6 @documentencoding UTF-8
7 @settitle GNU Guix Reference Manual
13 Copyright @copyright{} 2012, 2013, 2014, 2015 Ludovic Courtès@*
14 Copyright @copyright{} 2013, 2014 Andreas Enge@*
15 Copyright @copyright{} 2013 Nikita Karetnikov@*
16 Copyright @copyright{} 2015 Mathieu Lirzin@*
17 Copyright @copyright{} 2014 Pierre-Antoine Rault@*
18 Copyright @copyright{} 2015 Taylan Ulrich Bayırlı/Kammer
20 Permission is granted to copy, distribute and/or modify this document
21 under the terms of the GNU Free Documentation License, Version 1.3 or
22 any later version published by the Free Software Foundation; with no
23 Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A
24 copy of the license is included in the section entitled ``GNU Free
25 Documentation License''.
28 @dircategory Package management
30 * guix: (guix). Guix, the functional package manager.
31 * guix package: (guix)Invoking guix package
32 Managing packages with Guix.
33 * guix build: (guix)Invoking guix build
34 Building packages with Guix.
35 * guix system: (guix)Invoking guix system
36 Managing the operating system configuration.
39 @dircategory Software development
41 * guix environment: (guix)Invoking guix environment
42 Building development environments with Guix.
46 @title GNU Guix Reference Manual
47 @subtitle Using the GNU Guix Functional Package Manager
48 @author The GNU Guix Developers
51 @vskip 0pt plus 1filll
52 Edition @value{EDITION} @*
60 @c *********************************************************************
64 This document describes GNU Guix version @value{VERSION}, a functional
65 package management tool written for the GNU system.
68 * Introduction:: What is Guix about?
69 * Installation:: Installing Guix.
70 * Package Management:: Package installation, upgrade, etc.
71 * Emacs Interface:: Using Guix from Emacs.
72 * Programming Interface:: Using Guix in Scheme.
73 * Utilities:: Package management commands.
74 * GNU Distribution:: Software for your friendly GNU system.
75 * Contributing:: Your help needed!
77 * Acknowledgments:: Thanks!
78 * GNU Free Documentation License:: The license of this manual.
79 * Concept Index:: Concepts.
80 * Programming Index:: Data types, functions, and variables.
83 --- The Detailed Node Listing ---
87 * Binary Installation:: Getting Guix running in no time!
88 * Requirements:: Software needed to build and run Guix.
89 * Running the Test Suite:: Testing Guix.
90 * Setting Up the Daemon:: Preparing the build daemon's environment.
91 * Invoking guix-daemon:: Running the build daemon.
92 * Application Setup:: Application-specific setup.
96 * Build Environment Setup:: Preparing the isolated build environment.
97 * Daemon Offload Setup:: Offloading builds to remote machines.
101 * Features:: How Guix will make your life brighter.
102 * Invoking guix package:: Package installation, removal, etc.
103 * Substitutes:: Downloading pre-built binaries.
104 * Packages with Multiple Outputs:: Single source package, multiple outputs.
105 * Invoking guix gc:: Running the garbage collector.
106 * Invoking guix pull:: Fetching the latest Guix and distribution.
107 * Invoking guix archive:: Exporting and importing store files.
111 * Initial Setup: Emacs Initial Setup. Preparing @file{~/.emacs}.
112 * Package Management: Emacs Package Management. Managing packages and generations.
113 * Popup Interface: Emacs Popup Interface. Magit-like interface for guix commands.
114 * Prettify Mode: Emacs Prettify. Abbreviating @file{/gnu/store/@dots{}} file names.
115 * Build Log Mode: Emacs Build Log. Highlighting Guix build logs.
116 * Completions: Emacs Completions. Completing @command{guix} shell command.
117 * Development: Emacs Development. Tools for Guix developers.
119 Programming Interface
121 * Defining Packages:: Defining new packages.
122 * Build Systems:: Specifying how packages are built.
123 * The Store:: Manipulating the package store.
124 * Derivations:: Low-level interface to package derivations.
125 * The Store Monad:: Purely functional interface to the store.
126 * G-Expressions:: Manipulating build expressions.
130 * package Reference:: The package data type.
131 * origin Reference:: The origin data type.
135 * Invoking guix build:: Building packages from the command line.
136 * Invoking guix edit:: Editing package definitions.
137 * Invoking guix download:: Downloading a file and printing its hash.
138 * Invoking guix hash:: Computing the cryptographic hash of a file.
139 * Invoking guix import:: Importing package definitions.
140 * Invoking guix refresh:: Updating package definitions.
141 * Invoking guix lint:: Finding errors in package definitions.
142 * Invoking guix size:: Profiling disk usage.
143 * Invoking guix graph:: Visualizing the graph of packages.
144 * Invoking guix environment:: Setting up development environments.
145 * Invoking guix publish:: Sharing substitutes.
146 * Invoking guix challenge:: Challenging substitute servers.
150 * System Installation:: Installing the whole operating system.
151 * System Configuration:: Configuring the operating system.
152 * Installing Debugging Files:: Feeding the debugger.
153 * Security Updates:: Deploying security fixes quickly.
154 * Package Modules:: Packages from the programmer's viewpoint.
155 * Packaging Guidelines:: Growing the distribution.
156 * Bootstrapping:: GNU/Linux built from scratch.
157 * Porting:: Targeting another platform or kernel.
161 * Using the Configuration System:: Customizing your GNU system.
162 * operating-system Reference:: Detail of operating-system declarations.
163 * File Systems:: Configuring file system mounts.
164 * Mapped Devices:: Block device extra processing.
165 * User Accounts:: Specifying user accounts.
166 * Locales:: Language and cultural convention settings.
167 * Services:: Specifying system services.
168 * Setuid Programs:: Programs running with root privileges.
169 * X.509 Certificates:: Authenticating HTTPS servers.
170 * Name Service Switch:: Configuring libc's name service switch.
171 * Initial RAM Disk:: Linux-Libre bootstrapping.
172 * GRUB Configuration:: Configuring the boot loader.
173 * Invoking guix system:: Instantiating a system configuration.
174 * Defining Services:: Adding new service definitions.
178 * Base Services:: Essential system services.
179 * Networking Services:: Network setup, SSH daemon, etc.
180 * X Window:: Graphical display.
181 * Desktop Services:: D-Bus and desktop services.
182 * Database Services:: SQL databases.
183 * Web Services:: Web servers.
184 * Various Services:: Other services.
188 * Service Composition:: The model for composing services.
189 * Service Types and Services:: Types and services.
190 * Service Reference:: API reference.
191 * dmd Services:: A particular type of service.
195 * Software Freedom:: What may go into the distribution.
196 * Package Naming:: What's in a name?
197 * Version Numbers:: When the name is not enough.
198 * Synopses and Descriptions:: Helping users find the right package.
199 * Python Modules:: Taming the snake.
200 * Perl Modules:: Little pearls.
201 * Fonts:: Fond of fonts.
205 * Building from Git:: The latest and greatest.
206 * Running Guix Before It Is Installed:: Hacker tricks.
207 * The Perfect Setup:: The right tools.
208 * Coding Style:: Hygiene of the contributor.
209 * Submitting Patches:: Share your work.
213 * Programming Paradigm:: How to compose your elements.
214 * Modules:: Where to store your code?
215 * Data Types and Pattern Matching:: Implementing data structures.
216 * Formatting Code:: Writing conventions.
221 @c *********************************************************************
223 @chapter Introduction
225 GNU Guix@footnote{``Guix'' is pronounced like ``geeks'', or ``ɡiːks''
226 using the international phonetic alphabet (IPA).} is a functional
227 package management tool for the GNU system. Package management consists
228 of all activities that relate to building packages from sources,
229 honoring their build-time and run-time dependencies,
230 installing packages in user environments, upgrading installed packages
231 to new versions or rolling back to a previous set, removing unused
232 software packages, etc.
234 @cindex functional package management
235 The term @dfn{functional} refers to a specific package management
236 discipline pioneered by Nix (@pxref{Acknowledgments}).
237 In Guix, the package build and installation process is seen
238 as a function, in the mathematical sense. That function takes inputs,
239 such as build scripts, a compiler, and libraries, and
240 returns an installed package. As a pure function, its result depends
241 solely on its inputs---for instance, it cannot refer to software or
242 scripts that were not explicitly passed as inputs. A build function
243 always produces the same result when passed a given set of inputs. It
244 cannot alter the system's environment in
245 any way; for instance, it cannot create, modify, or delete files outside
246 of its build and installation directories. This is achieved by running
247 build processes in isolated environments (or @dfn{containers}), where only their
248 explicit inputs are visible.
251 The result of package build functions is @dfn{cached} in the file
252 system, in a special directory called @dfn{the store} (@pxref{The
253 Store}). Each package is installed in a directory of its own, in the
254 store---by default under @file{/gnu/store}. The directory name contains
255 a hash of all the inputs used to build that package; thus, changing an
256 input yields a different directory name.
258 This approach is the foundation of Guix's salient features: support for
259 transactional package upgrade and rollback, per-user installation, and
260 garbage collection of packages (@pxref{Features}).
262 Guix has a command-line interface, which allows users to build, install,
263 upgrade, and remove packages, as well as a Scheme programming interface.
265 @cindex Guix System Distribution
267 Last but not least, Guix is used to build a distribution of the GNU
268 system, with many GNU and non-GNU free software packages. The Guix
269 System Distribution, or GNU@tie{}GuixSD, takes advantage of the core
270 properties of Guix at the system level. With GuixSD, users
271 @emph{declare} all aspects of the operating system configuration, and
272 Guix takes care of instantiating that configuration in a reproducible,
273 stateless fashion. @xref{GNU Distribution}.
275 @c *********************************************************************
277 @chapter Installation
279 GNU Guix is available for download from its website at
280 @url{http://www.gnu.org/software/guix/}. This section describes the
281 software requirements of Guix, as well as how to install it and get
284 Note that this section is concerned with the installation of the package
285 manager, which can be done on top of a running GNU/Linux system. If,
286 instead, you want to install the complete GNU operating system,
287 @pxref{System Installation}.
290 * Binary Installation:: Getting Guix running in no time!
291 * Requirements:: Software needed to build and run Guix.
292 * Running the Test Suite:: Testing Guix.
293 * Setting Up the Daemon:: Preparing the build daemon's environment.
294 * Invoking guix-daemon:: Running the build daemon.
295 * Application Setup:: Application-specific setup.
298 @node Binary Installation
299 @section Binary Installation
301 This section describes how to install Guix on an arbitrary system from a
302 self-contained tarball providing binaries for Guix and for all its
303 dependencies. This is often quicker than installing from source, which
304 is described in the next sections. The only requirement is to have
307 Installing goes along these lines:
311 Download the binary tarball from
312 @indicateurl{ftp://alpha.gnu.org/gnu/guix/guix-binary-@value{VERSION}.@var{system}.tar.xz}@footnote{As
313 usual, make sure to download the associated @file{.sig} file and to
314 verify the authenticity of the tarball against it!}, where @var{system}
315 is @code{x86_64-linux} for an @code{x86_64} machine already running the
316 kernel Linux, and so on.
323 # tar --warning=no-timestamp -xf \
324 guix-binary-@value{VERSION}.@var{system}.tar.xz
325 # mv var/guix /var/ && mv gnu /
328 This creates @file{/gnu/store} (@pxref{The Store}) and @file{/var/guix}.
329 The latter contains a ready-to-use profile for @code{root} (see next
332 Do @emph{not} unpack the tarball on a working Guix system since that
333 would overwrite its own essential files.
