> (which matches every
9635 architecture), <tt><var>os</var></tt>-any, or
9636 any-<tt><var>cpu</var></tt>. <footnote>
9637 Internally, the package system normalizes the GNU triplets
9638 and the Debian arches into Debian arch triplets (which are
9639 kind of inverted GNU triplets), with the first component of
9640 the triplet representing the libc and ABI in use, and then
9641 does matching against those triplets. However, such
9642 triplets are an internal implementation detail that should
9643 not be used by packages directly. The libc and ABI portion
9644 is handled internally by the package system based on
9645 the <var>os</var> and <var>cpu</var>.
9646 </footnote>
9647 </p>
9648 </sect1>
9649 </sect>
9651 <sect>
9652 <heading>Daemons</heading>
9655 The configuration files <file>/etc/services</file>,
9656 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
9657 by the <prgn>netbase</prgn> package and must not be modified
9658 by other packages.
9659 </p>
9662 If a package requires a new entry in one of these files, the
9663 maintainer should get in contact with the
9664 <prgn>netbase</prgn> maintainer, who will add the entries
9665 and release a new version of the <prgn>netbase</prgn>
9666 package.
9667 </p>
9670 The configuration file <file>/etc/inetd.conf</file> must not be
9671 modified by the package's scripts except via the
9672 <prgn>update-inetd</prgn> script or the
9673 <file>DebianNet.pm</file> Perl module. See their documentation
9674 for details on how to add entries.
9675 </p>
9678 If a package wants to install an example entry into
9679 <file>/etc/inetd.conf</file>, the entry must be preceded with
9680 exactly one hash character (<tt>#</tt>). Such lines are
9681 treated as "commented out by user" by the
9682 <prgn>update-inetd</prgn> script and are not changed or
9683 activated during package updates.
9684 </p>
9685 </sect>
9687 <sect>
9688 <heading>Using pseudo-ttys and modifying wtmp, utmp and
9689 lastlog</heading>
9692 Some programs need to create pseudo-ttys. This should be done
9693 using Unix98 ptys if the C library supports it. The resulting
9694 program must not be installed setuid root, unless that
9695 is required for other functionality.
9696 </p>
9699 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
9700 <file>/var/log/lastlog</file> must be installed writable by
9701 group <tt>utmp</tt>. Programs which need to modify those
9702 files must be installed setgid <tt>utmp</tt>.
9703 </p>
9704 </sect>
9706 <sect>
9707 <heading>Editors and pagers</heading>
9710 Some programs have the ability to launch an editor or pager
9711 program to edit or display a text document. Since there are
9712 lots of different editors and pagers available in the Debian
9713 distribution, the system administrator and each user should
9714 have the possibility to choose their preferred editor and
9715 pager.
9716 </p>
9719 In addition, every program should choose a good default
9720 editor/pager if none is selected by the user or system
9721 administrator.
9722 </p>
9725 Thus, every program that launches an editor or pager must
9726 use the EDITOR or PAGER environment variable to determine
9727 the editor or pager the user wishes to use. If these
9728 variables are not set, the programs <file>/usr/bin/editor</file>
9729 and <file>/usr/bin/pager</file> should be used, respectively.
9730 </p>
9733 These two files are managed through the <prgn>dpkg</prgn>
9734 "alternatives" mechanism. Every package providing an editor or
9735 pager must call the <prgn>update-alternatives</prgn> script to
9736 register as an alternative for <file>/usr/bin/editor</file>
9737 or <file>/usr/bin/pager</file> as appropriate. The alternative
9738 should have a slave alternative
9739 for <file>/usr/share/man/man1/editor.1.gz</file>
9740 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
9741 corresponding manual page.
9742 </p>
9745 If it is very hard to adapt a program to make use of the
9746 EDITOR or PAGER variables, that program may be configured to
9747 use <file>/usr/bin/sensible-editor</file> and
9748 <file>/usr/bin/sensible-pager</file> as the editor or pager
9749 program respectively. These are two scripts provided in the
9750 <package>sensible-utils</package> package that check the EDITOR
9751 and PAGER variables and launch the appropriate program, and fall
9752 back to <file>/usr/bin/editor</file>
9753 and <file>/usr/bin/pager</file> if the variable is not set.
9754 </p>
9757 A program may also use the VISUAL environment variable to
9758 determine the user's choice of editor. If it exists, it
9759 should take precedence over EDITOR. This is in fact what
9760 <file>/usr/bin/sensible-editor</file> does.
9761 </p>
9764 It is not required for a package to depend on
9765 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
9766 package to provide such virtual packages.<footnote>
9767 The Debian base system already provides an editor and a
9768 pager program.
9769 </footnote>
9770 </p>
9771 </sect>
9773 <sect id="web-appl">
9774 <heading>Web servers and applications</heading>
9777 This section describes the locations and URLs that should
9778 be used by all web servers and web applications in the
9779 Debian system.
9780 </p>
9783 <enumlist>
9784 <item>
9785 Cgi-bin executable files are installed in the
9786 directory
9787 <example compact="compact">
9788 /usr/lib/cgi-bin
9789 </example>
9790 or a subdirectory of that directory, and the script
9791 <example compact="compact">
9792 /usr/lib/cgi-bin/.../<var>cgi-bin-name</var>
9793 </example>
9794 should be referred to as
9795 <example compact="compact">
9796 http://localhost/cgi-bin/.../<var>cgi-bin-name</var>
9797 </example>
9798 </item>
9800 <item>
9801 <p>(Deleted)</p>
9802 </item>
9804 <item>
9805 <p>Access to images</p>
9807 It is recommended that images for a package be stored
9808 in <tt>/usr/share/images/<var>package</var></tt> and
9809 may be referred to through an alias <tt>/images/</tt>
9811 <example>
9812 http://localhost/images/&lt;package&gt;/&lt;filename&gt;
9813 </example>
9815 </p>
9816 </item>
9818 <item>
9819 <p>Web Document Root</p>
9822 Web Applications should try to avoid storing files in
9823 the Web Document Root. Instead they should use the
9824 /usr/share/doc/<var>package</var> directory for
9825 documents and register the Web Application via the
9826 <package>doc-base</package> package. If access to the
9827 web document root is unavoidable then use
9828 <example compact="compact">
9829 /var/www/html
9830 </example>
9831 as the Document Root. This might be just a symbolic
9832 link to the location where the system administrator
9833 has put the real document root.
9834 </p>
9835 </item>
9836 <item><p>Providing httpd and/or httpd-cgi</p>
9838 All web servers should provide the virtual package
9839 <tt>httpd</tt>. If a web server has CGI support it should
9840 provide <tt>httpd-cgi</tt> additionally.
9841 </p>
9843 All web applications which do not contain CGI scripts should
9844 depend on <tt>httpd</tt>, all those web applications which
9845 <tt>do</tt> contain CGI scripts, should depend on
9846 <tt>httpd-cgi</tt>.
9847 </p>
9848 </item>
9849 </enumlist>
9850 </p>
9851 </sect>
9853 <sect id="mail-transport-agents">
9854 <heading>Mail transport, delivery and user agents</heading>
9857 Debian packages which process electronic mail, whether mail
9858 user agents (MUAs) or mail transport agents (MTAs), must
9859 ensure that they are compatible with the configuration
9860 decisions below. Failure to do this may result in lost
9861 mail, broken <tt>From:</tt> lines, and other serious brain
9862 damage!
9863 </p>
9866 The mail spool is <file>/var/mail</file> and the interface to
9867 send a mail message is <file>/usr/sbin/sendmail</file> (as per
9868 the FHS). On older systems, the mail spool may be
9869 physically located in <file>/var/spool/mail</file>, but all
9870 access to the mail spool should be via the
9871 <file>/var/mail</file> symlink. The mail spool is part of the
9872 base system and not part of the MTA package.
9873 </p>
9876 All Debian MUAs, MTAs, MDAs and other mailbox accessing
9877 programs (such as IMAP daemons) must lock the mailbox in an
9878 NFS-safe way. This means that <tt>fcntl()</tt> locking must
9879 be combined with dot locking. To avoid deadlocks, a program
9880 should use <tt>fcntl()</tt> first and dot locking after
9881 this, or alternatively implement the two locking methods in
9882 a non blocking way<footnote>
9883 If it is not possible to establish both locks, the
9884 system shouldn't wait for the second lock to be
9885 established, but remove the first lock, wait a (random)
9886 time, and start over locking again.
9887 </footnote>. Using the functions <tt>maillock</tt> and
9888 <tt>mailunlock</tt> provided by the
9889 <tt>liblockfile*</tt><footnote>
9890 You will need to depend on <tt>liblockfile1 (&gt;&gt;1.01)</tt>
9891 to use these functions.
9892 </footnote> packages is the recommended way to realize this.
9893 </p>
9896 Mailboxes are generally either mode 600 and owned by
9897 <var>user</var> or mode 660 and owned by
9898 <tt><var>user</var>:mail</tt><footnote>
9899 There are two traditional permission schemes for mail spools:
9900 mode 600 with all mail delivery done by processes running as
9901 the destination user, or mode 660 and owned by group mail with
9902 mail delivery done by a process running as a system user in
9903 group mail. Historically, Debian required mode 660 mail
9904 spools to enable the latter model, but that model has become
9905 increasingly uncommon and the principle of least privilege
9906 indicates that mail systems that use the first model should
9907 use permissions of 600. If delivery to programs is permitted,
9908 it's easier to keep the mail system secure if the delivery
9909 agent runs as the destination user. Debian Policy therefore
9910 permits either scheme.
9911 </footnote>. The local system administrator may choose a
9912 different permission scheme; packages should not make
9913 assumptions about the permission and ownership of mailboxes
9914 unless required (such as when creating a new mailbox). A MUA
9915 may remove a mailbox (unless it has nonstandard permissions) in
9916 which case the MTA or another MUA must recreate it if needed.