335 The @code{--warning=no-timestamp} option makes sure GNU@tie{}tar does
336 not emit warnings about ``implausibly old time stamps'' (such
337 warnings were triggered by GNU@tie{}tar 1.26 and older; recent
339 They stem from the fact that all the
340 files in the archive have their modification time set to zero (which
341 means January 1st, 1970.) This is done on purpose to make sure the
342 archive content is independent of its creation time, thus making it
346 Make @code{root}'s profile available under @file{~/.guix-profile}:
349 # ln -sf /var/guix/profiles/per-user/root/guix-profile \
354 Create the group and user accounts for build users as explained below
355 (@pxref{Build Environment Setup}).
361 # ~root/.guix-profile/bin/guix-daemon --build-users-group=guixbuild
364 On hosts using the systemd init system, drop
365 @file{~root/.guix-profile/lib/systemd/system/guix-daemon.service} in
366 @file{/etc/systemd/system}.
369 Make the @command{guix} command available to other users on the machine,
373 # mkdir -p /usr/local/bin
375 # ln -s /var/guix/profiles/per-user/root/guix-profile/bin/guix
379 To use substitutes from @code{hydra.gnu.org} (@pxref{Substitutes}),
383 # guix archive --authorize < ~root/.guix-profile/share/guix/hydra.gnu.org.pub
387 And that's it! For additional tips and tricks, @pxref{Application
390 The @code{guix} package must remain available in @code{root}'s
391 profile, or it would become subject to garbage collection---in which
392 case you would find yourself badly handicapped by the lack of the
393 @command{guix} command.
395 The tarball in question can be (re)produced and verified simply by
396 running the following command in the Guix source tree:
399 make guix-binary.@var{system}.tar.xz
404 @section Requirements
406 This section lists requirements when building Guix from source. The
407 build procedure for Guix is the same as for other GNU software, and is
408 not covered here. Please see the files @file{README} and @file{INSTALL}
409 in the Guix source tree for additional details.
411 GNU Guix depends on the following packages:
414 @item @url{http://gnu.org/software/guile/, GNU Guile}, version 2.0.7 or later;
415 @item @url{http://gnupg.org/, GNU libgcrypt};
416 @item @url{http://www.gnu.org/software/make/, GNU Make}.
419 The following dependencies are optional:
424 @url{http://savannah.nongnu.org/projects/guile-json/, Guile-JSON} will
425 allow you to use the @command{guix import pypi} command (@pxref{Invoking
426 guix import}). It is of
427 interest primarily for developers and not for casual users.
429 Installing @uref{http://gnutls.org/, GnuTLS-Guile} will
430 allow you to access @code{https} URLs with the @command{guix download}
431 command (@pxref{Invoking guix download}), the @command{guix import pypi}
432 command, and the @command{guix import cpan} command. This is primarily
433 of interest to developers. @xref{Guile Preparations, how to install the
434 GnuTLS bindings for Guile,, gnutls-guile, GnuTLS-Guile}.
437 Unless @code{--disable-daemon} was passed to @command{configure}, the
438 following packages are also needed:
441 @item @url{http://sqlite.org, SQLite 3};
442 @item @url{http://www.bzip.org, libbz2};
443 @item @url{http://gcc.gnu.org, GCC's g++}, with support for the
447 When a working installation of @url{http://nixos.org/nix/, the Nix package
448 manager} is available, you
449 can instead configure Guix with @code{--disable-daemon}. In that case,
450 Nix replaces the three dependencies above.
452 Guix is compatible with Nix, so it is possible to share the same store
453 between both. To do so, you must pass @command{configure} not only the
454 same @code{--with-store-dir} value, but also the same
455 @code{--localstatedir} value. The latter is essential because it
456 specifies where the database that stores metadata about the store is
457 located, among other things. The default values for Nix are
458 @code{--with-store-dir=/nix/store} and @code{--localstatedir=/nix/var}.
459 Note that @code{--disable-daemon} is not required if
460 your goal is to share the store with Nix.
462 @node Running the Test Suite
463 @section Running the Test Suite
465 After a successful @command{configure} and @code{make} run, it is a good
466 idea to run the test suite. It can help catch issues with the setup or
467 environment, or bugs in Guix itself---and really, reporting test
468 failures is a good way to help improve the software. To run the test
475 Test cases can run in parallel: you can use the @code{-j} option of
476 GNU@tie{}make to speed things up. The first run may take a few minutes
477 on a recent machine; subsequent runs will be faster because the store
478 that is created for test purposes will already have various things in
481 Upon failure, please email @email{bug-guix@@gnu.org} and attach the
482 @file{test-suite.log} file. When @file{tests/@var{something}.scm}
483 fails, please also attach the @file{@var{something}.log} file available
484 in the top-level build directory. Please specify the Guix version being
485 used as well as version numbers of the dependencies
486 (@pxref{Requirements}) in your message.
488 @node Setting Up the Daemon
489 @section Setting Up the Daemon
492 Operations such as building a package or running the garbage collector
493 are all performed by a specialized process, the @dfn{build daemon}, on
494 behalf of clients. Only the daemon may access the store and its
495 associated database. Thus, any operation that manipulates the store
496 goes through the daemon. For instance, command-line tools such as
497 @command{guix package} and @command{guix build} communicate with the
498 daemon (@i{via} remote procedure calls) to instruct it what to do.
500 The following sections explain how to prepare the build daemon's
501 environment. Also @ref{Substitutes}, for information on how to allow
502 the daemon to download pre-built binaries.
505 * Build Environment Setup:: Preparing the isolated build environment.
506 * Daemon Offload Setup:: Offloading builds to remote machines.
509 @node Build Environment Setup
510 @subsection Build Environment Setup
512 In a standard multi-user setup, Guix and its daemon---the
513 @command{guix-daemon} program---are installed by the system
514 administrator; @file{/gnu/store} is owned by @code{root} and
515 @command{guix-daemon} runs as @code{root}. Unprivileged users may use
516 Guix tools to build packages or otherwise access the store, and the
517 daemon will do it on their behalf, ensuring that the store is kept in a
518 consistent state, and allowing built packages to be shared among users.
521 When @command{guix-daemon} runs as @code{root}, you may not want package
522 build processes themselves to run as @code{root} too, for obvious
523 security reasons. To avoid that, a special pool of @dfn{build users}
524 should be created for use by build processes started by the daemon.
525 These build users need not have a shell and a home directory: they will
526 just be used when the daemon drops @code{root} privileges in build
527 processes. Having several such users allows the daemon to launch
528 distinct build processes under separate UIDs, which guarantees that they
529 do not interfere with each other---an essential feature since builds are
530 regarded as pure functions (@pxref{Introduction}).
532 On a GNU/Linux system, a build user pool may be created like this (using
533 Bash syntax and the @code{shadow} commands):
535 @c See http://lists.gnu.org/archive/html/bug-guix/2013-01/msg00239.html
536 @c for why `-G' is needed.
538 # groupadd --system guixbuild
539 # for i in `seq -w 1 10`;
541 useradd -g guixbuild -G guixbuild \
542 -d /var/empty -s `which nologin` \
543 -c "Guix build user $i" --system \
549 The number of build users determines how many build jobs may run in
550 parallel, as specified by the @option{--max-jobs} option
551 (@pxref{Invoking guix-daemon, @option{--max-jobs}}). The
552 @code{guix-daemon} program may then be run as @code{root} with the
553 following command@footnote{If your machine uses the systemd init system,
554 dropping the @file{@var{prefix}/lib/systemd/system/guix-daemon.service}
555 file in @file{/etc/systemd/system} will ensure that
556 @command{guix-daemon} is automatically started.}:
559 # guix-daemon --build-users-group=guixbuild
564 This way, the daemon starts build processes in a chroot, under one of
565 the @code{guixbuilder} users. On GNU/Linux, by default, the chroot
566 environment contains nothing but:
568 @c Keep this list in sync with libstore/build.cc! -----------------------
571 a minimal @code{/dev} directory, created mostly independently from the
572 host @code{/dev}@footnote{``Mostly'', because while the set of files
573 that appear in the chroot's @code{/dev} is fixed, most of these files
574 can only be created if the host has them.};
577 the @code{/proc} directory; it only shows the container's processes
578 since a separate PID name space is used;
581 @file{/etc/passwd} with an entry for the current user and an entry for
585 @file{/etc/group} with an entry for the user's group;
588 @file{/etc/hosts} with an entry that maps @code{localhost} to
592 a writable @file{/tmp} directory.
595 If you are installing Guix as an unprivileged user, it is still possible
596 to run @command{guix-daemon} provided you pass @code{--disable-chroot}.
597 However, build processes will not be isolated from one another, and not
598 from the rest of the system. Thus, build processes may interfere with
599 each other, and may access programs, libraries, and other files
600 available on the system---making it much harder to view them as
601 @emph{pure} functions.
604 @node Daemon Offload Setup
605 @subsection Using the Offload Facility
609 When desired, the build daemon can @dfn{offload}
610 derivation builds to other machines
611 running Guix, using the @code{offload} @dfn{build hook}. When that
612 feature is enabled, a list of user-specified build machines is read from
613 @file{/etc/guix/machines.scm}; anytime a build is requested, for
614 instance via @code{guix build}, the daemon attempts to offload it to one
615 of the machines that satisfies the derivation's constraints, in
616 particular its system type---e.g., @file{x86_64-linux}. Missing
617 prerequisites for the build are copied over SSH to the target machine,
618 which then proceeds with the build; upon success the output(s) of the
619 build are copied back to the initial machine.
621 The @file{/etc/guix/machines.scm} file typically looks like this:
625 (name "eightysix.example.org")
626 (system "x86_64-linux")
628 (speed 2.)) ; incredibly fast!
631 (name "meeps.example.org")
632 (system "mips64el-linux")
635 (string-append (getenv "HOME")
636 "/.lsh/identity-for-guix"))))
640 In the example above we specify a list of two build machines, one for
641 the @code{x86_64} architecture and one for the @code{mips64el}
644 In fact, this file is---not surprisingly!---a Scheme file that is
645 evaluated when the @code{offload} hook is started. Its return value
646 must be a list of @code{build-machine} objects. While this example
647 shows a fixed list of build machines, one could imagine, say, using
648 DNS-SD to return a list of potential build machines discovered in the
649 local network (@pxref{Introduction, Guile-Avahi,, guile-avahi, Using
650 Avahi in Guile Scheme Programs}). The @code{build-machine} data type is
653 @deftp {Data Type} build-machine
654 This data type represents build machines the daemon may offload builds
655 to. The important fields are:
660 The remote machine's host name.
663 The remote machine's system type---e.g., @code{"x86_64-linux"}.
666 The user account to use when connecting to the remote machine over SSH.
667 Note that the SSH key pair must @emph{not} be passphrase-protected, to
668 allow non-interactive logins.
672 A number of optional fields may be specified:
677 Port number of the machine's SSH server (default: 22).
680 The SSH private key file to use when connecting to the machine.
682 Currently offloading uses GNU@tie{}lsh as its SSH client
683 (@pxref{Invoking lsh,,, GNU lsh Manual}). Thus, the key file here must
684 be an lsh key file. This may change in the future, though.
686 @item parallel-builds
687 The number of builds that may run in parallel on the machine (1 by
691 A ``relative speed factor''. The offload scheduler will tend to prefer
692 machines with a higher speed factor.
695 A list of strings denoting specific features supported by the machine.
696 An example is @code{"kvm"} for machines that have the KVM Linux modules
697 and corresponding hardware support. Derivations can request features by
698 name, and they will be scheduled on matching build machines.