9917 </p>
9920 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
9921 be setgid mail to do the locking mentioned above (and
9922 must obviously avoid accessing other users' mailboxes
9923 using this privilege).</p>
9926 <file>/etc/aliases</file> is the source file for the system mail
9927 aliases (e.g., postmaster, usenet, etc.), it is the one
9928 which the sysadmin and <prgn>postinst</prgn> scripts may
9929 edit. After <file>/etc/aliases</file> is edited the program or
9930 human editing it must call <prgn>newaliases</prgn>. All MTA
9931 packages must come with a <prgn>newaliases</prgn> program,
9932 even if it does nothing, but older MTA packages did not do
9933 this so programs should not fail if <prgn>newaliases</prgn>
9934 cannot be found. Note that because of this, all MTA
9935 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
9936 <tt>Replaces: mail-transport-agent</tt> control fields.
9937 </p>
9940 The convention of writing <tt>forward to
9941 <var>address</var></tt> in the mailbox itself is not
9942 supported. Use a <tt>.forward</tt> file instead.</p>
9945 The <prgn>rmail</prgn> program used by UUCP
9946 for incoming mail should be <file>/usr/sbin/rmail</file>.
9947 Likewise, <prgn>rsmtp</prgn>, for receiving
9948 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
9949 is supported.</p>
9952 If your package needs to know what hostname to use on (for
9953 example) outgoing news and mail messages which are generated
9954 locally, you should use the file <file>/etc/mailname</file>. It
9955 will contain the portion after the username and <tt>@</tt>
9956 (at) sign for email addresses of users on the machine
9957 (followed by a newline).
9958 </p>
9961 Such a package should check for the existence of this file
9962 when it is being configured. If it exists, it should be
9963 used without comment, although an MTA's configuration script
9964 may wish to prompt the user even if it finds that this file
9965 exists. If the file does not exist, the package should
9966 prompt the user for the value (preferably using
9967 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
9968 as well as using it in the package's configuration. The
9969 prompt should make it clear that the name will not just be
9970 used by that package. For example, in this situation the
9971 <tt>inn</tt> package could say something like:
9972 <example compact="compact">
9973 Please enter the "mail name" of your system. This is the
9974 hostname portion of the address to be shown on outgoing
9975 news and mail messages. The default is
9976 <var>syshostname</var>, your system's host name. Mail
9977 name ["<var>syshostname</var>"]:
9978 </example>
9979 where <var>syshostname</var> is the output of <tt>hostname
9980 --fqdn</tt>.
9981 </p>
9982 </sect>
9984 <sect>
9985 <heading>News system configuration</heading>
9988 All the configuration files related to the NNTP (news)
9989 servers and clients should be located under
9990 <file>/etc/news</file>.</p>
9993 There are some configuration issues that apply to a number
9994 of news clients and server packages on the machine. These
9995 are:
9997 <taglist>
9998 <tag><file>/etc/news/organization</file></tag>
9999 <item>
10000 A string which should appear as the
10001 organization header for all messages posted
10002 by NNTP clients on the machine
10003 </item>
10005 <tag><file>/etc/news/server</file></tag>
10006 <item>
10007 Contains the FQDN of the upstream NNTP
10008 server, or localhost if the local machine is
10009 an NNTP server.
10010 </item>
10011 </taglist>
10013 Other global files may be added as required for cross-package news
10014 configuration.
10015 </p>
10016 </sect>
10019 <sect>
10020 <heading>Programs for the X Window System</heading>
10022 <sect1>
10023 <heading>Providing X support and package priorities</heading>
10026 Programs that can be configured with support for the X
10027 Window System must be configured to do so and must declare
10028 any package dependencies necessary to satisfy their
10029 runtime requirements when using the X Window System. If
10030 such a package is of higher priority than the X packages
10031 on which it depends, it is required that either the
10032 X-specific components be split into a separate package, or
10033 that an alternative version of the package, which includes
10034 X support, be provided, or that the package's priority be
10035 lowered.
10036 </p>
10037 </sect1>
10039 <sect1>
10040 <heading>Packages providing an X server</heading>
10043 Packages that provide an X server that, directly or
10044 indirectly, communicates with real input and display
10045 hardware should declare in their <tt>Provides</tt> control
10046 field that they provide the virtual
10047 package <tt>xserver</tt>.<footnote>
10048 This implements current practice, and provides an
10049 actual policy for usage of the <tt>xserver</tt>
10050 virtual package which appears in the virtual packages
10051 list. In a nutshell, X servers that interface
10052 directly with the display and input hardware or via
10053 another subsystem (e.g., GGI) should provide
10054 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
10055 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
10056 </footnote>
10057 </p>
10058 </sect1>
10060 <sect1>
10061 <heading>Packages providing a terminal emulator</heading>
10064 Packages that provide a terminal emulator for the X Window
10065 System which meet the criteria listed below should declare in
10066 their <tt>Provides</tt> control field that they provide the
10067 virtual package <tt>x-terminal-emulator</tt>. They should
10068 also register themselves as an alternative for
10069 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
10070 20. That alternative should have a slave alternative
10071 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
10072 pointing to the corresponding manual page.
10073 </p>
10076 To be an <tt>x-terminal-emulator</tt>, a program must:
10077 <list compact="compact">
10078 <item>
10079 Be able to emulate a DEC VT100 terminal, or a
10080 compatible terminal.
10081 </item>
10083 <item>
10084 Support the command-line option <tt>-e
10085 <var>command</var></tt>, which creates a new
10086 terminal window<footnote>
10087 "New terminal window" does not necessarily mean
10088 a new top-level X window directly parented by
10089 the window manager; it could, if the terminal
10090 emulator application were so coded, be a new
10091 "view" in a multiple-document interface (MDI).
10092 </footnote>
10093 and runs the specified <var>command</var>,
10094 interpreting the entirety of the rest of the command
10095 line as a command to pass straight to exec, in the
10096 manner that <tt>xterm</tt> does.
10097 </item>
10099 <item>
10100 Support the command-line option <tt>-T
10101 <var>title</var></tt>, which creates a new terminal
10102 window with the window title <var>title</var>.
10103 </item>
10104 </list>
10105 </p>
10106 </sect1>
10108 <sect1>
10109 <heading>Packages providing a window manager</heading>
10112 Packages that provide a window manager should declare in
10113 their <tt>Provides</tt> control field that they provide the
10114 virtual package <tt>x-window-manager</tt>. They should also
10115 register themselves as an alternative for
10116 <file>/usr/bin/x-window-manager</file>, with a priority
10117 calculated as follows:
10118 <list compact="compact">
10119 <item>
10120 Start with a priority of 20.
10121 </item>
10123 <item>
10124 If the window manager supports the Debian menu
10125 system, add 20 points if this support is available
10126 in the package's default configuration (i.e., no
10127 configuration files belonging to the system or user
10128 have to be edited to activate the feature); if
10129 configuration files must be modified, add only 10
10130 points.
10131 </p>
10132 </item>
10134 <item>
10135 If the window manager complies with <url
10136 id="http://www.freedesktop.org/wiki/Specifications/wm-spec"
10137 name="The Window Manager Specification Project">,
10138 written by the <url id="http://www.freedesktop.org/wiki/"
10139 name="Free Desktop Group">, add 40 points.
10140 </item>
10142 <item>
10143 If the window manager permits the X session to be
10144 restarted using a <em>different</em> window manager
10145 (without killing the X server) in its default
10146 configuration, add 10 points; otherwise add none.
10147 </item>
10148 </list>
10149 That alternative should have a slave alternative
10150 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
10151 pointing to the corresponding manual page.
10152 </p>
10153 </sect1>
10155 <sect1>
10156 <heading>Packages providing fonts</heading>
10159 Packages that provide fonts for the X Window
10160 System<footnote>
10161 For the purposes of Debian Policy, a "font for the X
10162 Window System" is one which is accessed via X protocol
10163 requests. Fonts for the Linux console, for PostScript
10164 renderer, or any other purpose, do not fit this
10165 definition. Any tool which makes such fonts available
10166 to the X Window System, however, must abide by this
10167 font policy.
10168 </footnote>
10169 must do a number of things to ensure that they are both
10170 available without modification of the X or font server
10171 configuration, and that they do not corrupt files used by
10172 other font packages to register information about
10173 themselves.
10174 <enumlist>
10175 <item>
10176 Fonts of any type supported by the X Window System
10177 must be in a separate binary package from any
10178 executables, libraries, or documentation (except
10179 that specific to the fonts shipped, such as their
10180 license information). If one or more of the fonts
10181 so packaged are necessary for proper operation of
10182 the package with which they are associated the font
10183 package may be Recommended; if the fonts merely
10184 provide an enhancement, a Suggests relationship may
10185 be used. Packages must not Depend on font
10186 packages.<footnote>
10187 This is because the X server may retrieve fonts
10188 from the local file system or over the network
10189 from an X font server; the Debian package system
10190 is empowered to deal only with the local
10191 file system.
10192 </footnote>
10193 </item>
10195 <item>
10196 BDF fonts must be converted to PCF fonts with the
10197 <prgn>bdftopcf</prgn> utility (available in the
10198 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
10199 placed in a directory that corresponds to their
10200 resolution:
10201 <list compact="compact">
10202 <item>
10203 100 dpi fonts must be placed in
10204 <file>/usr/share/fonts/X11/100dpi/</file>.
10205 </item>
10207 <item>
10208 75 dpi fonts must be placed in
10209 <file>/usr/share/fonts/X11/75dpi/</file>.
10210 </item>
10212 <item>
10213 Character-cell fonts, cursor fonts, and other
10214 low-resolution fonts must be placed in
10215 <file>/usr/share/fonts/X11/misc/</file>.
10216 </item>
10217 </list>
10218 </item>
10220 <item>
10221 Type 1 fonts must be placed in
10222 <file>/usr/share/fonts/X11/Type1/</file>. If font
10223 metric files are available, they must be placed here
10224 as well.
10225 </item>
10227 <item>
10228 Subdirectories of <file>/usr/share/fonts/X11/</file>
10229 other than those listed above must be neither
10230 created nor used. (The <file>PEX</file>, <file>CID</file>,
10231 <file>Speedo</file>, and <file>cyrillic</file> directories
10232 are excepted for historical reasons, but installation of
10233 files into these directories remains discouraged.)
10234 </item>
10236 <item>
10237 Font packages may, instead of placing files directly
10238 in the X font directories listed above, provide
10239 symbolic links in that font directory pointing to
10240 the files' actual location in the filesystem. Such
10241 a location must comply with the FHS.
10242 </item>
10244 <item>
10245 Font packages should not contain both 75dpi and
10246 100dpi versions of a font. If both are available,
10247 they should be provided in separate binary packages
10248 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
10249 the names of the packages containing the
10250 corresponding fonts.
10251 </item>
10253 <item>
10254 Fonts destined for the <file>misc</file> subdirectory
10255 should not be included in the same package as 75dpi
10256 or 100dpi fonts; instead, they should be provided in
10257 a separate package with <tt>-misc</tt> appended to
10258 its name.
10259 </item>
10261 <item>
10262 Font packages must not provide the files
10263 <file>fonts.dir</file>, <file>fonts.alias</file>, or
10264 <file>fonts.scale</file> in a font directory:
10265 <list>
10266 <item>
10267 <file>fonts.dir</file> files must not be provided at all.
10268 </item>
10270 <item>
10271 <file>fonts.alias</file> and <file>fonts.scale</file>
10272 files, if needed, should be provided in the
10273 directory
10274 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
10275 where <var>fontdir</var> is the name of the
10276 subdirectory of
10277 <file>/usr/share/fonts/X11/</file> where the
10278 package's corresponding fonts are stored
10279 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
10280 <var>package</var> is the name of the package
10281 that provides these fonts, and
10282 <var>extension</var> is either <tt>scale</tt>
10283 or <tt>alias</tt>, whichever corresponds to
10284 the file contents.
10285 </item>
10286 </list>
10287 </item>
10289 <item>
10290 Font packages must declare a dependency on
10291 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
10292 or <tt>Pre-Depends</tt> control field.
10293 </item>
10295 <item>
10296 Font packages that provide one or more
10297 <file>fonts.scale</file> files as described above must
10298 invoke <prgn>update-fonts-scale</prgn> on each
10299 directory into which they installed fonts
10300 <em>before</em> invoking
10301 <prgn>update-fonts-dir</prgn> on that directory.
10302 This invocation must occur in both the
10303 <prgn>postinst</prgn> (for all arguments) and
10304 <prgn>postrm</prgn> (for all arguments except
10305 <tt>upgrade</tt>) scripts.
10306 </item>
10308 <item>
10309 Font packages that provide one or more
10310 <file>fonts.alias</file> files as described above must
10311 invoke <prgn>update-fonts-alias</prgn> on each
10312 directory into which they installed fonts. This
10313 invocation must occur in both the
10314 <prgn>postinst</prgn> (for all arguments) and
10315 <prgn>postrm</prgn> (for all arguments except
10316 <tt>upgrade</tt>) scripts.
10317 </item>
10319 <item>
10320 Font packages must invoke
10321 <prgn>update-fonts-dir</prgn> on each directory into
10322 which they installed fonts. This invocation must
10323 occur in both the <prgn>postinst</prgn> (for all
10324 arguments) and <prgn>postrm</prgn> (for all
10325 arguments except <tt>upgrade</tt>) scripts.
10326 </item>
10328 <item>
10329 Font packages must not provide alias names for the
10330 fonts they include which collide with alias names
10331 already in use by fonts already packaged.
10332 </item>
10334 <item>
10335 Font packages must not provide fonts with the same
10336 XLFD registry name as another font already packaged.
10337 </item>
10338 </enumlist>
10339 </p>
10340 </sect1>
10342 <sect1 id="appdefaults">
10343 <heading>Application defaults files</heading>
10346 Application defaults files must be installed in the
10347 directory <file>/etc/X11/app-defaults/</file> (use of a
10348 localized subdirectory of <file>/etc/X11/</file> as described
10349 in the <em>X Toolkit Intrinsics - C Language
10350 Interface</em> manual is also permitted). They must be
10351 registered as <tt>conffile</tt>s or handled as
10352 configuration files.
10353 </p>
10356 Customization of programs' X resources may also be
10357 supported with the provision of a file with the same name
10358 as that of the package placed in
10359 the <file>/etc/X11/Xresources/</file> directory, which
10360 must be registered as a <tt>conffile</tt> or handled as a
10361 configuration file.<footnote>
10362 Note that this mechanism is not the same as using
10363 app-defaults; app-defaults are tied to the client
10364 binary on the local file system, whereas X resources
10365 are stored in the X server and affect all connecting
10366 clients.
10367 </footnote>
10368 </p>
10369 </sect1>
10371 <sect1>
10372 <heading>Installation directory issues</heading>
10375 Historically, packages using the X Window System used a
10376 separate set of installation directories from other packages.
10377 This practice has been discontinued and packages using the X
10378 Window System should now generally be installed in the same
10379 directories as any other package. Specifically, packages must
10380 not install files under the <file>/usr/X11R6/</file> directory
10381 and the <file>/usr/X11R6/</file> directory hierarchy should be
10382 regarded as obsolete.
10383 </p>
10386 Include files previously installed under
10387 <file>/usr/X11R6/include/X11/</file> should be installed into
10388 <file>/usr/include/X11/</file>. For files previously
10389 installed into subdirectories of
10390 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
10391 determine if subdirectories of <file>/usr/lib/</file> and
10392 <file>/usr/share/</file> can be used. If not, a subdirectory
10393 of <file>/usr/lib/X11/</file> should be used.
10394 </p>
10397 Configuration files for window, display, or session managers
10398 or other applications that are tightly integrated with the X
10399 Window System may be placed in a subdirectory
10400 of <file>/etc/X11/</file> corresponding to the package name.
10401 Other X Window System applications should use
10402 the <file>/etc/</file> directory unless otherwise mandated by
10403 policy (such as for <ref id="appdefaults">).
10404 </p>
10405 </sect1>
10406 </sect>
10408 <sect id="perl">
10409 <heading>Perl programs and modules</heading>
10412 Perl programs and modules should follow the current Perl policy.
10413 </p>
10416 The Perl policy can be found in the <tt>perl-policy</tt>
10417 files in the <tt>debian-policy</tt> package.
10418 It is also available from the Debian web mirrors at
10419 <tt><url name="/doc/packaging-manuals/perl-policy/"
10420 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
10421 </p>
10422 </sect>
10424 <sect id="emacs">
10425 <heading>Emacs lisp programs</heading>
10428 Please refer to the "Debian Emacs Policy" for details of how to
10429 package emacs lisp programs.
10430 </p>
10433 The Emacs policy is available in
10434 <file>debian-emacs-policy.gz</file> of the
10435 <package>emacsen-common</package> package.
10436 It is also available from the Debian web mirrors at
10437 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
10438 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
10439 </p>
10440 </sect>
10442 <sect>
10443 <heading>Games</heading>
10446 The permissions on <file>/var/games</file> are mode 755, owner
10447 <tt>root</tt> and group <tt>root</tt>.
10448 </p>
10451 Each game decides on its own security policy.</p>
10454 Games which require protected, privileged access to
10455 high-score files, saved games, etc., may be made
10456 set-<em>group</em>-id (mode 2755) and owned by
10457 <tt>root:games</tt>, and use files and directories with
10458 appropriate permissions (770 <tt>root:games</tt>, for
10459 example). They must not be made
10460 set-<em>user</em>-id, as this causes security problems. (If
10461 an attacker can subvert any set-user-id game they can
10462 overwrite the executable of any other, causing other players
10463 of these games to run a Trojan horse program. With a
10464 set-group-id game the attacker only gets access to less
10465 important game data, and if they can get at the other
10466 players' accounts at all it will take considerably more
10467 effort.)</p>
10470 Some packages, for example some fortune cookie programs, are
10471 configured by the upstream authors to install with their
10472 data files or other static information made unreadable so
10473 that they can only be accessed through set-id programs
10474 provided. You should not do this in a Debian package: anyone can
10475 download the <file>.deb</file> file and read the data from it,
10476 so there is no point making the files unreadable. Not
10477 making the files unreadable also means that you don't have
10478 to make so many programs set-id, which reduces the risk of a
10479 security hole.</p>
10482 As described in the FHS, binaries of games should be
10483 installed in the directory <file>/usr/games</file>. This also
10484 applies to games that use the X Window System. Manual pages
10485 for games (X and non-X games) should be installed in
10486 <file>/usr/share/man/man6</file>.</p>
10487 </sect>
10488 </chapt>
10491 <chapt id="docs">
10492 <heading>Documentation</heading>
10494 <sect>
10495 <heading>Manual pages</heading>
10498 You should install manual pages in <prgn>nroff</prgn> source
10499 form, in appropriate places under <file>/usr/share/man</file>.
10500 You should only use sections 1 to 9 (see the FHS for more
10501 details). You must not install a pre-formatted "cat page".
10502 </p>
10505 Each program, utility, and function should have an
10506 associated manual page included in the same package. It is
10507 suggested that all configuration files also have a manual
10508 page included as well. Manual pages for protocols and other
10509 auxiliary things are optional.
10510 </p>
10513 If no manual page is available, this is considered as a bug
10514 and should be reported to the Debian Bug Tracking System (the
10515 maintainer of the package is allowed to write this bug report
10516 themselves, if they so desire). Do not close the bug report
10517 until a proper man page is available.<footnote>
10518 It is not very hard to write a man page. See the
10519 <url id="http://www.schweikhardt.net/man_page_howto.html"
10520 name="Man-Page-HOWTO">,
10521 <manref name="man" section="7">, the examples created
10522 by <prgn>dh_make</prgn>, the helper
10523 program <prgn>help2man</prgn>, or the
10524 directory <file>/usr/share/doc/man-db/examples</file>.
10525 </footnote>
10526 </p>
10529 You may forward a complaint about a missing man page to the
10530 upstream authors, and mark the bug as forwarded in the
10531 Debian bug tracking system. Even though the GNU Project do
10532 not in general consider the lack of a man page to be a bug,
10533 we do; if they tell you that they don't consider it a bug
10534 you should leave the bug in our bug tracking system open
10535 anyway.