703 The @code{guix} command must be in the search path on the build
704 machines, since offloading works by invoking the @code{guix archive} and
705 @code{guix build} commands. In addition, the Guix modules must be in
706 @code{$GUILE_LOAD_PATH} on the build machine---you can check whether
707 this is the case by running:
710 lsh build-machine guile -c '(use-modules (guix config))'
713 There's one last thing to do once @file{machines.scm} is in place. As
714 explained above, when offloading, files are transferred back and forth
715 between the machine stores. For this to work, you first need to
716 generate a key pair on each machine to allow the daemon to export signed
717 archives of files from the store (@pxref{Invoking guix archive}):
720 # guix archive --generate-key
724 Each build machine must authorize the key of the master machine so that
725 it accepts store items it receives from the master:
728 # guix archive --authorize < master-public-key.txt
732 Likewise, the master machine must authorize the key of each build machine.
734 All the fuss with keys is here to express pairwise mutual trust
735 relations between the master and the build machines. Concretely, when
736 the master receives files from a build machine (and @i{vice versa}), its
737 build daemon can make sure they are genuine, have not been tampered
738 with, and that they are signed by an authorized key.
741 @node Invoking guix-daemon
742 @section Invoking @command{guix-daemon}
744 The @command{guix-daemon} program implements all the functionality to
745 access the store. This includes launching build processes, running the
746 garbage collector, querying the availability of a build result, etc. It
747 is normally run as @code{root} like this:
750 # guix-daemon --build-users-group=guixbuild
754 For details on how to set it up, @pxref{Setting Up the Daemon}.
757 @cindex container, build environment
758 @cindex build environment
759 @cindex reproducible builds
760 By default, @command{guix-daemon} launches build processes under
761 different UIDs, taken from the build group specified with
762 @code{--build-users-group}. In addition, each build process is run in a
763 chroot environment that only contains the subset of the store that the
764 build process depends on, as specified by its derivation
765 (@pxref{Programming Interface, derivation}), plus a set of specific
766 system directories. By default, the latter contains @file{/dev} and
767 @file{/dev/pts}. Furthermore, on GNU/Linux, the build environment is a
768 @dfn{container}: in addition to having its own file system tree, it has
769 a separate mount name space, its own PID name space, network name space,
770 etc. This helps achieve reproducible builds (@pxref{Features}).
772 When the daemon performs a build on behalf of the user, it creates a
773 build directory under @file{/tmp} or under the directory specified by
774 its @code{TMPDIR} environment variable; this directory is shared with
775 the container for the duration of the build. Be aware that using a
776 directory other than @file{/tmp} can affect build results---for example,
777 with a longer directory name, a build process that uses Unix-domain
778 sockets might hit the name length limitation for @code{sun_path}, which
779 it would otherwise not hit.
781 The build directory is automatically deleted upon completion, unless the
782 build failed and the client specified @option{--keep-failed}
783 (@pxref{Invoking guix build, @option{--keep-failed}}).
785 The following command-line options are supported:
788 @item --build-users-group=@var{group}
789 Take users from @var{group} to run build processes (@pxref{Setting Up
790 the Daemon, build users}).
792 @item --no-substitutes
794 Do not use substitutes for build products. That is, always build things
795 locally instead of allowing downloads of pre-built binaries
796 (@pxref{Substitutes}).
798 By default substitutes are used, unless the client---such as the
799 @command{guix package} command---is explicitly invoked with
800 @code{--no-substitutes}.
802 When the daemon runs with @code{--no-substitutes}, clients can still
803 explicitly enable substitution @i{via} the @code{set-build-options}
804 remote procedure call (@pxref{The Store}).
806 @item --substitute-urls=@var{urls}
807 @anchor{daemon-substitute-urls}
808 Consider @var{urls} the default whitespace-separated list of substitute
809 source URLs. When this option is omitted, @indicateurl{http://hydra.gnu.org}
812 This means that substitutes may be downloaded from @var{urls}, as long
813 as they are signed by a trusted signature (@pxref{Substitutes}).
816 @item --no-build-hook
817 Do not use the @dfn{build hook}.
819 The build hook is a helper program that the daemon can start and to
820 which it submits build requests. This mechanism is used to offload
821 builds to other machines (@pxref{Daemon Offload Setup}).
823 @item --cache-failures
824 Cache build failures. By default, only successful builds are cached.
826 When this option is used, @command{guix gc --list-failures} can be used
827 to query the set of store items marked as failed; @command{guix gc
828 --clear-failures} removes store items from the set of cached failures.
829 @xref{Invoking guix gc}.
831 @item --cores=@var{n}
833 Use @var{n} CPU cores to build each derivation; @code{0} means as many
836 The default value is @code{0}, but it may be overridden by clients, such
837 as the @code{--cores} option of @command{guix build} (@pxref{Invoking
840 The effect is to define the @code{NIX_BUILD_CORES} environment variable
841 in the build process, which can then use it to exploit internal
842 parallelism---for instance, by running @code{make -j$NIX_BUILD_CORES}.
844 @item --max-jobs=@var{n}
846 Allow at most @var{n} build jobs in parallel. The default value is
847 @code{1}. Setting it to @code{0} means that no builds will be performed
848 locally; instead, the daemon will offload builds (@pxref{Daemon Offload
849 Setup}), or simply fail.
852 Produce debugging output.
854 This is useful to debug daemon start-up issues, but then it may be
855 overridden by clients, for example the @code{--verbosity} option of
856 @command{guix build} (@pxref{Invoking guix build}).
858 @item --chroot-directory=@var{dir}
859 Add @var{dir} to the build chroot.
861 Doing this may change the result of build processes---for instance if
862 they use optional dependencies found in @var{dir} when it is available,
863 and not otherwise. For that reason, it is not recommended to do so.
864 Instead, make sure that each derivation declares all the inputs that it
867 @item --disable-chroot
868 Disable chroot builds.
870 Using this option is not recommended since, again, it would allow build
871 processes to gain access to undeclared dependencies. It is necessary,
872 though, when @command{guix-daemon} is running under an unprivileged user
875 @item --disable-log-compression
876 Disable compression of the build logs.
878 Unless @code{--lose-logs} is used, all the build logs are kept in the
879 @var{localstatedir}. To save space, the daemon automatically compresses
880 them with bzip2 by default. This option disables that.
882 @item --disable-deduplication
883 @cindex deduplication
884 Disable automatic file ``deduplication'' in the store.
886 By default, files added to the store are automatically ``deduplicated'':
887 if a newly added file is identical to another one found in the store,
888 the daemon makes the new file a hard link to the other file. This can
889 noticeably reduce disk usage, at the expense of slightly increased
890 input/output load at the end of a build process. This option disables
893 @item --gc-keep-outputs[=yes|no]
894 Tell whether the garbage collector (GC) must keep outputs of live
897 When set to ``yes'', the GC will keep the outputs of any live derivation
898 available in the store---the @code{.drv} files. The default is ``no'',
899 meaning that derivation outputs are kept only if they are GC roots.
901 @item --gc-keep-derivations[=yes|no]
902 Tell whether the garbage collector (GC) must keep derivations
903 corresponding to live outputs.
905 When set to ``yes'', as is the case by default, the GC keeps
906 derivations---i.e., @code{.drv} files---as long as at least one of their
907 outputs is live. This allows users to keep track of the origins of
908 items in their store. Setting it to ``no'' saves a bit of disk space.
910 Note that when both @code{--gc-keep-derivations} and
911 @code{--gc-keep-outputs} are used, the effect is to keep all the build
912 prerequisites (the sources, compiler, libraries, and other build-time
913 tools) of live objects in the store, regardless of whether these
914 prerequisites are live. This is convenient for developers since it
915 saves rebuilds or downloads.
917 @item --impersonate-linux-2.6
918 On Linux-based systems, impersonate Linux 2.6. This means that the
919 kernel's @code{uname} system call will report 2.6 as the release number.
921 This might be helpful to build programs that (usually wrongfully) depend
922 on the kernel version number.
925 Do not keep build logs. By default they are kept under
926 @code{@var{localstatedir}/guix/log}.
928 @item --system=@var{system}
929 Assume @var{system} as the current system type. By default it is the
930 architecture/kernel pair found at configure time, such as
933 @item --listen=@var{socket}
934 Listen for connections on @var{socket}, the file name of a Unix-domain
935 socket. The default socket is
936 @file{@var{localstatedir}/daemon-socket/socket}. This option is only
937 useful in exceptional circumstances, such as if you need to run several
938 daemons on the same machine.
942 @node Application Setup
943 @section Application Setup
945 When using Guix on top of GNU/Linux distribution other than GuixSD---a
946 so-called @dfn{foreign distro}---a few additional steps are needed to
947 get everything in place. Here are some of them.
951 @anchor{locales-and-locpath}
952 @cindex locales, when not on GuixSD
955 Packages installed @i{via} Guix will not use the host system's locale
956 data. Instead, you must first install one of the locale packages
957 available with Guix and then define the @code{GUIX_LOCPATH} environment
961 $ guix package -i glibc-locales
962 $ export GUIX_LOCPATH=$HOME/.guix-profile/lib/locale
965 Note that the @code{glibc-locales} package contains data for all the
966 locales supported by the GNU@tie{}libc and weighs in at around
967 110@tie{}MiB. Alternately, the @code{glibc-utf8-locales} is smaller but
968 limited to a few UTF-8 locales.
970 The @code{GUIX_LOCPATH} variable plays a role similar to @code{LOCPATH}
971 (@pxref{Locale Names, @code{LOCPATH},, libc, The GNU C Library Reference
972 Manual}). There are two important differences though:
976 @code{GUIX_LOCPATH} is honored only by Guix's libc, and not by the libc
977 provided by foreign distros. Thus, using @code{GUIX_LOCPATH} allows you
978 to make sure the the foreign distro's programs will not end up loading
979 incompatible locale data.
982 libc suffixes each entry of @code{GUIX_LOCPATH} with @code{/X.Y}, where
983 @code{X.Y} is the libc version---e.g., @code{2.22}. This means that,
984 should your Guix profile contain a mixture of programs linked against
985 different libc version, each libc version will only try to load locale
986 data in the right format.
989 This is important because the locale data format used by different libc
990 versions may be incompatible.
992 @subsection X11 Fonts
994 The majority of graphical applications use Fontconfig to locate and
995 load fonts and perform X11-client-side rendering. Guix's
996 @code{fontconfig} package looks for fonts in @file{$HOME/.guix-profile}
997 by default. Thus, to allow graphical applications installed with Guix
998 to display fonts, you will have to install fonts with Guix as well.
999 Essential font packages include @code{gs-fonts}, @code{font-dejavu}, and
1000 @code{font-gnu-freefont-ttf}.
1004 @c *********************************************************************
1005 @node Package Management
1006 @chapter Package Management
1008 The purpose of GNU Guix is to allow users to easily install, upgrade, and
1009 remove software packages, without having to know about their build
1010 procedure or dependencies. Guix also goes beyond this obvious set of
1013 This chapter describes the main features of Guix, as well as the package
1014 management tools it provides. Two user interfaces are provided for
1015 routine package management tasks: A command-line interface described below
1016 (@pxref{Invoking guix package, @code{guix package}}), as well as a visual user
1017 interface in Emacs described in a subsequent chapter (@pxref{Emacs Interface}).
1020 * Features:: How Guix will make your life brighter.
1021 * Invoking guix package:: Package installation, removal, etc.
1022 * Substitutes:: Downloading pre-built binaries.
1023 * Packages with Multiple Outputs:: Single source package, multiple outputs.
1024 * Invoking guix gc:: Running the garbage collector.