10536 </p>
10539 Manual pages should be installed compressed using <tt>gzip -9</tt>.
10540 </p>
10543 If one man page needs to be accessible via several names it
10544 is better to use a symbolic link than the <file>.so</file>
10545 feature, but there is no need to fiddle with the relevant
10546 parts of the upstream source to change from <file>.so</file> to
10547 symlinks: don't do it unless it's easy. You should not
10548 create hard links in the manual page directories, nor put
10549 absolute filenames in <file>.so</file> directives. The filename
10550 in a <file>.so</file> in a man page should be relative to the
10551 base of the man page tree (usually
10552 <file>/usr/share/man</file>). If you do not create any links
10553 (whether symlinks, hard links, or <tt>.so</tt> directives)
10554 in the file system to the alternate names of the man page,
10555 then you should not rely on <prgn>man</prgn> finding your
10556 man page under those names based solely on the information in
10557 the man page's header.<footnote>
10558 Supporting this in <prgn>man</prgn> often requires
10559 unreasonable processing time to find a manual page or to
10560 report that none exists, and moves knowledge into man's
10561 database that would be better left in the file system.
10562 This support is therefore deprecated and will cease to
10563 be present in the future.
10564 </footnote>
10565 </p>
10568 Manual pages in locale-specific subdirectories of
10569 <file>/usr/share/man</file> should use either UTF-8 or the usual
10570 legacy encoding for that language (normally the one corresponding
10571 to the shortest relevant locale name in
10572 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
10573 <file>/usr/share/man/fr</file> should use either UTF-8 or
10574 ISO-8859-1.<footnote>
10575 <prgn>man</prgn> will automatically detect whether UTF-8 is in
10576 use. In future, all manual pages will be required to use
10577 UTF-8.
10578 </footnote>
10579 </p>
10582 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
10583 included in the subdirectory name unless it indicates a
10584 significant difference in the language, as this excludes
10585 speakers of the language in other countries.<footnote>
10586 At the time of writing, Chinese and Portuguese are the main
10587 languages with such differences, so <file>pt_BR</file>,
10588 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
10589 </footnote>
10590 </p>
10593 If a localized version of a manual page is provided, it should
10594 either be up-to-date or it should be obvious to the reader that
10595 it is outdated and the original manual page should be used
10596 instead. This can be done either by a note at the beginning of
10597 the manual page or by showing the missing or changed portions in
10598 the original language instead of the target language.
10599 </p>
10600 </sect>
10602 <sect>
10603 <heading>Info documents</heading>
10606 Info documents should be installed in <file>/usr/share/info</file>.
10607 They should be compressed with <tt>gzip -9</tt>.
10608 </p>
10611 The <prgn>install-info</prgn> program maintains a directory of
10612 installed info documents in <file>/usr/share/info/dir</file> for the
10613 use of info readers. This file must not be included in packages
10614 other than <package>install-info</package>.
10615 </p>
10618 <prgn>install-info</prgn> is automatically invoked when
10619 appropriate using dpkg triggers. Packages other than
10620 <package>install-info</package> <em>should not</em> invoke
10621 <prgn>install-info</prgn> directly and <em>should not</em>
10622 depend on, recommend, or suggest <package>install-info</package>
10623 for this purpose.
10624 </p>
10627 Info readers requiring the <file>/usr/share/info/dir</file> file
10628 should depend on <package>install-info</package>.
10629 </p>
10632 Info documents should contain section and directory entry
10633 information in the document for the use
10634 of <prgn>install-info</prgn>. The section should be specified
10635 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
10636 space and the section of this info page. The directory entry or
10637 entries should be included between
10638 a <tt>START-INFO-DIR-ENTRY</tt> line and
10639 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
10640 <example>
10641 INFO-DIR-SECTION Individual utilities
10642 START-INFO-DIR-ENTRY
10643 * example: (example). An example info directory entry.
10644 END-INFO-DIR-ENTRY
10645 </example>
10646 To determine which section to use, you should look
10647 at <file>/usr/share/info/dir</file> on your system and choose
10648 the most relevant (or create a new section if none of the
10649 current sections are relevant).<footnote>
10650 Normally, info documents are generated from Texinfo source.
10651 To include this information in the generated info document, if
10652 it is absent, add commands like:
10653 <example>
10654 @dircategory Individual utilities
10655 @direntry
10656 * example: (example). An example info directory entry.
10657 @end direntry
10658 </example>
10659 to the Texinfo source of the document and ensure that the info
10660 documents are rebuilt from source during the package build.
10661 </footnote>
10662 </p>
10663 </sect>
10665 <sect id="docs-additional">
10666 <heading>Additional documentation</heading>
10669 Any additional documentation that comes with the package may be
10670 installed at the discretion of the package maintainer. It is
10671 often a good idea to include text information files
10672 (<file>README</file>s, FAQs, and so forth) that come with the
10673 source package in the binary package. However, you don't need
10674 to install the instructions for building and installing the
10675 package, of course!
10676 </p>
10679 Plain text documentation should be compressed with <tt>gzip
10680 -9</tt> unless it is small.
10681 </p>
10684 If a package comes with large amounts of documentation that many
10685 users of the package will not require, you should create a
10686 separate binary package to contain it so that it does not take
10687 up disk space on the machines of users who do not need or want
10688 it installed. As a special case of this rule, shared library
10689 documentation of any appreciable size should always be packaged
10690 with the library development package (<ref id="sharedlibs-dev">)
10691 or in a separate documentation package, since shared libraries
10692 are frequently installed as dependencies of other packages by
10693 users who have little interest in documentation of the library
10694 itself. The documentation package for the
10695 package <var>package</var> is conventionally
10696 named <var>package</var>-doc
10697 (or <var>package</var>-doc-<var>language-code</var> if there are
10698 separate documentation packages for multiple languages).
10699 </p>
10702 Additional documentation included in the package should be
10703 installed under <file>/usr/share/doc/<var>package</var></file>.
10704 If the documentation is packaged separately,
10705 as <var>package</var>-doc for example, it may be installed under
10706 either that path or into the documentation directory for the
10707 separate documentation package
10708 (<file>/usr/share/doc/<var>package</var>-doc</file> in this
10709 example). However, installing the documentation into the
10710 documentation directory of the main package is preferred since
10711 it is independent of the packaging method and will be easier for
10712 users to find.
10713 </p>
10716 Any separate package providing documentation must still install
10717 standard documentation files in its
10718 own <file>/usr/share/doc</file> directory as specified in the
10719 rest of this policy. See, for example, <ref id="copyrightfile">
10720 and <ref id="changelogs">.
10721 </p>
10724 Packages must not require the existence of any files in
10725 <file>/usr/share/doc/</file> in order to function
10726 <footnote>
10727 The system administrator should be able to delete files
10728 in <file>/usr/share/doc/</file> without causing any programs
10729 to break.
10730 </footnote>. Any files that are used or read by programs but
10731 are also useful as stand alone documentation should be installed
10732 elsewhere, such as
10733 under <file>/usr/share/<var>package</var>/</file>, and then
10734 included via symbolic links
10735 in <file>/usr/share/doc/<var>package</var></file>.
10736 </p>
10739 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
10740 link to another directory in <file>/usr/share/doc</file> only if
10741 the two packages both come from the same source and the
10742 first package Depends on the second.<footnote>
10744 Please note that this does not override the section on
10745 changelog files below, so the file
10746 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
10747 must refer to the changelog for the current version of
10748 <var>package</var> in question. In practice, this means
10749 that the sources of the target and the destination of the
10750 symlink must be the same (same source package and
10751 version).
10752 </p>
10753 </footnote>
10754 </p>
10755 </sect>
10757 <sect>
10758 <heading>Preferred documentation formats</heading>
10761 The unification of Debian documentation is being carried out
10762 via HTML.</p>
10765 If the package comes with extensive documentation in a
10766 markup format that can be converted to various other formats
10767 you should if possible ship HTML versions in a binary
10768 package.<footnote>
10769 Rationale: The important thing here is that HTML
10770 documentation should be available from <em>some</em>
10771 binary package.
10772 </footnote>
10773 The documentation must be installed as specified in
10774 <ref id="docs-additional">.
10775 </p>
10778 Other formats such as PostScript may be provided at the
10779 package maintainer's discretion.
10780 </p>
10781 </sect>
10783 <sect id="copyrightfile">
10784 <heading>Copyright information</heading>
10787 Every package must be accompanied by a verbatim copy of its
10788 copyright information and distribution license in the file
10789 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
10790 file must neither be compressed nor be a symbolic link.
10791 </p>
10794 In addition, the copyright file must say where the upstream
10795 sources (if any) were obtained, and should name the original
10796 authors.
10797 </p>
10800 Packages in the <em>contrib</em> or <em>non-free</em> archive
10801 areas should state in the copyright file that the package is not
10802 part of the Debian distribution and briefly explain why.
10803 </p>
10806 A copy of the file which will be installed in
10807 <file>/usr/share/doc/<var>package</var>/copyright</file> should
10808 be in <file>debian/copyright</file> in the source package.
10809 </p>
10812 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
10813 link to another directory in <file>/usr/share/doc</file> only if
10814 the two packages both come from the same source and the
10815 first package Depends on the second. These rules are important
10816 because <file>copyright</file> files must be extractable by
10817 mechanical means.
10818 </p>
10821 Packages distributed under the Apache license (version 2.0), the
10822 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
10823 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
10824 1.3) should refer to the corresponding files
10825 under <file>/usr/share/common-licenses</file>,<footnote>
10827 In particular,
10828 <file>/usr/share/common-licenses/Apache-2.0</file>,
10829 <file>/usr/share/common-licenses/Artistic</file>,
10830 <file>/usr/share/common-licenses/GPL-1</file>,
10831 <file>/usr/share/common-licenses/GPL-2</file>,
10832 <file>/usr/share/common-licenses/GPL-3</file>,
10833 <file>/usr/share/common-licenses/LGPL-2</file>,
10834 <file>/usr/share/common-licenses/LGPL-2.1</file>,
10835 <file>/usr/share/common-licenses/LGPL-3</file>,
10836 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
10837 <file>/usr/share/common-licenses/GFDL-1.3</file>
10838 respectively. The University of California BSD license is
10839 also included in <package>base-files</package> as
10840 <file>/usr/share/common-licenses/BSD</file>, but given the
10841 brevity of this license, its specificity to code whose
10842 copyright is held by the Regents of the University of
10843 California, and the frequency of minor wording changes, its
10844 text should be included in the copyright file rather than
10845 referencing this file.
10846 </p>
10847 </footnote> rather than quoting them in the copyright
10848 file.
10849 </p>
10852 You should not use the copyright file as a general <file>README</file>
10853 file. If your package has such a file it should be
10854 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
10855 <file>README.Debian</file> or some other appropriate place.
10856 </p>
10859 All copyright files must be encoded in UTF-8.
10860 </p>
10862 <sect1 id="copyrightformat">
10863 <heading>Machine-readable copyright information</heading>
10866 A specification for a standard, machine-readable format
10867 for <file>debian/copyright</file> files is maintained as part
10868 of the <package>debian-policy</package> package. This
10869 document may be found in the <file>copyright-format</file>
10870 files in the <package>debian-policy</package> package. It is
10871 also available from the Debian web mirrors at
10872 <tt><url name="/doc/packaging-manuals/copyright-format/1.0/"
10873 id="http://www.debian.org/doc/packaging-manuals/copyright-format/1.0/"></tt>.
10874 </p>
10877 Use of this format is optional.
10878 </p>
10879 </sect1>
10880 </sect>
10882 <sect>
10883 <heading>Examples</heading>
10886 Any examples (configurations, source files, whatever),
10887 should be installed in a directory
10888 <file>/usr/share/doc/<var>package</var>/examples</file>. These
10889 files should not be referenced by any program: they're there
10890 for the benefit of the system administrator and users as
10891 documentation only. Architecture-specific example files
10892 should be installed in a directory
10893 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
10894 links to them from
10895 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
10896 latter directory itself may be a symbolic link to the
10897 former.
10898 </p>
10901 If the purpose of a package is to provide examples, then the
10902 example files may be installed into
10903 <file>/usr/share/doc/<var>package</var></file>.
10904 </p>
10905 </sect>
10907 <sect id="changelogs">
10908 <heading>Changelog files</heading>
10911 Packages that are not Debian-native must contain a
10912 compressed copy of the <file>debian/changelog</file> file from
10913 the Debian source tree in
10914 <file>/usr/share/doc/<var>package</var></file> with the name
10915 <file>changelog.Debian.gz</file>.
10916 </p>
10919 If an upstream changelog is available, it should be accessible as
10920 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
10921 plain text. If the upstream changelog is distributed in
10922 HTML, it should be made available in that form as
10923 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
10924 and a plain text <file>changelog.gz</file> should be generated
10925 from it using, for example, <tt>lynx -dump -nolist</tt>. If
10926 the upstream changelog files do not already conform to this
10927 naming convention, then this may be achieved either by
10928 renaming the files, or by adding a symbolic link, at the
10929 maintainer's discretion.<footnote>
10930 Rationale: People should not have to look in places for
10931 upstream changelogs merely because they are given
10932 different names or are distributed in HTML format.
10933 </footnote>
10934 </p>
10937 All of these files should be installed compressed using
10938 <tt>gzip -9</tt>, as they will become large with time even
10939 if they start out small.
10940 </p>
10943 If the package has only one changelog which is used both as
10944 the Debian changelog and the upstream one because there is
10945 no separate upstream maintainer then that changelog should
10946 usually be installed as
10947 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
10948 there is a separate upstream maintainer, but no upstream
10949 changelog, then the Debian changelog should still be called
10950 <file>changelog.Debian.gz</file>.
10951 </p>
10954 For details about the format and contents of the Debian
10955 changelog file, please see <ref id="dpkgchangelog">.
10956 </p>
10957 </sect>
10958 </chapt>
10960 <appendix id="pkg-scope">
10961 <heading>Introduction and scope of these appendices</heading>
10964 These appendices are taken essentially verbatim from the
10965 now-deprecated Packaging Manual, version 3.2.1.0. They are
10966 the chapters which are likely to be of use to package
10967 maintainers and which have not already been included in the
10968 policy document itself. Most of these sections are very likely
10969 not relevant to policy; they should be treated as
10970 documentation for the packaging system. Please note that these
10971 appendices are included for convenience, and for historical
10972 reasons: they used to be part of policy package, and they have
10973 not yet been incorporated into dpkg documentation. However,
10974 they still have value, and hence they are presented here.
10975 </p>
10978 They have not yet been checked to ensure that they are
10979 compatible with the contents of policy, and if there are any
10980 contradictions, the version in the main policy document takes
10981 precedence. The remaining chapters of the old Packaging
10982 Manual have also not been read in detail to ensure that there
10983 are not parts which have been left out. Both of these will be
10984 done in due course.
10985 </p>
10988 Certain parts of the Packaging manual were integrated into the
10989 Policy Manual proper, and removed from the appendices. Links
10990 have been placed from the old locations to the new ones.
10991 </p>
10994 <prgn>dpkg</prgn> is a suite of programs for creating binary
10995 package files and installing and removing them on Unix
10996 systems.<footnote>
10997 <prgn>dpkg</prgn> is targeted primarily at Debian, but may
10998 work on or be ported to other systems.
10999 </footnote>
11000 </p>
11003 The binary packages are designed for the management of
11004 installed executable programs (usually compiled binaries) and
11005 their associated data, though source code examples and
11006 documentation are provided as part of some packages.</p>
11009 This manual describes the technical aspects of creating Debian
11010 binary packages (<file>.deb</file> files). It documents the
11011 behavior of the package management programs
11012 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
11013 they interact with packages.</p>
11016 This manual does not go into detail about the options and
11017 usage of the package building and installation tools. It
11018 should therefore be read in conjunction with those programs'
11019 man pages.
11020 </p>
11023 The utility programs which are provided with <prgn>dpkg</prgn>
11024 not described in detail here, are documented in their man pages.
11025 </p>
11028 It is assumed that the reader is reasonably familiar with the
11029 <prgn>dpkg</prgn> System Administrators' manual.
11030 Unfortunately this manual does not yet exist.
11031 </p>
11034 The Debian version of the FSF's GNU hello program is provided as
11035 an example for people wishing to create Debian packages. However,
11036 while the examples are helpful, they do not replace the need to
11037 read and follow the Policy and Programmer's Manual.</p>
11038 </appendix>
11040 <appendix id="pkg-binarypkg">
11041 <heading>Binary packages (from old Packaging Manual)</heading>
11044 See <manref name="deb" section="5"> and <ref id="pkg-controlarea">.
11045 </p>
11047 <sect id="pkg-bincreating"><heading>Creating package files -
11048 <prgn>dpkg-deb</prgn>
11049 </heading>
11052 All manipulation of binary package files is done by
11053 <prgn>dpkg-deb</prgn>; it's the only program that has
11054 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
11055 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
11056 will spot that the options requested are appropriate to
11057 <prgn>dpkg-deb</prgn> and invoke that instead with the same
11058 arguments.)
11059 </p>
11062 In order to create a binary package you must make a
11063 directory tree which contains all the files and directories
11064 you want to have in the file system data part of the package.
11065 In Debian-format source packages this directory is usually
11066 <file>debian/tmp</file>, relative to the top of the package's
11067 source tree.
11068 </p>
11071 They should have the locations (relative to the root of the
11072 directory tree you're constructing) ownerships and
11073 permissions which you want them to have on the system when
11074 they are installed.
11075 </p>
11078 With current versions of <prgn>dpkg</prgn> the uid/username
11079 and gid/groupname mappings for the users and groups being
11080 used should be the same on the system where the package is
11081 built and the one where it is installed.
11082 </p>
11085 You need to add one special directory to the root of the
11086 miniature file system tree you're creating:
11087 <prgn>DEBIAN</prgn>. It should contain the control
11088 information files, notably the binary package control file
11089 (see <ref id="pkg-controlfile">).
11090 </p>
11093 The <prgn>DEBIAN</prgn> directory will not appear in the
11094 file system archive of the package, and so won't be installed
11095 by <prgn>dpkg</prgn> when the package is unpacked.
11096 </p>
11099 When you've prepared the package, you should invoke:
11100 <example>
11101 dpkg --build <var>directory</var>
11102 </example>
11103 </p>
11106 This will build the package in
11107 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
11108 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
11109 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
11110 build the package.)
11111 </p>
11114 See the man page <manref name="dpkg-deb" section="8"> for details of how
11115 to examine the contents of this newly-created file. You may find the
11116 output of following commands enlightening:
11117 <example>
11118 dpkg-deb --info <var>filename</var>.deb
11119 dpkg-deb --contents <var>filename</var>.deb
11120 dpkg --contents <var>filename</var>.deb
11121 </example>
11122 To view the copyright file for a package you could use this command:
11123 <example>
11124 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
11125 </example>
11126 </p>
11127 </sect>
11129 <sect id="pkg-controlarea">
11130 <heading>Package control information files</heading>
11133 The control information portion of a binary package is a
11134 collection of files with names known to <prgn>dpkg</prgn>.
11135 It will treat the contents of these files specially - some
11136 of them contain information used by <prgn>dpkg</prgn> when
11137 installing or removing the package; others are scripts which
11138 the package maintainer wants <prgn>dpkg</prgn> to run.
11139 </p>
11142 It is possible to put other files in the package control
11143 information file area, but this is not generally a good idea
11144 (though they will largely be ignored).
11145 </p>
11148 Here is a brief list of the control information files supported
11149 by <prgn>dpkg</prgn> and a summary of what they're used for.
11150 </p>
11153 <taglist>
11154 <tag><tt>control</tt>
11155 <item>
11157 This is the key description file used by
11158 <prgn>dpkg</prgn>. It specifies the package's name
11159 and version, gives its description for the user,
11160 states its relationships with other packages, and so
11161 forth. See <ref id="sourcecontrolfiles"> and
11162 <ref id="binarycontrolfiles">.
11163 </p>
11166 It is usually generated automatically from information
11167 in the source package by the
11168 <prgn>dpkg-gencontrol</prgn> program, and with
11169 assistance from <prgn>dpkg-shlibdeps</prgn>.