1025 * Invoking guix pull:: Fetching the latest Guix and distribution.
1026 * Invoking guix archive:: Exporting and importing store files.
1032 When using Guix, each package ends up in the @dfn{package store}, in its
1033 own directory---something that resembles
1034 @file{/gnu/store/xxx-package-1.2}, where @code{xxx} is a base32 string
1035 (note that Guix comes with an Emacs extension to shorten those file
1036 names, @pxref{Emacs Prettify}.)
1038 Instead of referring to these directories, users have their own
1039 @dfn{profile}, which points to the packages that they actually want to
1040 use. These profiles are stored within each user's home directory, at
1041 @code{$HOME/.guix-profile}.
1043 For example, @code{alice} installs GCC 4.7.2. As a result,
1044 @file{/home/alice/.guix-profile/bin/gcc} points to
1045 @file{/gnu/store/@dots{}-gcc-4.7.2/bin/gcc}. Now, on the same machine,
1046 @code{bob} had already installed GCC 4.8.0. The profile of @code{bob}
1047 simply continues to point to
1048 @file{/gnu/store/@dots{}-gcc-4.8.0/bin/gcc}---i.e., both versions of GCC
1049 coexist on the same system without any interference.
1051 The @command{guix package} command is the central tool to manage
1052 packages (@pxref{Invoking guix package}). It operates on those per-user
1053 profiles, and can be used @emph{with normal user privileges}.
1055 The command provides the obvious install, remove, and upgrade
1056 operations. Each invocation is actually a @emph{transaction}: either
1057 the specified operation succeeds, or nothing happens. Thus, if the
1058 @command{guix package} process is terminated during the transaction,
1059 or if a power outage occurs during the transaction, then the user's
1060 profile remains in its previous state, and remains usable.
1062 In addition, any package transaction may be @emph{rolled back}. So, if,
1063 for example, an upgrade installs a new version of a package that turns
1064 out to have a serious bug, users may roll back to the previous instance
1065 of their profile, which was known to work well. Similarly, the global
1066 system configuration is subject to transactional upgrades and roll-back
1067 (@pxref{Using the Configuration System}).
1069 All those packages in the package store may be @emph{garbage-collected}.
1070 Guix can determine which packages are still referenced by the user
1071 profiles, and remove those that are provably no longer referenced
1072 (@pxref{Invoking guix gc}). Users may also explicitly remove old
1073 generations of their profile so that the packages they refer to can be
1076 @cindex reproducibility
1077 @cindex reproducible builds
1078 Finally, Guix takes a @dfn{purely functional} approach to package
1079 management, as described in the introduction (@pxref{Introduction}).
1080 Each @file{/gnu/store} package directory name contains a hash of all the
1081 inputs that were used to build that package---compiler, libraries, build
1082 scripts, etc. This direct correspondence allows users to make sure a
1083 given package installation matches the current state of their
1084 distribution. It also helps maximize @dfn{build reproducibility}:
1085 thanks to the isolated build environments that are used, a given build
1086 is likely to yield bit-identical files when performed on different
1087 machines (@pxref{Invoking guix-daemon, container}).
1090 This foundation allows Guix to support @dfn{transparent binary/source
1091 deployment}. When a pre-built binary for a @file{/gnu/store} item is
1092 available from an external source---a @dfn{substitute}, Guix just
1093 downloads it and unpacks it;
1094 otherwise, it builds the package from source, locally
1095 (@pxref{Substitutes}).
1097 Control over the build environment is a feature that is also useful for
1098 developers. The @command{guix environment} command allows developers of
1099 a package to quickly set up the right development environment for their
1100 package, without having to manually install the package's dependencies
1101 in their profile (@pxref{Invoking guix environment}).
1103 @node Invoking guix package
1104 @section Invoking @command{guix package}
1106 The @command{guix package} command is the tool that allows users to
1107 install, upgrade, and remove packages, as well as rolling back to
1108 previous configurations. It operates only on the user's own profile,
1109 and works with normal user privileges (@pxref{Features}). Its syntax
1113 guix package @var{options}
1116 Primarily, @var{options} specifies the operations to be performed during
1117 the transaction. Upon completion, a new profile is created, but
1118 previous @dfn{generations} of the profile remain available, should the user
1121 For example, to remove @code{lua} and install @code{guile} and
1122 @code{guile-cairo} in a single transaction:
1125 guix package -r lua -i guile guile-cairo
1128 @command{guix package} also supports a @dfn{declarative approach}
1129 whereby the user specifies the exact set of packages to be available and
1130 passes it @i{via} the @option{--manifest} option
1131 (@pxref{profile-manifest, @option{--manifest}}).
1133 For each user, a symlink to the user's default profile is automatically
1134 created in @file{$HOME/.guix-profile}. This symlink always points to the
1135 current generation of the user's default profile. Thus, users can add
1136 @file{$HOME/.guix-profile/bin} to their @code{PATH} environment
1137 variable, and so on.
1138 @cindex search paths
1139 If you are not using the Guix System Distribution, consider adding the
1140 following lines to your @file{~/.bash_profile} (@pxref{Bash Startup
1141 Files,,, bash, The GNU Bash Reference Manual}) so that newly-spawned
1142 shells get all the right environment variable definitions:
1145 GUIX_PROFILE="$HOME/.guix-profile" \
1146 source "$HOME/.guix-profile/etc/profile"
1149 In a multi-user setup, user profiles are stored in a place registered as
1150 a @dfn{garbage-collector root}, which @file{$HOME/.guix-profile} points
1151 to (@pxref{Invoking guix gc}). That directory is normally
1152 @code{@var{localstatedir}/profiles/per-user/@var{user}}, where
1153 @var{localstatedir} is the value passed to @code{configure} as
1154 @code{--localstatedir}, and @var{user} is the user name. The
1155 @file{per-user} directory is created when @command{guix-daemon} is
1156 started, and the @var{user} sub-directory is created by @command{guix
1159 The @var{options} can be among the following:
1163 @item --install=@var{package} @dots{}
1164 @itemx -i @var{package} @dots{}
1165 Install the specified @var{package}s.
1167 Each @var{package} may specify either a simple package name, such as
1168 @code{guile}, or a package name followed by a hyphen and version number,
1169 such as @code{guile-1.8.8} or simply @code{guile-1.8} (in the latter
1170 case, the newest version prefixed by @code{1.8} is selected.)
1172 If no version number is specified, the
1173 newest available version will be selected. In addition, @var{package}
1174 may contain a colon, followed by the name of one of the outputs of the
1175 package, as in @code{gcc:doc} or @code{binutils-2.22:lib}
1176 (@pxref{Packages with Multiple Outputs}). Packages with a corresponding
1177 name (and optionally version) are searched for among the GNU
1178 distribution modules (@pxref{Package Modules}).
1180 @cindex propagated inputs
1181 Sometimes packages have @dfn{propagated inputs}: these are dependencies
1182 that automatically get installed along with the required package
1183 (@pxref{package-propagated-inputs, @code{propagated-inputs} in
1184 @code{package} objects}, for information about propagated inputs in
1185 package definitions).
1187 @anchor{package-cmd-propagated-inputs}
1188 An example is the GNU MPC library: its C header files refer to those of
1189 the GNU MPFR library, which in turn refer to those of the GMP library.
1190 Thus, when installing MPC, the MPFR and GMP libraries also get installed
1191 in the profile; removing MPC also removes MPFR and GMP---unless they had
1192 also been explicitly installed independently.
1194 Besides, packages sometimes rely on the definition of environment
1195 variables for their search paths (see explanation of
1196 @code{--search-paths} below). Any missing or possibly incorrect
1197 environment variable definitions are reported here.
1199 @c XXX: keep me up-to-date
1200 Finally, when installing a GNU package, the tool reports the
1201 availability of a newer upstream version. In the future, it may provide
1202 the option of installing directly from the upstream version, even if
1203 that version is not yet in the distribution.
1205 @item --install-from-expression=@var{exp}
1207 Install the package @var{exp} evaluates to.
1209 @var{exp} must be a Scheme expression that evaluates to a
1210 @code{<package>} object. This option is notably useful to disambiguate
1211 between same-named variants of a package, with expressions such as
1212 @code{(@@ (gnu packages base) guile-final)}.
1214 Note that this option installs the first output of the specified
1215 package, which may be insufficient when needing a specific output of a
1216 multiple-output package.
1218 @item --install-from-file=@var{file}
1219 @itemx -f @var{file}
1220 Install the package that the code within @var{file} evaluates to.
1222 As an example, @var{file} might contain a definition like this
1223 (@pxref{Defining Packages}):
1226 @verbatiminclude package-hello.scm
1229 Developers may find it useful to include such a @file{package.scm} file
1230 in the root of their project's source tree that can be used to test
1231 development snapshots and create reproducible development environments
1232 (@pxref{Invoking guix environment}).
1234 @item --remove=@var{package} @dots{}
1235 @itemx -r @var{package} @dots{}
1236 Remove the specified @var{package}s.
1238 As for @code{--install}, each @var{package} may specify a version number
1239 and/or output name in addition to the package name. For instance,
1240 @code{-r glibc:debug} would remove the @code{debug} output of
1243 @item --upgrade[=@var{regexp} @dots{}]
1244 @itemx -u [@var{regexp} @dots{}]
1245 Upgrade all the installed packages. If one or more @var{regexp}s are
1246 specified, upgrade only installed packages whose name matches a
1247 @var{regexp}. Also see the @code{--do-not-upgrade} option below.
1249 Note that this upgrades package to the latest version of packages found
1250 in the distribution currently installed. To update your distribution,
1251 you should regularly run @command{guix pull} (@pxref{Invoking guix
1254 @item --do-not-upgrade[=@var{regexp} @dots{}]
1255 When used together with the @code{--upgrade} option, do @emph{not}
1256 upgrade any packages whose name matches a @var{regexp}. For example, to
1257 upgrade all packages in the current profile except those containing the
1258 substring ``emacs'':
1261 $ guix package --upgrade . --do-not-upgrade emacs
1264 @item @anchor{profile-manifest}--manifest=@var{file}
1265 @itemx -m @var{file}
1266 @cindex profile declaration
1267 @cindex profile manifest
1268 Create a new generation of the profile from the manifest object
1269 returned by the Scheme code in @var{file}.
1271 This allows you to @emph{declare} the profile's contents rather than
1272 constructing it through a sequence of @code{--install} and similar
1273 commands. The advantage is that @var{file} can be put under version
1274 control, copied to different machines to reproduce the same profile, and
1277 @c FIXME: Add reference to (guix profile) documentation when available.
1278 @var{file} must return a @dfn{manifest} object, which is roughly a list
1281 @findex packages->manifest
1283 (use-package-modules guile emacs)
1288 ;; Use a specific package output.
1289 (list guile-2.0 "debug")))
1293 Roll back to the previous @dfn{generation} of the profile---i.e., undo
1294 the last transaction.
1296 When combined with options such as @code{--install}, roll back occurs
1297 before any other actions.
1299 When rolling back from the first generation that actually contains
1300 installed packages, the profile is made to point to the @dfn{zeroth
1301 generation}, which contains no files apart from its own meta-data.
1303 Installing, removing, or upgrading packages from a generation that has
1304 been rolled back to overwrites previous future generations. Thus, the
1305 history of a profile's generations is always linear.
1307 @item --switch-generation=@var{pattern}
1308 @itemx -S @var{pattern}
1309 Switch to a particular generation defined by @var{pattern}.
1311 @var{pattern} may be either a generation number or a number prefixed
1312 with ``+'' or ``-''. The latter means: move forward/backward by a
1313 specified number of generations. For example, if you want to return to
1314 the latest generation after @code{--roll-back}, use
1315 @code{--switch-generation=+1}.