11170 See <ref id="pkg-sourcetools">.
11171 </p>
11172 </item>
11174 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
11175 <tt>prerm</tt>
11176 </tag>
11177 <item>
11179 These are executable files (usually scripts) which
11180 <prgn>dpkg</prgn> runs during installation, upgrade
11181 and removal of packages. They allow the package to
11182 deal with matters which are particular to that package
11183 or require more complicated processing than that
11184 provided by <prgn>dpkg</prgn>. Details of when and
11185 how they are called are in <ref id="maintainerscripts">.
11186 </p>
11189 It is very important to make these scripts idempotent.
11190 See <ref id="idempotency">.
11191 </p>
11194 The maintainer scripts are not guaranteed to run with a
11195 controlling terminal and may not be able to interact with
11196 the user. See <ref id="controllingterminal">.
11197 </p>
11198 </item>
11200 <tag><tt>conffiles</tt>
11201 </tag>
11202 <item>
11203 This file contains a list of configuration files which
11204 are to be handled automatically by <prgn>dpkg</prgn>
11205 (see <ref id="pkg-conffiles">). Note that not necessarily
11206 every configuration file should be listed here.
11207 </item>
11209 <tag><tt>shlibs</tt>
11210 </tag>
11211 <item>
11212 This file contains a list of the shared libraries
11213 supplied by the package, with dependency details for
11214 each. This is used by <prgn>dpkg-shlibdeps</prgn>
11215 when it determines what dependencies are required in a
11216 package control file. The <tt>shlibs</tt> file format
11217 is described on <ref id="shlibs">.
11218 </item>
11219 </taglist>
11220 </p>
11222 <sect id="pkg-controlfile">
11223 <heading>The main control information file: <tt>control</tt></heading>
11226 The most important control information file used by
11227 <prgn>dpkg</prgn> when it installs a package is
11228 <tt>control</tt>. It contains all the package's "vital
11229 statistics".
11230 </p>
11233 The binary package control files of packages built from
11234 Debian sources are made by a special tool,
11235 <prgn>dpkg-gencontrol</prgn>, which reads
11236 <file>debian/control</file> and <file>debian/changelog</file> to
11237 find the information it needs. See <ref id="pkg-sourcepkg"> for
11238 more details.
11239 </p>
11242 The fields in binary package control files are listed in
11243 <ref id="binarycontrolfiles">.
11244 </p>
11247 A description of the syntax of control files and the purpose
11248 of the fields is available in <ref id="controlfields">.
11249 </p>
11250 </sect>
11252 <sect>
11253 <heading>Time Stamps</heading>
11256 See <ref id="timestamps">.
11257 </p>
11258 </sect>
11259 </appendix>
11261 <appendix id="pkg-sourcepkg">
11262 <heading>Source packages (from old Packaging Manual) </heading>
11265 The Debian binary packages in the distribution are generated
11266 from Debian sources, which are in a special format to assist
11267 the easy and automatic building of binaries.
11268 </p>
11270 <sect id="pkg-sourcetools">
11271 <heading>Tools for processing source packages</heading>
11274 Various tools are provided for manipulating source packages;
11275 they pack and unpack sources and help build of binary
11276 packages and help manage the distribution of new versions.
11277 </p>
11280 They are introduced and typical uses described here; see
11281 <manref name="dpkg-source" section="1"> for full
11282 documentation about their arguments and operation.
11283 </p>
11286 For examples of how to construct a Debian source package,
11287 and how to use those utilities that are used by Debian
11288 source packages, please see the <prgn>hello</prgn> example
11289 package.
11290 </p>
11292 <sect1 id="pkg-dpkg-source">
11293 <heading>
11294 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
11295 packages
11296 </heading>
11299 This program is frequently used by hand, and is also
11300 called from package-independent automated building scripts
11301 such as <prgn>dpkg-buildpackage</prgn>.
11302 </p>
11305 To unpack a package it is typically invoked with
11306 <example>
11307 dpkg-source -x <var>.../path/to/filename</var>.dsc
11308 </example>
11309 </p>
11312 with the <file><var>filename</var>.tar.gz</file> and
11313 <file><var>filename</var>.diff.gz</file> (if applicable) in
11314 the same directory. It unpacks into
11315 <file><var>package</var>-<var>version</var></file>, and if
11316 applicable
11317 <file><var>package</var>-<var>version</var>.orig</file>, in
11318 the current directory.
11319 </p>
11322 To create a packed source archive it is typically invoked:
11323 <example>
11324 dpkg-source -b <var>package</var>-<var>version</var>
11325 </example>
11326 </p>
11329 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
11330 <file>.diff.gz</file> (if appropriate) in the current
11331 directory. <prgn>dpkg-source</prgn> does not clean the
11332 source tree first - this must be done separately if it is
11333 required.
11334 </p>
11337 See also <ref id="pkg-sourcearchives">.</p>
11338 </sect1>
11341 <sect1 id="pkg-dpkg-buildpackage">
11342 <heading>
11343 <prgn>dpkg-buildpackage</prgn> - overall package-building
11344 control script
11345 </heading>
11348 See <manref name="dpkg-buildpackage" section="1">.
11349 </p>
11350 </sect1>
11352 <sect1 id="pkg-dpkg-gencontrol">
11353 <heading>
11354 <prgn>dpkg-gencontrol</prgn> - generates binary package
11355 control files
11356 </heading>
11359 This program is usually called from <file>debian/rules</file>
11360 (see <ref id="pkg-sourcetree">) in the top level of the source
11361 tree.
11362 </p>
11365 This is usually done just before the files and directories in the
11366 temporary directory tree where the package is being built have their
11367 permissions and ownerships set and the package is constructed using
11368 <prgn>dpkg-deb/</prgn>
11369 <footnote>
11370 This is so that the control file which is produced has
11371 the right permissions
11372 </footnote>.
11373 </p>
11376 <prgn>dpkg-gencontrol</prgn> must be called after all the
11377 files which are to go into the package have been placed in
11378 the temporary build directory, so that its calculation of
11379 the installed size of a package is correct.
11380 </p>
11383 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
11384 be run after <prgn>dpkg-shlibdeps</prgn> so that the
11385 variable substitutions created by
11386 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
11387 are available.
11388 </p>
11391 For a package which generates only one binary package, and
11392 which builds it in <file>debian/tmp</file> relative to the top
11393 of the source package, it is usually sufficient to call
11394 <prgn>dpkg-gencontrol</prgn>.
11395 </p>
11398 Sources which build several binaries will typically need
11399 something like:
11400 <example>
11401 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
11402 </example> The <tt>-P</tt> tells
11403 <prgn>dpkg-gencontrol</prgn> that the package is being
11404 built in a non-default directory, and the <tt>-p</tt>
11405 tells it which package's control file should be generated.
11406 </p>
11409 <prgn>dpkg-gencontrol</prgn> also adds information to the
11410 list of files in <file>debian/files</file>, for the benefit of
11411 (for example) a future invocation of
11412 <prgn>dpkg-genchanges</prgn>.</p>
11413 </sect1>
11415 <sect1 id="pkg-dpkg-shlibdeps">
11416 <heading>
11417 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
11418 dependencies
11419 </heading>
11422 See <manref name="dpkg-shlibdeps" section="1">.
11423 </p>
11424 </sect1>
11426 <sect1 id="pkg-dpkg-distaddfile">
11427 <heading>
11428 <prgn>dpkg-distaddfile</prgn> - adds a file to
11429 <file>debian/files</file>
11430 </heading>
11433 Some packages' uploads need to include files other than
11434 the source and binary package files.
11435 </p>
11438 <prgn>dpkg-distaddfile</prgn> adds a file to the
11439 <file>debian/files</file> file so that it will be included in
11440 the <file>.changes</file> file when
11441 <prgn>dpkg-genchanges</prgn> is run.
11442 </p>
11445 It is usually invoked from the <tt>binary</tt> target of
11446 <file>debian/rules</file>:
11447 <example>
11448 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
11449 </example>
11450 The <var>filename</var> is relative to the directory where
11451 <prgn>dpkg-genchanges</prgn> will expect to find it - this
11452 is usually the directory above the top level of the source
11453 tree. The <file>debian/rules</file> target should put the
11454 file there just before or just after calling
11455 <prgn>dpkg-distaddfile</prgn>.
11456 </p>
11459 The <var>section</var> and <var>priority</var> are passed
11460 unchanged into the resulting <file>.changes</file> file.
11461 </p>
11462 </sect1>
11465 <sect1 id="pkg-dpkg-genchanges">
11466 <heading>
11467 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
11468 upload control file
11469 </heading>
11472 See <manref name="dpkg-genchanges" section="1">.
11473 </p>
11474 </sect1>
11476 <sect1 id="pkg-dpkg-parsechangelog">
11477 <heading>
11478 <prgn>dpkg-parsechangelog</prgn> - produces parsed
11479 representation of a changelog
11480 </heading>
11483 See <manref name="dpkg-parsechangelog" section="1">.
11484 </p>
11485 </sect1>
11487 <sect1 id="pkg-dpkg-architecture">
11488 <heading>
11489 <prgn>dpkg-architecture</prgn> - information about the build and
11490 host system
11491 </heading>
11494 See <manref name="dpkg-architecture" section="1">.
11495 </p>
11496 </sect1>
11497 </sect>
11499 <sect id="pkg-sourcetree">
11500 <heading>The Debian package source tree</heading>
11503 The source archive scheme described later is intended to
11504 allow a Debian package source tree with some associated
11505 control information to be reproduced and transported easily.
11506 The Debian package source tree is a version of the original
11507 program with certain files added for the benefit of the
11508 packaging process, and with any other changes required
11509 made to the rest of the source code and installation
11510 scripts.
11511 </p>
11514 The extra files created for Debian are in the subdirectory
11515 <file>debian</file> of the top level of the Debian package
11516 source tree. They are described below.