1317 The difference between @code{--roll-back} and
1318 @code{--switch-generation=-1} is that @code{--switch-generation} will
1319 not make a zeroth generation, so if a specified generation does not
1320 exist, the current generation will not be changed.
1322 @item --search-paths[=@var{kind}]
1323 @cindex search paths
1324 Report environment variable definitions, in Bash syntax, that may be
1325 needed in order to use the set of installed packages. These environment
1326 variables are used to specify @dfn{search paths} for files used by some
1327 of the installed packages.
1329 For example, GCC needs the @code{CPATH} and @code{LIBRARY_PATH}
1330 environment variables to be defined so it can look for headers and
1331 libraries in the user's profile (@pxref{Environment Variables,,, gcc,
1332 Using the GNU Compiler Collection (GCC)}). If GCC and, say, the C
1333 library are installed in the profile, then @code{--search-paths} will
1334 suggest setting these variables to @code{@var{profile}/include} and
1335 @code{@var{profile}/lib}, respectively.
1337 The typical use case is to define these environment variables in the
1341 $ eval `guix package --search-paths`
1344 @var{kind} may be one of @code{exact}, @code{prefix}, or @code{suffix},
1345 meaning that the returned environment variable definitions will either
1346 be exact settings, or prefixes or suffixes of the current value of these
1347 variables. When omitted, @var{kind} defaults to @code{exact}.
1349 @item --profile=@var{profile}
1350 @itemx -p @var{profile}
1351 Use @var{profile} instead of the user's default profile.
1354 Produce verbose output. In particular, emit the environment's build log
1355 on the standard error port.
1358 Use the bootstrap Guile to build the profile. This option is only
1359 useful to distribution developers.
1363 In addition to these actions @command{guix package} supports the
1364 following options to query the current state of a profile, or the
1365 availability of packages:
1369 @item --search=@var{regexp}
1370 @itemx -s @var{regexp}
1371 List the available packages whose name, synopsis, or description matches
1372 @var{regexp}. Print all the meta-data of matching packages in
1373 @code{recutils} format (@pxref{Top, GNU recutils databases,, recutils,
1374 GNU recutils manual}).
1376 This allows specific fields to be extracted using the @command{recsel}
1377 command, for instance:
1380 $ guix package -s malloc | recsel -p name,version
1388 Similarly, to show the name of all the packages available under the
1389 terms of the GNU@tie{}LGPL version 3:
1392 $ guix package -s "" | recsel -p name -e 'license ~ "LGPL 3"'
1399 @item --show=@var{package}
1400 Show details about @var{package}, taken from the list of available packages, in
1401 @code{recutils} format (@pxref{Top, GNU recutils databases,, recutils, GNU
1405 $ guix package --show=python | recsel -p name,version
1413 You may also specify the full name of a package to only get details about a
1414 specific version of it:
1416 $ guix package --show=python-3.3.5 | recsel -p name,version
1423 @item --list-installed[=@var{regexp}]
1424 @itemx -I [@var{regexp}]
1425 List the currently installed packages in the specified profile, with the
1426 most recently installed packages shown last. When @var{regexp} is
1427 specified, list only installed packages whose name matches @var{regexp}.
1429 For each installed package, print the following items, separated by
1430 tabs: the package name, its version string, the part of the package that
1431 is installed (for instance, @code{out} for the default output,
1432 @code{include} for its headers, etc.), and the path of this package in
1435 @item --list-available[=@var{regexp}]
1436 @itemx -A [@var{regexp}]
1437 List packages currently available in the distribution for this system
1438 (@pxref{GNU Distribution}). When @var{regexp} is specified, list only
1439 installed packages whose name matches @var{regexp}.
1441 For each package, print the following items separated by tabs: its name,
1442 its version string, the parts of the package (@pxref{Packages with
1443 Multiple Outputs}), and the source location of its definition.
1445 @item --list-generations[=@var{pattern}]
1446 @itemx -l [@var{pattern}]
1447 Return a list of generations along with their creation dates; for each
1448 generation, show the installed packages, with the most recently
1449 installed packages shown last. Note that the zeroth generation is never
1452 For each installed package, print the following items, separated by
1453 tabs: the name of a package, its version string, the part of the package
1454 that is installed (@pxref{Packages with Multiple Outputs}), and the
1455 location of this package in the store.
1457 When @var{pattern} is used, the command returns only matching
1458 generations. Valid patterns include:
1461 @item @emph{Integers and comma-separated integers}. Both patterns denote
1462 generation numbers. For instance, @code{--list-generations=1} returns
1465 And @code{--list-generations=1,8,2} outputs three generations in the
1466 specified order. Neither spaces nor trailing commas are allowed.
1468 @item @emph{Ranges}. @code{--list-generations=2..9} prints the
1469 specified generations and everything in between. Note that the start of
1470 a range must be lesser than its end.
1472 It is also possible to omit the endpoint. For example,
1473 @code{--list-generations=2..}, returns all generations starting from the
1476 @item @emph{Durations}. You can also get the last @emph{N}@tie{}days, weeks,
1477 or months by passing an integer along with the first letter of the
1478 duration. For example, @code{--list-generations=20d} lists generations
1479 that are up to 20 days old.
1482 @item --delete-generations[=@var{pattern}]
1483 @itemx -d [@var{pattern}]
1484 When @var{pattern} is omitted, delete all generations except the current
1487 This command accepts the same patterns as @option{--list-generations}.
1488 When @var{pattern} is specified, delete the matching generations. When
1489 @var{pattern} specifies a duration, generations @emph{older} than the
1490 specified duration match. For instance, @code{--delete-generations=1m}
1491 deletes generations that are more than one month old.
1493 If the current generation matches, it is @emph{not} deleted. Also, the
1494 zeroth generation is never deleted.
1496 Note that deleting generations prevents roll-back to them.
1497 Consequently, this command must be used with care.
1501 Finally, since @command{guix package} may actually start build
1502 processes, it supports all the common build options that @command{guix
1503 build} supports (@pxref{Invoking guix build, common build options}).
1506 @section Substitutes
1509 @cindex pre-built binaries
1510 Guix supports transparent source/binary deployment, which means that it
1511 can either build things locally, or download pre-built items from a
1512 server. We call these pre-built items @dfn{substitutes}---they are
1513 substitutes for local build results. In many cases, downloading a
1514 substitute is much faster than building things locally.
1516 Substitutes can be anything resulting from a derivation build
1517 (@pxref{Derivations}). Of course, in the common case, they are
1518 pre-built package binaries, but source tarballs, for instance, which
1519 also result from derivation builds, can be available as substitutes.
1521 The @code{hydra.gnu.org} server is a front-end to a build farm that
1522 builds packages from the GNU distribution continuously for some
1523 architectures, and makes them available as substitutes. This is the
1524 default source of substitutes; it can be overridden by passing the
1525 @option{--substitute-urls} option either to @command{guix-daemon}
1526 (@pxref{daemon-substitute-urls,, @code{guix-daemon --substitute-urls}})
1527 or to client tools such as @command{guix package}
1528 (@pxref{client-substitute-urls,, client @option{--substitute-urls}
1532 @cindex digital signatures
1533 To allow Guix to download substitutes from @code{hydra.gnu.org}, you
1534 must add its public key to the access control list (ACL) of archive
1535 imports, using the @command{guix archive} command (@pxref{Invoking guix
1536 archive}). Doing so implies that you trust @code{hydra.gnu.org} to not
1537 be compromised and to serve genuine substitutes.
1539 This public key is installed along with Guix, in
1540 @code{@var{prefix}/share/guix/hydra.gnu.org.pub}, where @var{prefix} is
1541 the installation prefix of Guix. If you installed Guix from source,
1542 make sure you checked the GPG signature of
1543 @file{guix-@value{VERSION}.tar.gz}, which contains this public key file.
1544 Then, you can run something like this:
1547 # guix archive --authorize < hydra.gnu.org.pub
1550 Once this is in place, the output of a command like @code{guix build}
1551 should change from something like:
1554 $ guix build emacs --dry-run
1555 The following derivations would be built:
1556 /gnu/store/yr7bnx8xwcayd6j95r2clmkdl1qh688w-emacs-24.3.drv
1557 /gnu/store/x8qsh1hlhgjx6cwsjyvybnfv2i37z23w-dbus-1.6.4.tar.gz.drv
1558 /gnu/store/1ixwp12fl950d15h2cj11c73733jay0z-alsa-lib-1.0.27.1.tar.bz2.drv
1559 /gnu/store/nlma1pw0p603fpfiqy7kn4zm105r5dmw-util-linux-2.21.drv
1567 $ guix build emacs --dry-run
1568 The following files would be downloaded:
1569 /gnu/store/pk3n22lbq6ydamyymqkkz7i69wiwjiwi-emacs-24.3
1570 /gnu/store/2ygn4ncnhrpr61rssa6z0d9x22si0va3-libjpeg-8d
1571 /gnu/store/71yz6lgx4dazma9dwn2mcjxaah9w77jq-cairo-1.12.16
1572 /gnu/store/7zdhgp0n1518lvfn8mb96sxqfmvqrl7v-libxrender-0.9.7
1577 This indicates that substitutes from @code{hydra.gnu.org} are usable and
1578 will be downloaded, when possible, for future builds.
1580 Guix ignores substitutes that are not signed, or that are not signed by
1581 one of the keys listed in the ACL. It also detects and raises an error
1582 when attempting to use a substitute that has been tampered with.
1584 The substitute mechanism can be disabled globally by running
1585 @code{guix-daemon} with @code{--no-substitutes} (@pxref{Invoking
1586 guix-daemon}). It can also be disabled temporarily by passing the
1587 @code{--no-substitutes} option to @command{guix package}, @command{guix
1588 build}, and other command-line tools.
1591 Today, each individual's control over their own computing is at the
1592 mercy of institutions, corporations, and groups with enough power and
1593 determination to subvert the computing infrastructure and exploit its
1594 weaknesses. While using @code{hydra.gnu.org} substitutes can be
1595 convenient, we encourage users to also build on their own, or even run
1596 their own build farm, such that @code{hydra.gnu.org} is less of an
1597 interesting target. One way to help is by publishing the software you
1598 build using @command{guix publish} so that others have one more choice
1599 of server to download substitutes from (@pxref{Invoking guix publish}).
1601 Guix has the foundations to maximize build reproducibility
1602 (@pxref{Features}). In most cases, independent builds of a given
1603 package or derivation should yield bit-identical results. Thus, through
1604 a diverse set of independent package builds, we can strengthen the
1605 integrity of our systems. The @command{guix challenge} command aims to
1606 help users assess substitute servers, and to assist developers in
1607 finding out about non-deterministic package builds (@pxref{Invoking guix
1610 In the future, we want Guix to have support to publish and retrieve
1611 binaries to/from other users, in a peer-to-peer fashion. If you would
1612 like to discuss this project, join us on @email{guix-devel@@gnu.org}.
1615 @node Packages with Multiple Outputs
1616 @section Packages with Multiple Outputs
1618 @cindex multiple-output packages
1619 @cindex package outputs
1621 Often, packages defined in Guix have a single @dfn{output}---i.e., the
1622 source package leads exactly one directory in the store. When running
1623 @command{guix package -i glibc}, one installs the default output of the
1624 GNU libc package; the default output is called @code{out}, but its name
1625 can be omitted as shown in this command. In this particular case, the
1626 default output of @code{glibc} contains all the C header files, shared
1627 libraries, static libraries, Info documentation, and other supporting
1630 Sometimes it is more appropriate to separate the various types of files
1631 produced from a single source package into separate outputs. For
1632 instance, the GLib C library (used by GTK+ and related packages)
1633 installs more than 20 MiB of reference documentation as HTML pages.
1634 To save space for users who do not need it, the documentation goes to a
1635 separate output, called @code{doc}. To install the main GLib output,
1636 which contains everything but the documentation, one would run:
1639 guix package -i glib
1642 The command to install its documentation is:
1645 guix package -i glib:doc
1648 Some packages install programs with different ``dependency footprints''.
1649 For instance, the WordNet package install both command-line tools and
1650 graphical user interfaces (GUIs). The former depend solely on the C
1651 library, whereas the latter depend on Tcl/Tk and the underlying X
1652 libraries. In this case, we leave the command-line tools in the default
1653 output, whereas the GUIs are in a separate output. This allows users
1654 who do not need the GUIs to save space. The @command{guix size} command
1655 can help find out about such situations (@pxref{Invoking guix size}).
1656 @command{guix graph} can also be helpful (@pxref{Invoking guix graph}).
1658 There are several such multiple-output packages in the GNU distribution.
1659 Other conventional output names include @code{lib} for libraries and
1660 possibly header files, @code{bin} for stand-alone programs, and
1661 @code{debug} for debugging information (@pxref{Installing Debugging
1662 Files}). The outputs of a packages are listed in the third column of
1663 the output of @command{guix package --list-available} (@pxref{Invoking
1667 @node Invoking guix gc
1668 @section Invoking @command{guix gc}
1670 @cindex garbage collector
1671 Packages that are installed but not used may be @dfn{garbage-collected}.
1672 The @command{guix gc} command allows users to explicitly run the garbage
1673 collector to reclaim space from the @file{/gnu/store} directory. It is
1674 the @emph{only} way to remove files from @file{/gnu/store}---removing
1675 files or directories manually may break it beyond repair!
1677 The garbage collector has a set of known @dfn{roots}: any file under
1678 @file{/gnu/store} reachable from a root is considered @dfn{live} and
1679 cannot be deleted; any other file is considered @dfn{dead} and may be
1680 deleted. The set of garbage collector roots includes default user
1681 profiles, and may be augmented with @command{guix build --root}, for
1682 example (@pxref{Invoking guix build}).
1684 Prior to running @code{guix gc --collect-garbage} to make space, it is
1685 often useful to remove old generations from user profiles; that way, old
1686 package builds referenced by those generations can be reclaimed. This
1687 is achieved by running @code{guix package --delete-generations}
1688 (@pxref{Invoking guix package}).
1690 The @command{guix gc} command has three modes of operation: it can be
1691 used to garbage-collect any dead files (the default), to delete specific
1692 files (the @code{--delete} option), to print garbage-collector
1693 information, or for more advanced queries. The garbage collection
1694 options are as follows:
1697 @item --collect-garbage[=@var{min}]
1698 @itemx -C [@var{min}]
1699 Collect garbage---i.e., unreachable @file{/gnu/store} files and
1700 sub-directories. This is the default operation when no option is
1703 When @var{min} is given, stop once @var{min} bytes have been collected.
1704 @var{min} may be a number of bytes, or it may include a unit as a
1705 suffix, such as @code{MiB} for mebibytes and @code{GB} for gigabytes
1706 (@pxref{Block size, size specifications,, coreutils, GNU Coreutils}).
1708 When @var{min} is omitted, collect all the garbage.
1712 Attempt to delete all the store files and directories specified as
1713 arguments. This fails if some of the files are not in the store, or if
1714 they are still live.
1716 @item --list-failures
1717 List store items corresponding to cached build failures.
1719 This prints nothing unless the daemon was started with
1720 @option{--cache-failures} (@pxref{Invoking guix-daemon,
1721 @option{--cache-failures}}).
1723 @item --clear-failures
1724 Remove the specified store items from the failed-build cache.
1726 Again, this option only makes sense when the daemon is started with
1727 @option{--cache-failures}. Otherwise, it does nothing.
1730 Show the list of dead files and directories still present in the
1731 store---i.e., files and directories no longer reachable from any root.
1734 Show the list of live store files and directories.
1738 In addition, the references among existing store files can be queried:
1744 List the references (respectively, the referrers) of store files given
1750 List the requisites of the store files passed as arguments. Requisites
1751 include the store files themselves, their references, and the references
1752 of these, recursively. In other words, the returned list is the
1753 @dfn{transitive closure} of the store files.
1755 @xref{Invoking guix size}, for a tool to profile the size of an
1756 element's closure. @xref{Invoking guix graph}, for a tool to visualize
1757 the graph of references.
1761 Lastly, the following options allow you to check the integrity of the
1762 store and to control disk usage.
1766 @item --verify[=@var{options}]
1767 @cindex integrity, of the store
1768 @cindex integrity checking
1769 Verify the integrity of the store.
1771 By default, make sure that all the store items marked as valid in the
1772 daemon's database actually exist in @file{/gnu/store}.
1774 When provided, @var{options} must a comma-separated list containing one
1775 or more of @code{contents} and @code{repair}.
1777 When passing @option{--verify=contents}, the daemon will compute the
1778 content hash of each store item and compare it against its hash in the
1779 database. Hash mismatches are reported as data corruptions. Because it
1780 traverses @emph{all the files in the store}, this command can take a
1781 long time, especially on systems with a slow disk drive.
1783 @cindex repairing the store
1784 Using @option{--verify=repair} or @option{--verify=contents,repair}
1785 causes the daemon to try to repair corrupt store items by fetching
1786 substitutes for them (@pxref{Substitutes}). Because repairing is not
1787 atomic, and thus potentially dangerous, it is available only to the
1788 system administrator.
1791 @cindex deduplication
1792 Optimize the store by hard-linking identical files---this is
1793 @dfn{deduplication}.
1795 The daemon performs deduplication after each successful build or archive
1796 import, unless it was started with @code{--disable-deduplication}
1797 (@pxref{Invoking guix-daemon, @code{--disable-deduplication}}). Thus,
1798 this option is primarily useful when the daemon was running with
1799 @code{--disable-deduplication}.
1803 @node Invoking guix pull
1804 @section Invoking @command{guix pull}
1806 Packages are installed or upgraded to the latest version available in
1807 the distribution currently available on your local machine. To update
1808 that distribution, along with the Guix tools, you must run @command{guix
1809 pull}: the command downloads the latest Guix source code and package
1810 descriptions, and deploys it.
1812 On completion, @command{guix package} will use packages and package
1813 versions from this just-retrieved copy of Guix. Not only that, but all
1814 the Guix commands and Scheme modules will also be taken from that latest
1815 version. New @command{guix} sub-commands added by the update also
1818 The @command{guix pull} command is usually invoked with no arguments,
1819 but it supports the following options:
1823 Produce verbose output, writing build logs to the standard error output.
1825 @item --url=@var{url}
1826 Download the source tarball of Guix from @var{url}.
1828 By default, the tarball is taken from its canonical address at
1829 @code{gnu.org}, for the stable branch of Guix.
1832 Use the bootstrap Guile to build the latest Guix. This option is only
1833 useful to Guix developers.
1837 @node Invoking guix archive
1838 @section Invoking @command{guix archive}
1840 The @command{guix archive} command allows users to @dfn{export} files
1841 from the store into a single archive, and to later @dfn{import} them.
1842 In particular, it allows store files to be transferred from one machine
1843 to another machine's store. For example, to transfer the @code{emacs}
1844 package to a machine connected over SSH, one would run:
1847 guix archive --export -r emacs | ssh the-machine guix archive --import
1851 Similarly, a complete user profile may be transferred from one machine
1852 to another like this:
1855 guix archive --export -r $(readlink -f ~/.guix-profile) | \
1856 ssh the-machine guix-archive --import
1860 However, note that, in both examples, all of @code{emacs} and the
1861 profile as well as all of their dependencies are transferred (due to
1862 @code{-r}), regardless of what is already available in the target
1863 machine's store. The @code{--missing} option can help figure out which
1864 items are missing from the target's store.
1866 Archives are stored in the ``Nix archive'' or ``Nar'' format, which is
1867 comparable in spirit to `tar', but with a few noteworthy differences
1868 that make it more appropriate for our purposes. First, rather than
1869 recording all Unix meta-data for each file, the Nar format only mentions
1870 the file type (regular, directory, or symbolic link); Unix permissions
1871 and owner/group are dismissed. Second, the order in which directory
1872 entries are stored always follows the order of file names according to
1873 the C locale collation order. This makes archive production fully
1876 When exporting, the daemon digitally signs the contents of the archive,
1877 and that digital signature is appended. When importing, the daemon
1878 verifies the signature and rejects the import in case of an invalid
1879 signature or if the signing key is not authorized.
1880 @c FIXME: Add xref to daemon doc about signatures.
1882 The main options are:
1886 Export the specified store files or packages (see below.) Write the
1887 resulting archive to the standard output.
1889 Dependencies are @emph{not} included in the output, unless
1890 @code{--recursive} is passed.
1894 When combined with @code{--export}, this instructs @command{guix
1895 archive} to include dependencies of the given items in the archive.
1896 Thus, the resulting archive is self-contained: it contains the closure
1897 of the exported store items.
1900 Read an archive from the standard input, and import the files listed
1901 therein into the store. Abort if the archive has an invalid digital
1902 signature, or if it is signed by a public key not among the authorized
1903 keys (see @code{--authorize} below.)
1906 Read a list of store file names from the standard input, one per line,
1907 and write on the standard output the subset of these files missing from
1910 @item --generate-key[=@var{parameters}]
1911 @cindex signing, archives
1912 Generate a new key pair for the daemons. This is a prerequisite before
1913 archives can be exported with @code{--export}. Note that this operation
1914 usually takes time, because it needs to gather enough entropy to
1915 generate the key pair.
1917 The generated key pair is typically stored under @file{/etc/guix}, in
1918 @file{signing-key.pub} (public key) and @file{signing-key.sec} (private
1919 key, which must be kept secret.) When @var{parameters} is omitted,
1920 an ECDSA key using the Ed25519 curve is generated, or, for Libgcrypt
1921 versions before 1.6.0, it is a 4096-bit RSA key.
1922 Alternately, @var{parameters} can specify
1923 @code{genkey} parameters suitable for Libgcrypt (@pxref{General
1924 public-key related Functions, @code{gcry_pk_genkey},, gcrypt, The
1925 Libgcrypt Reference Manual}).
1928 @cindex authorizing, archives
1929 Authorize imports signed by the public key passed on standard input.
1930 The public key must be in ``s-expression advanced format''---i.e., the
1931 same format as the @file{signing-key.pub} file.
1933 The list of authorized keys is kept in the human-editable file
1934 @file{/etc/guix/acl}. The file contains
1935 @url{http://people.csail.mit.edu/rivest/Sexp.txt, ``advanced-format
1936 s-expressions''} and is structured as an access-control list in the
1937 @url{http://theworld.com/~cme/spki.txt, Simple Public-Key Infrastructure
1940 @item --extract=@var{directory}
1941 @itemx -x @var{directory}
1942 Read a single-item archive as served by substitute servers
1943 (@pxref{Substitutes}) and extract it to @var{directory}. This is a
1944 low-level operation needed in only very narrow use cases; see below.