11517 </p>
11519 <sect1 id="pkg-debianrules">
11520 <heading><file>debian/rules</file> - the main building script</heading>
11523 See <ref id="debianrules">.
11524 </p>
11525 </sect1>
11527 <sect1 id="pkg-srcsubstvars">
11528 <heading><file>debian/substvars</file> and variable substitutions</heading>
11531 See <ref id="substvars">.
11532 </p>
11534 </sect1>
11536 <sect1>
11537 <heading><file>debian/files</file></heading>
11540 See <ref id="debianfiles">.
11541 </p>
11542 </sect1>
11544 <sect1><heading><file>debian/tmp</file>
11545 </heading>
11548 This is the canonical temporary location for the
11549 construction of binary packages by the <tt>binary</tt>
11550 target. The directory <file>tmp</file> serves as the root of
11551 the file system tree as it is being constructed (for
11552 example, by using the package's upstream makefiles install
11553 targets and redirecting the output there), and it also
11554 contains the <tt>DEBIAN</tt> subdirectory. See <ref
11555 id="pkg-bincreating">.
11556 </p>
11559 If several binary packages are generated from the same
11560 source tree it is usual to use several
11561 <file>debian/tmp<var>something</var></file> directories, for
11562 example <file>tmp-a</file> or <file>tmp-doc</file>.
11563 </p>
11566 Whatever <file>tmp</file> directories are created and used by
11567 <tt>binary</tt> must of course be removed by the
11568 <tt>clean</tt> target.</p></sect1>
11569 </sect>
11572 <sect id="pkg-sourcearchives"><heading>Source packages as archives
11573 </heading>
11576 As it exists on the FTP site, a Debian source package
11577 consists of three related files. You must have the right
11578 versions of all three to be able to use them.
11579 </p>
11582 <taglist>
11583 <tag>Debian source control file - <tt>.dsc</tt></tag>
11584 <item>
11585 This file is a control file used by <prgn>dpkg-source</prgn>
11586 to extract a source package.
11587 See <ref id="debiansourcecontrolfiles">.
11588 </item>
11590 <tag>
11591 Original source archive -
11592 <file>
11593 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
11594 </file>
11595 </tag>
11597 <item>
11599 This is a compressed (with <tt>gzip -9</tt>)
11600 <prgn>tar</prgn> file containing the source code from
11601 the upstream authors of the program.
11602 </p>
11603 </item>
11605 <tag>
11606 Debian package diff -
11607 <file>
11608 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
11609 </file>
11610 </tag>
11611 <item>
11614 This is a unified context diff (<tt>diff -u</tt>)
11615 giving the changes which are required to turn the
11616 original source into the Debian source. These changes
11617 may only include editing and creating plain files.
11618 The permissions of files, the targets of symbolic
11619 links and the characteristics of special files or
11620 pipes may not be changed and no files may be removed
11621 or renamed.
11622 </p>
11625 All the directories in the diff must exist, except the
11626 <file>debian</file> subdirectory of the top of the source
11627 tree, which will be created by
11628 <prgn>dpkg-source</prgn> if necessary when unpacking.
11629 </p>
11632 The <prgn>dpkg-source</prgn> program will
11633 automatically make the <file>debian/rules</file> file
11634 executable (see below).</p></item>
11635 </taglist>
11636 </p>
11639 If there is no original source code - for example, if the
11640 package is specially prepared for Debian or the Debian
11641 maintainer is the same as the upstream maintainer - the
11642 format is slightly different: then there is no diff, and the
11643 tarfile is named
11644 <file><var>package</var>_<var>version</var>.tar.gz</file>,
11645 and preferably contains a directory named
11646 <file><var>package</var>-<var>version</var></file>.
11647 </p>
11648 </sect>
11650 <sect>
11651 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
11654 <tt>dpkg-source -x</tt> is the recommended way to unpack a
11655 Debian source package. However, if it is not available it
11656 is possible to unpack a Debian source archive as follows:
11657 <enumlist compact="compact">
11658 <item>
11660 Untar the tarfile, which will create a <file>.orig</file>
11661 directory.</p>
11662 </item>
11663 <item>
11664 <p>Rename the <file>.orig</file> directory to
11665 <file><var>package</var>-<var>version</var></file>.</p>
11666 </item>
11667 <item>
11669 Create the subdirectory <file>debian</file> at the top of
11670 the source tree.</p>
11671 </item>
11672 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
11673 </item>
11674 <item><p>Untar the tarfile again if you want a copy of the original
11675 source code alongside the Debian version.</p>
11676 </item>
11677 </enumlist>
11680 It is not possible to generate a valid Debian source archive
11681 without using <prgn>dpkg-source</prgn>. In particular,
11682 attempting to use <prgn>diff</prgn> directly to generate the
11683 <file>.diff.gz</file> file will not work.
11684 </p>
11686 <sect1>
11687 <heading>Restrictions on objects in source packages</heading>
11690 The source package may not contain any hard links
11691 <footnote>
11692 This is not currently detected when building source
11693 packages, but only when extracting
11694 them.
11695 </footnote>
11696 <footnote>
11697 Hard links may be permitted at some point in the
11698 future, but would require a fair amount of
11699 work.
11700 </footnote>, device special files, sockets or setuid or
11701 setgid files.
11702 <footnote>
11703 Setgid directories are allowed.
11704 </footnote>
11705 </p>
11708 The source packaging tools manage the changes between the
11709 original and Debian source using <prgn>diff</prgn> and
11710 <prgn>patch</prgn>. Turning the original source tree as
11711 included in the <file>.orig.tar.gz</file> into the Debian
11712 package source must not involve any changes which cannot be
11713 handled by these tools. Problematic changes which cause
11714 <prgn>dpkg-source</prgn> to halt with an error when
11715 building the source package are:
11716 <list compact="compact">
11717 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
11718 </item>
11719 <item><p>Changing the targets of symbolic links.</p>
11720 </item>
11721 <item><p>Creating directories, other than <file>debian</file>.</p>
11722 </item>
11723 <item><p>Changes to the contents of binary files.</p></item>
11724 </list> Changes which cause <prgn>dpkg-source</prgn> to
11725 print a warning but continue anyway are:
11726 <list compact="compact">
11727 <item>
11729 Removing files, directories or symlinks.
11730 <footnote>
11731 Renaming a file is not treated specially - it is
11732 seen as the removal of the old file (which
11733 generates a warning, but is otherwise ignored),
11734 and the creation of the new one.
11735 </footnote>
11736 </p>
11737 </item>
11738 <item>
11740 Changed text files which are missing the usual final
11741 newline (either in the original or the modified
11742 source tree).
11743 </p>
11744 </item>
11745 </list>
11746 Changes which are not represented, but which are not detected by
11747 <prgn>dpkg-source</prgn>, are:
11748 <list compact="compact">
11749 <item><p>Changing the permissions of files (other than
11750 <file>debian/rules</file>) and directories.</p></item>
11751 </list>
11752 </p>
11755 The <file>debian</file> directory and <file>debian/rules</file>
11756 are handled specially by <prgn>dpkg-source</prgn> - before
11757 applying the changes it will create the <file>debian</file>
11758 directory, and afterwards it will make
11759 <file>debian/rules</file> world-executable.
11760 </p>
11761 </sect1>
11762 </sect>
11763 </appendix>
11765 <appendix id="pkg-controlfields">
11766 <heading>Control files and their fields (from old Packaging Manual)</heading>
11769 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
11770 data in a common format, known as control files. Binary and
11771 source packages have control data as do the <file>.changes</file>
11772 files which control the installation of uploaded files, and
11773 <prgn>dpkg</prgn>'s internal databases are in a similar
11774 format.
11775 </p>
11777 <sect>
11778 <heading>Syntax of control files</heading>
11781 See <ref id="controlsyntax">.
11782 </p>
11785 It is important to note that there are several fields which
11786 are optional as far as <prgn>dpkg</prgn> and the related
11787 tools are concerned, but which must appear in every Debian
11788 package, or whose omission may cause problems.
11789 </p>
11790 </sect>
11792 <sect>
11793 <heading>List of fields</heading>
11796 See <ref id="controlfieldslist">.
11797 </p>
11800 This section now contains only the fields that didn't belong
11801 to the Policy manual.
11802 </p>
11804 <sect1 id="pkg-f-Filename">
11805 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
11808 These fields in <tt>Packages</tt> files give the
11809 filename(s) of (the parts of) a package in the
11810 distribution directories, relative to the root of the
11811 Debian hierarchy. If the package has been split into
11812 several parts the parts are all listed in order, separated
11813 by spaces.
11814 </p>
11815 </sect1>
11817 <sect1 id="pkg-f-Size">
11818 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
11821 These fields in <file>Packages</file> files give the size (in
11822 bytes, expressed in decimal) and MD5 checksum of the
11823 file(s) which make(s) up a binary package in the
11824 distribution. If the package is split into several parts
11825 the values for the parts are listed in order, separated by
11826 spaces.
11827 </p>
11828 </sect1>
11830 <sect1 id="pkg-f-Status">
11831 <heading><tt>Status</tt></heading>
11834 This field in <prgn>dpkg</prgn>'s status file records
11835 whether the user wants a package installed, removed or
11836 left alone, whether it is broken (requiring
11837 re-installation) or not and what its current state on the
11838 system is. Each of these pieces of information is a
11839 single word.
11840 </p>
11841 </sect1>
11843 <sect1 id="pkg-f-Config-Version">
11844 <heading><tt>Config-Version</tt></heading>
11847 If a package is not installed or not configured, this
11848 field in <prgn>dpkg</prgn>'s status file records the last
11849 version of the package which was successfully
11850 configured.
11851 </p>
11852 </sect1>
11854 <sect1 id="pkg-f-Conffiles">
11855 <heading><tt>Conffiles</tt></heading>
11858 This field in <prgn>dpkg</prgn>'s status file contains
11859 information about the automatically-managed configuration
11860 files held by a package. This field should <em>not</em>
11861 appear anywhere in a package!
11862 </p>
11863 </sect1>
11865 <sect1>
11866 <heading>Obsolete fields</heading>
11869 These are still recognized by <prgn>dpkg</prgn> but should
11870 not appear anywhere any more.
11872 <taglist compact="compact">
11874 <tag><tt>Revision</tt></tag>
11875 <tag><tt>Package-Revision</tt></tag>
11876 <tag><tt>Package_Revision</tt></tag>
11877 <item>
11878 The Debian revision part of the package version was
11879 at one point in a separate control field. This
11880 field went through several names.