1946 For example, the following command extracts the substitute for Emacs
1947 served by @code{hydra.gnu.org} to @file{/tmp/emacs}:
1951 http://hydra.gnu.org/nar/@dots{}-emacs-24.5 \
1952 | bunzip2 | guix archive -x /tmp/emacs
1955 Single-item archives are different from multiple-item archives produced
1956 by @command{guix archive --export}; they contain a single store item,
1957 and they do @emph{not} embed a signature. Thus this operation does
1958 @emph{no} signature verification and its output should be considered
1961 The primary purpose of this operation is to facilitate inspection of
1962 archive contents coming from possibly untrusted substitute servers.
1966 To export store files as an archive to the standard output, run:
1969 guix archive --export @var{options} @var{specifications}...
1972 @var{specifications} may be either store file names or package
1973 specifications, as for @command{guix package} (@pxref{Invoking guix
1974 package}). For instance, the following command creates an archive
1975 containing the @code{gui} output of the @code{git} package and the main
1976 output of @code{emacs}:
1979 guix archive --export git:gui /gnu/store/...-emacs-24.3 > great.nar
1982 If the specified packages are not built yet, @command{guix archive}
1983 automatically builds them. The build process may be controlled with the
1984 same options that can be passed to the @command{guix build} command
1985 (@pxref{Invoking guix build, common build options}).
1987 @c *********************************************************************
1990 @c *********************************************************************
1991 @node Programming Interface
1992 @chapter Programming Interface
1994 GNU Guix provides several Scheme programming interfaces (APIs) to
1995 define, build, and query packages. The first interface allows users to
1996 write high-level package definitions. These definitions refer to
1997 familiar packaging concepts, such as the name and version of a package,
1998 its build system, and its dependencies. These definitions can then be
1999 turned into concrete build actions.
2001 Build actions are performed by the Guix daemon, on behalf of users. In a
2002 standard setup, the daemon has write access to the store---the
2003 @file{/gnu/store} directory---whereas users do not. The recommended
2004 setup also has the daemon perform builds in chroots, under a specific
2005 build users, to minimize interference with the rest of the system.
2008 Lower-level APIs are available to interact with the daemon and the
2009 store. To instruct the daemon to perform a build action, users actually
2010 provide it with a @dfn{derivation}. A derivation is a low-level
2011 representation of the build actions to be taken, and the environment in
2012 which they should occur---derivations are to package definitions what
2013 assembly is to C programs. The term ``derivation'' comes from the fact
2014 that build results @emph{derive} from them.
2016 This chapter describes all these APIs in turn, starting from high-level
2017 package definitions.
2020 * Defining Packages:: Defining new packages.
2021 * Build Systems:: Specifying how packages are built.
2022 * The Store:: Manipulating the package store.
2023 * Derivations:: Low-level interface to package derivations.
2024 * The Store Monad:: Purely functional interface to the store.
2025 * G-Expressions:: Manipulating build expressions.
2028 @node Defining Packages
2029 @section Defining Packages
2031 The high-level interface to package definitions is implemented in the
2032 @code{(guix packages)} and @code{(guix build-system)} modules. As an
2033 example, the package definition, or @dfn{recipe}, for the GNU Hello
2034 package looks like this:
2037 (define-module (gnu packages hello)
2038 #:use-module (guix packages)
2039 #:use-module (guix download)
2040 #:use-module (guix build-system gnu)
2041 #:use-module (guix licenses)
2042 #:use-module (gnu packages gawk))
2044 (define-public hello
2050 (uri (string-append "mirror://gnu/hello/hello-" version
2054 "0ssi1wpaf7plaswqqjwigppsg5fyh99vdlb9kzl7c9lng89ndq1i"))))
2055 (build-system gnu-build-system)
2056 (arguments `(#:configure-flags '("--enable-silent-rules")))
2057 (inputs `(("gawk" ,gawk)))
2058 (synopsis "Hello, GNU world: An example GNU package")
2059 (description "Guess what GNU Hello prints!")
2060 (home-page "http://www.gnu.org/software/hello/")
2065 Without being a Scheme expert, the reader may have guessed the meaning
2066 of the various fields here. This expression binds variable @code{hello}
2067 to a @code{<package>} object, which is essentially a record
2068 (@pxref{SRFI-9, Scheme records,, guile, GNU Guile Reference Manual}).
2069 This package object can be inspected using procedures found in the
2070 @code{(guix packages)} module; for instance, @code{(package-name hello)}
2071 returns---surprise!---@code{"hello"}.
2073 With luck, you may be able to import part or all of the definition of
2074 the package you are interested in from another repository, using the
2075 @code{guix import} command (@pxref{Invoking guix import}).
2077 In the example above, @var{hello} is defined into a module of its own,
2078 @code{(gnu packages hello)}. Technically, this is not strictly
2079 necessary, but it is convenient to do so: all the packages defined in
2080 modules under @code{(gnu packages @dots{})} are automatically known to
2081 the command-line tools (@pxref{Package Modules}).
2083 There are a few points worth noting in the above package definition:
2087 The @code{source} field of the package is an @code{<origin>} object
2088 (@pxref{origin Reference}, for the complete reference).
2089 Here, the @code{url-fetch} method from @code{(guix download)} is used,
2090 meaning that the source is a file to be downloaded over FTP or HTTP.
2092 The @code{mirror://gnu} prefix instructs @code{url-fetch} to use one of
2093 the GNU mirrors defined in @code{(guix download)}.
2095 The @code{sha256} field specifies the expected SHA256 hash of the file
2096 being downloaded. It is mandatory, and allows Guix to check the
2097 integrity of the file. The @code{(base32 @dots{})} form introduces the
2098 base32 representation of the hash. You can obtain this information with
2099 @code{guix download} (@pxref{Invoking guix download}) and @code{guix
2100 hash} (@pxref{Invoking guix hash}).
2103 When needed, the @code{origin} form can also have a @code{patches} field
2104 listing patches to be applied, and a @code{snippet} field giving a
2105 Scheme expression to modify the source code.
2108 @cindex GNU Build System
2109 The @code{build-system} field specifies the procedure to build the
2110 package (@pxref{Build Systems}). Here, @var{gnu-build-system}
2111 represents the familiar GNU Build System, where packages may be
2112 configured, built, and installed with the usual @code{./configure &&
2113 make && make check && make install} command sequence.
2116 The @code{arguments} field specifies options for the build system
2117 (@pxref{Build Systems}). Here it is interpreted by
2118 @var{gnu-build-system} as a request run @file{configure} with the
2119 @code{--enable-silent-rules} flag.
2122 The @code{inputs} field specifies inputs to the build process---i.e.,
2123 build-time or run-time dependencies of the package. Here, we define an
2124 input called @code{"gawk"} whose value is that of the @var{gawk}
2125 variable; @var{gawk} is itself bound to a @code{<package>} object.
2127 Note that GCC, Coreutils, Bash, and other essential tools do not need to
2128 be specified as inputs here. Instead, @var{gnu-build-system} takes care
2129 of ensuring that they are present (@pxref{Build Systems}).
2131 However, any other dependencies need to be specified in the
2132 @code{inputs} field. Any dependency not specified here will simply be
2133 unavailable to the build process, possibly leading to a build failure.
2136 @xref{package Reference}, for a full description of possible fields.
2138 Once a package definition is in place, the
2139 package may actually be built using the @code{guix build} command-line
2140 tool (@pxref{Invoking guix build}). You can easily jump back to the
2141 package definition using the @command{guix edit} command
2142 (@pxref{Invoking guix edit}).
2143 @xref{Packaging Guidelines}, for
2144 more information on how to test package definitions, and
2145 @ref{Invoking guix lint}, for information on how to check a definition
2146 for style conformance.
2148 Eventually, updating the package definition to a new upstream version
2149 can be partly automated by the @command{guix refresh} command
2150 (@pxref{Invoking guix refresh}).
2152 Behind the scenes, a derivation corresponding to the @code{<package>}
2153 object is first computed by the @code{package-derivation} procedure.
2154 That derivation is stored in a @code{.drv} file under @file{/gnu/store}.
2155 The build actions it prescribes may then be realized by using the
2156 @code{build-derivations} procedure (@pxref{The Store}).
2158 @deffn {Scheme Procedure} package-derivation @var{store} @var{package} [@var{system}]
2159 Return the @code{<derivation>} object of @var{package} for @var{system}
2160 (@pxref{Derivations}).
2162 @var{package} must be a valid @code{<package>} object, and @var{system}
2163 must be a string denoting the target system type---e.g.,
2164 @code{"x86_64-linux"} for an x86_64 Linux-based GNU system. @var{store}
2165 must be a connection to the daemon, which operates on the store
2166 (@pxref{The Store}).
2170 @cindex cross-compilation
2171 Similarly, it is possible to compute a derivation that cross-builds a
2172 package for some other system:
2174 @deffn {Scheme Procedure} package-cross-derivation @var{store} @
2175 @var{package} @var{target} [@var{system}]
2176 Return the @code{<derivation>} object of @var{package} cross-built from
2177 @var{system} to @var{target}.
2179 @var{target} must be a valid GNU triplet denoting the target hardware
2180 and operating system, such as @code{"mips64el-linux-gnu"}
2181 (@pxref{Configuration Names, GNU configuration triplets,, configure, GNU
2182 Configure and Build System}).
2186 * package Reference :: The package data type.
2187 * origin Reference:: The origin data type.
2191 @node package Reference
2192 @subsection @code{package} Reference
2194 This section summarizes all the options available in @code{package}
2195 declarations (@pxref{Defining Packages}).
2197 @deftp {Data Type} package
2198 This is the data type representing a package recipe.
2202 The name of the package, as a string.
2204 @item @code{version}
2205 The version of the package, as a string.
2208 An origin object telling how the source code for the package should be
2209 acquired (@pxref{origin Reference}).
2211 @item @code{build-system}
2212 The build system that should be used to build the package (@pxref{Build
2215 @item @code{arguments} (default: @code{'()})
2216 The arguments that should be passed to the build system. This is a
2217 list, typically containing sequential keyword-value pairs.
2219 @item @code{inputs} (default: @code{'()})
2220 Package or derivation inputs to the build. This is a list of lists,
2221 where each list has the name of the input (a string) as its first
2222 element, a package or derivation object as its second element, and
2223 optionally the name of the output of the package or derivation that
2224 should be used, which defaults to @code{"out"}.
2226 @item @anchor{package-propagated-inputs}@code{propagated-inputs} (default: @code{'()})
2227 @cindex propagated inputs
2228 This field is like @code{inputs}, but the specified packages will be
2229 force-installed alongside the package they belong to
2230 (@pxref{package-cmd-propagated-inputs, @command{guix package}}, for
2231 information on how @command{guix package} deals with propagated inputs.)
2233 For example this is necessary when a library needs headers of another
2234 library to compile, or needs another shared library to be linked
2235 alongside itself when a program wants to link to it.
2237 @item @code{native-inputs} (default: @code{'()})
2238 This field is like @code{inputs}, but in case of a cross-compilation it
2239 will be ensured that packages for the architecture of the build machine
2240 are present, such that executables from them can be used during the
2243 This is typically where you would list tools needed at build time but
2244 not at run time, such as Autoconf, Automake, pkg-config, Gettext, or
2245 Bison. @command{guix lint} can report likely mistakes in this area
2246 (@pxref{Invoking guix lint}).
2248 @item @code{self-native-input?} (default: @code{#f})
2249 This is a Boolean field telling whether the package should use itself as
2250 a native input when cross-compiling.
2252 @item @code{outputs} (default: @code{'("out")})
2253 The list of output names of the package. @xref{Packages with Multiple
2254 Outputs}, for typical uses of additional outputs.
2256 @item @code{native-search-paths} (default: @code{'()})
2257 @itemx @code{search-paths} (default: @code{'()})
2258 A list of @code{search-path-specification} objects describing
2259 search-path environment variables honored by the package.