11881 </item>
11883 <tag><tt>Recommended</tt></tag>
11884 <item>Old name for <tt>Recommends</tt>.</item>
11886 <tag><tt>Optional</tt></tag>
11887 <item>Old name for <tt>Suggests</tt>.</item>
11889 <tag><tt>Class</tt></tag>
11890 <item>Old name for <tt>Priority</tt>.</item>
11892 </taglist>
11893 </p>
11894 </sect1>
11895 </sect>
11897 </appendix>
11899 <appendix id="pkg-conffiles">
11900 <heading>Configuration file handling (from old Packaging Manual)</heading>
11903 <prgn>dpkg</prgn> can do a certain amount of automatic
11904 handling of package configuration files.
11905 </p>
11908 Whether this mechanism is appropriate depends on a number of
11909 factors, but basically there are two approaches to any
11910 particular configuration file.
11911 </p>
11914 The easy method is to ship a best-effort configuration in the
11915 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
11916 handle updates. If the user is unlikely to want to edit the
11917 file, but you need them to be able to without losing their
11918 changes, and a new package with a changed version of the file
11919 is only released infrequently, this is a good approach.
11920 </p>
11923 The hard method is to build the configuration file from
11924 scratch in the <prgn>postinst</prgn> script, and to take the
11925 responsibility for fixing any mistakes made in earlier
11926 versions of the package automatically. This will be
11927 appropriate if the file is likely to need to be different on
11928 each system.
11929 </p>
11931 <sect><heading>Automatic handling of configuration files by
11932 <prgn>dpkg</prgn>
11933 </heading>
11936 A package may contain a control information file called
11937 <tt>conffiles</tt>. This file should be a list of filenames
11938 of configuration files needing automatic handling, separated
11939 by newlines. The filenames should be absolute pathnames,
11940 and the files referred to should actually exist in the
11941 package.
11942 </p>
11945 When a package is upgraded <prgn>dpkg</prgn> will process
11946 the configuration files during the configuration stage,
11947 shortly before it runs the package's <prgn>postinst</prgn>
11948 script,
11949 </p>
11952 For each file it checks to see whether the version of the
11953 file included in the package is the same as the one that was
11954 included in the last version of the package (the one that is
11955 being upgraded from); it also compares the version currently
11956 installed on the system with the one shipped with the last
11957 version.
11958 </p>
11961 If neither the user nor the package maintainer has changed
11962 the file, it is left alone. If one or the other has changed
11963 their version, then the changed version is preferred - i.e.,
11964 if the user edits their file, but the package maintainer
11965 doesn't ship a different version, the user's changes will
11966 stay, silently, but if the maintainer ships a new version
11967 and the user hasn't edited it the new version will be
11968 installed (with an informative message). If both have
11969 changed their version the user is prompted about the problem
11970 and must resolve the differences themselves.
11971 </p>
11974 The comparisons are done by calculating the MD5 message
11975 digests of the files, and storing the MD5 of the file as it
11976 was included in the most recent version of the package.
11977 </p>
11980 When a package is installed for the first time
11981 <prgn>dpkg</prgn> will install the file that comes with it,
11982 unless that would mean overwriting a file already on the
11983 file system.
11984 </p>
11987 However, note that <prgn>dpkg</prgn> will <em>not</em>
11988 replace a conffile that was removed by the user (or by a
11989 script). This is necessary because with some programs a
11990 missing file produces an effect hard or impossible to
11991 achieve in another way, so that a missing file needs to be
11992 kept that way if the user did it.
11993 </p>
11996 Note that a package should <em>not</em> modify a
11997 <prgn>dpkg</prgn>-handled conffile in its maintainer
11998 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
11999 the user confusing and possibly dangerous options for
12000 conffile update when the package is upgraded.</p>
12001 </sect>
12003 <sect><heading>Fully-featured maintainer script configuration
12004 handling
12005 </heading>
12008 For files which contain site-specific information such as
12009 the hostname and networking details and so forth, it is
12010 better to create the file in the package's
12011 <prgn>postinst</prgn> script.
12012 </p>
12015 This will typically involve examining the state of the rest
12016 of the system to determine values and other information, and
12017 may involve prompting the user for some information which
12018 can't be obtained some other way.
12019 </p>
12022 When using this method there are a couple of important
12023 issues which should be considered:
12024 </p>
12027 If you discover a bug in the program which generates the
12028 configuration file, or if the format of the file changes
12029 from one version to the next, you will have to arrange for
12030 the postinst script to do something sensible - usually this
12031 will mean editing the installed configuration file to remove
12032 the problem or change the syntax. You will have to do this
12033 very carefully, since the user may have changed the file,
12034 perhaps to fix the very problem that your script is trying
12035 to deal with - you will have to detect these situations and
12036 deal with them correctly.
12037 </p>
12040 If you do go down this route it's probably a good idea to
12041 make the program that generates the configuration file(s) a
12042 separate program in <file>/usr/sbin</file>, by convention called
12043 <file><var>package</var>config</file> and then run that if
12044 appropriate from the post-installation script. The
12045 <tt><var>package</var>config</tt> program should not
12046 unquestioningly overwrite an existing configuration - if its
12047 mode of operation is geared towards setting up a package for
12048 the first time (rather than any arbitrary reconfiguration
12049 later) you should have it check whether the configuration
12050 already exists, and require a <tt>--force</tt> flag to
12051 overwrite it.</p></sect>
12052 </appendix>
12054 <appendix id="pkg-alternatives"><heading>Alternative versions of
12055 an interface - <prgn>update-alternatives</prgn> (from old
12056 Packaging Manual)
12057 </heading>
12060 When several packages all provide different versions of the
12061 same program or file it is useful to have the system select a
12062 default, but to allow the system administrator to change it
12063 and have their decisions respected.
12064 </p>
12067 For example, there are several versions of the <prgn>vi</prgn>
12068 editor, and there is no reason to prevent all of them from
12069 being installed at once, each under their own name
12070 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
12071 Nevertheless it is desirable to have the name <tt>vi</tt>
12072 refer to something, at least by default.
12073 </p>
12076 If all the packages involved cooperate, this can be done with
12077 <prgn>update-alternatives</prgn>.
12078 </p>
12081 Each package provides its own version under its own name, and
12082 calls <prgn>update-alternatives</prgn> in its postinst to
12083 register its version (and again in its prerm to deregister
12084 it).
12085 </p>
12088 See the man page <manref name="update-alternatives"
12089 section="8"> for details.
12090 </p>
12093 If <prgn>update-alternatives</prgn> does not seem appropriate
12094 you may wish to consider using diversions instead.</p>
12095 </appendix>
12097 <appendix id="pkg-diversions"><heading>Diversions - overriding a
12098 package's version of a file (from old Packaging Manual)
12099 </heading>
12102 It is possible to have <prgn>dpkg</prgn> not overwrite a file
12103 when it reinstalls the package it belongs to, and to have it
12104 put the file from the package somewhere else instead.
12105 </p>
12108 This can be used locally to override a package's version of a
12109 file, or by one package to override another's version (or
12110 provide a wrapper for it).
12111 </p>
12114 Before deciding to use a diversion, read <ref
12115 id="pkg-alternatives"> to see if you really want a diversion
12116 rather than several alternative versions of a program.
12117 </p>
12120 There is a diversion list, which is read by <prgn>dpkg</prgn>,
12121 and updated by a special program <prgn>dpkg-divert</prgn>.
12122 Please see <manref name="dpkg-divert" section="8"> for full
12123 details of its operation.
12124 </p>
12127 When a package wishes to divert a file from another, it should
12128 call <prgn>dpkg-divert</prgn> in its preinst to add the
12129 diversion and rename the existing file. For example,
12130 supposing that a <prgn>smailwrapper</prgn> package wishes to
12131 install a wrapper around <file>/usr/sbin/smail</file>:
12132 <example>
12133 dpkg-divert --package smailwrapper --add --rename \
12134 --divert /usr/sbin/smail.real /usr/sbin/smail
12135 </example> The <tt>--package smailwrapper</tt> ensures that
12136 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
12137 can bypass the diversion and get installed as the true version.
12138 It's safe to add the diversion unconditionally on upgrades since
12139 it will be left unchanged if it already exists, but
12140 <prgn>dpkg-divert</prgn> will display a message. To suppress that
12141 message, make the command conditional on the version from which
12142 the package is being upgraded:
12143 <example>
12144 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
12145 dpkg-divert --package smailwrapper --add --rename \
12146 --divert /usr/sbin/smail.real /usr/sbin/smail
12148 </example> where <tt>1.0-2</tt> is the version at which the
12149 diversion was first added to the package. Running the command
12150 during abort-upgrade is pointless but harmless.
12151 </p>
12154 The postrm has to do the reverse:
12155 <example>
12156 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
12157 dpkg-divert --package smailwrapper --remove --rename \
12158 --divert /usr/sbin/smail.real /usr/sbin/smail
12160 </example> If the diversion was added at a particular version, the
12161 postrm should also handle the failure case of upgrading from an
12162 older version (unless the older version is so old that direct
12163 upgrades are no longer supported):
12164 <example>
12165 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
12166 dpkg-divert --package smailwrapper --remove --rename \
12167 --divert /usr/sbin/smail.real /usr/sbin/smail
12169 </example> where <tt>1.0-2</tt> is the version at which the
12170 diversion was first added to the package. The postrm should not
12171 remove the diversion on upgrades both because there's no reason to
12172 remove the diversion only to immediately re-add it and since the
12173 postrm of the old package is run after unpacking so the removal of
12174 the diversion will fail.
12175 </p>
12178 Do not attempt to divert a file which is vitally important for
12179 the system's operation - when using <prgn>dpkg-divert</prgn>
12180 there is a time, after it has been diverted but before
12181 <prgn>dpkg</prgn> has installed the new version, when the file
12182 does not exist.</p>
12185 Do not attempt to divert a conffile, as <prgn>dpkg</prgn> does not
12186 handle it well.
12187 </p>
12188 </appendix>
12190 </book>
12191 </debiandoc>
12192 <!-- Local variables: -->
12193 <!-- indent-tabs-mode: t -->
12194 <!-- End: -->
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