2261 @item @code{replacement} (default: @code{#f})
2262 This must either @code{#f} or a package object that will be used as a
2263 @dfn{replacement} for this package. @xref{Security Updates, grafts},
2266 @item @code{synopsis}
2267 A one-line description of the package.
2269 @item @code{description}
2270 A more elaborate description of the package.
2272 @item @code{license}
2273 The license of the package; a value from @code{(guix licenses)}.
2275 @item @code{home-page}
2276 The URL to the home-page of the package, as a string.
2278 @item @code{supported-systems} (default: @var{%supported-systems})
2279 The list of systems supported by the package, as strings of the form
2280 @code{architecture-kernel}, for example @code{"x86_64-linux"}.
2282 @item @code{maintainers} (default: @code{'()})
2283 The list of maintainers of the package, as @code{maintainer} objects.
2285 @item @code{location} (default: source location of the @code{package} form)
2286 The source location of the package. It's useful to override this when
2287 inheriting from another package, in which case this field is not
2288 automatically corrected.
2293 @node origin Reference
2294 @subsection @code{origin} Reference
2296 This section summarizes all the options available in @code{origin}
2297 declarations (@pxref{Defining Packages}).
2299 @deftp {Data Type} origin
2300 This is the data type representing a source code origin.
2304 An object containing the URI of the source. The object type depends on
2305 the @code{method} (see below). For example, when using the
2306 @var{url-fetch} method of @code{(guix download)}, the valid @code{uri}
2307 values are: a URL represented as a string, or a list thereof.
2310 A procedure that will handle the URI.
2315 @item @var{url-fetch} from @code{(guix download)}
2316 download a file the HTTP, HTTPS, or FTP URL specified in the
2319 @item @var{git-fetch} from @code{(guix git-download)}
2320 clone the Git version control repository, and check out the revision
2321 specified in the @code{uri} field as a @code{git-reference} object; a
2322 @code{git-reference} looks like this:
2326 (url "git://git.debian.org/git/pkg-shadow/shadow")
2327 (commit "v4.1.5.1"))
2332 A bytevector containing the SHA-256 hash of the source. Typically the
2333 @code{base32} form is used here to generate the bytevector from a
2336 @item @code{file-name} (default: @code{#f})
2337 The file name under which the source code should be saved. When this is
2338 @code{#f}, a sensible default value will be used in most cases. In case
2339 the source is fetched from a URL, the file name from the URL will be
2340 used. For version control checkouts, it's recommended to provide the
2341 file name explicitly because the default is not very descriptive.
2343 @item @code{patches} (default: @code{'()})
2344 A list of file names containing patches to be applied to the source.
2346 @item @code{snippet} (default: @code{#f})
2347 A quoted piece of code that will be run in the source directory to make
2348 any modifications, which is sometimes more convenient than a patch.
2350 @item @code{patch-flags} (default: @code{'("-p1")})
2351 A list of command-line flags that should be passed to the @code{patch}
2354 @item @code{patch-inputs} (default: @code{#f})
2355 Input packages or derivations to the patching process. When this is
2356 @code{#f}, the usual set of inputs necessary for patching are provided,
2357 such as GNU@tie{}Patch.
2359 @item @code{modules} (default: @code{'()})
2360 A list of Guile modules that should be loaded during the patching
2361 process and while running the code in the @code{snippet} field.
2363 @item @code{imported-modules} (default: @code{'()})
2364 The list of Guile modules to import in the patch derivation, for use by
2367 @item @code{patch-guile} (default: @code{#f})
2368 The Guile package that should be used in the patching process. When
2369 this is @code{#f}, a sensible default is used.
2375 @section Build Systems
2377 @cindex build system
2378 Each package definition specifies a @dfn{build system} and arguments for
2379 that build system (@pxref{Defining Packages}). This @code{build-system}
2380 field represents the build procedure of the package, as well implicit
2381 dependencies of that build procedure.
2383 Build systems are @code{<build-system>} objects. The interface to
2384 create and manipulate them is provided by the @code{(guix build-system)}
2385 module, and actual build systems are exported by specific modules.
2387 @cindex bag (low-level package representation)
2388 Under the hood, build systems first compile package objects to
2389 @dfn{bags}. A @dfn{bag} is like a package, but with less
2390 ornamentation---in other words, a bag is a lower-level representation of
2391 a package, which includes all the inputs of that package, including some
2392 that were implicitly added by the build system. This intermediate
2393 representation is then compiled to a derivation (@pxref{Derivations}).
2395 Build systems accept an optional list of @dfn{arguments}. In package
2396 definitions, these are passed @i{via} the @code{arguments} field
2397 (@pxref{Defining Packages}). They are typically keyword arguments
2398 (@pxref{Optional Arguments, keyword arguments in Guile,, guile, GNU
2399 Guile Reference Manual}). The value of these arguments is usually
2400 evaluated in the @dfn{build stratum}---i.e., by a Guile process launched
2401 by the daemon (@pxref{Derivations}).
2403 The main build system is @var{gnu-build-system}, which implements the
2404 standard build procedure for GNU packages and many other packages. It
2405 is provided by the @code{(guix build-system gnu)} module.
2407 @defvr {Scheme Variable} gnu-build-system
2408 @var{gnu-build-system} represents the GNU Build System, and variants
2409 thereof (@pxref{Configuration, configuration and makefile conventions,,
2410 standards, GNU Coding Standards}).
2412 @cindex build phases
2413 In a nutshell, packages using it configured, built, and installed with
2414 the usual @code{./configure && make && make check && make install}
2415 command sequence. In practice, a few additional steps are often needed.
2416 All these steps are split up in separate @dfn{phases},
2417 notably@footnote{Please see the @code{(guix build gnu-build-system)}
2418 modules for more details about the build phases.}:
2422 Unpack the source tarball, and change the current directory to the
2423 extracted source tree. If the source is actually a directory, copy it
2424 to the build tree, and enter that directory.
2426 @item patch-source-shebangs
2427 Patch shebangs encountered in source files so they refer to the right
2428 store file names. For instance, this changes @code{#!/bin/sh} to
2429 @code{#!/gnu/store/@dots{}-bash-4.3/bin/sh}.
2432 Run the @file{configure} script with a number of default options, such
2433 as @code{--prefix=/gnu/store/@dots{}}, as well as the options specified
2434 by the @code{#:configure-flags} argument.
2437 Run @code{make} with the list of flags specified with
2438 @code{#:make-flags}. If the @code{#:parallel-builds?} argument is true
2439 (the default), build with @code{make -j}.
2442 Run @code{make check}, or some other target specified with
2443 @code{#:test-target}, unless @code{#:tests? #f} is passed. If the
2444 @code{#:parallel-tests?} argument is true (the default), run @code{make
2448 Run @code{make install} with the flags listed in @code{#:make-flags}.
2450 @item patch-shebangs
2451 Patch shebangs on the installed executable files.
2454 Strip debugging symbols from ELF files (unless @code{#:strip-binaries?}
2455 is false), copying them to the @code{debug} output when available
2456 (@pxref{Installing Debugging Files}).
2459 @vindex %standard-phases
2460 The build-side module @code{(guix build gnu-build-system)} defines
2461 @var{%standard-phases} as the default list of build phases.
2462 @var{%standard-phases} is a list of symbol/procedure pairs, where the
2463 procedure implements the actual phase.
2465 The list of phases used for a particular package can be changed with the
2466 @code{#:phases} parameter. For instance, passing:
2469 #:phases (alist-delete 'configure %standard-phases)
2472 means that all the phases described above will be used, except the
2473 @code{configure} phase.
2475 In addition, this build system ensures that the ``standard'' environment
2476 for GNU packages is available. This includes tools such as GCC, libc,
2477 Coreutils, Bash, Make, Diffutils, grep, and sed (see the @code{(guix
2478 build-system gnu)} module for a complete list.) We call these the
2479 @dfn{implicit inputs} of a package, because package definitions don't
2480 have to mention them.
2483 Other @code{<build-system>} objects are defined to support other
2484 conventions and tools used by free software packages. They inherit most
2485 of @var{gnu-build-system}, and differ mainly in the set of inputs
2486 implicitly added to the build process, and in the list of phases
2487 executed. Some of these build systems are listed below.
2489 @defvr {Scheme Variable} cmake-build-system
2490 This variable is exported by @code{(guix build-system cmake)}. It
2491 implements the build procedure for packages using the
2492 @url{http://www.cmake.org, CMake build tool}.
2494 It automatically adds the @code{cmake} package to the set of inputs.
2495 Which package is used can be specified with the @code{#:cmake}
2498 The @code{#:configure-flags} parameter is taken as a list of flags
2499 passed to the @command{cmake} command. The @code{#:build-type}
2500 parameter specifies in abstract terms the flags passed to the compiler;
2501 it defaults to @code{"RelWithDebInfo"} (short for ``release mode with
2502 debugging information''), which roughly means that code is compiled with
2503 @code{-O2 -g}, as is the case for Autoconf-based packages by default.
2506 @defvr {Scheme Variable} glib-or-gtk-build-system
2507 This variable is exported by @code{(guix build-system glib-or-gtk)}. It
2508 is intended for use with packages making use of GLib or GTK+.
2510 This build system adds the following two phases to the ones defined by
2511 @var{gnu-build-system}:
2514 @item glib-or-gtk-wrap
2515 The phase @code{glib-or-gtk-wrap} ensures that programs found under
2516 @file{bin/} are able to find GLib's ``schemas'' and
2517 @uref{https://developer.gnome.org/gtk3/stable/gtk-running.html, GTK+
2518 modules}. This is achieved by wrapping the programs in launch scripts
2519 that appropriately set the @code{XDG_DATA_DIRS} and @code{GTK_PATH}
2520 environment variables.
2522 It is possible to exclude specific package outputs from that wrapping
2523 process by listing their names in the
2524 @code{#:glib-or-gtk-wrap-excluded-outputs} parameter. This is useful
2525 when an output is known not to contain any GLib or GTK+ binaries, and
2526 where wrapping would gratuitously add a dependency of that output on
2529 @item glib-or-gtk-compile-schemas
2530 The phase @code{glib-or-gtk-compile-schemas} makes sure that all GLib's
2531 @uref{https://developer.gnome.org/gio/stable/glib-compile-schemas.html,
2532 GSettings schemas} are compiled. Compilation is performed by the
2533 @command{glib-compile-schemas} program. It is provided by the package
2534 @code{glib:bin} which is automatically imported by the build system.
2535 The @code{glib} package providing @command{glib-compile-schemas} can be
2536 specified with the @code{#:glib} parameter.
2539 Both phases are executed after the @code{install} phase.
2542 @defvr {Scheme Variable} python-build-system
2543 This variable is exported by @code{(guix build-system python)}. It
2544 implements the more or less standard build procedure used by Python
2545 packages, which consists in running @code{python setup.py build} and
2546 then @code{python setup.py install --prefix=/gnu/store/@dots{}}.
2548 For packages that install stand-alone Python programs under @code{bin/},
2549 it takes care of wrapping these programs so their @code{PYTHONPATH}
2550 environment variable points to all the Python libraries they depend on.
2552 Which Python package is used can be specified with the @code{#:python}
2556 @defvr {Scheme Variable} perl-build-system
2557 This variable is exported by @code{(guix build-system perl)}. It
2558 implements the standard build procedure for Perl packages, which either
2559 consists in running @code{perl Build.PL --prefix=/gnu/store/@dots{}},
2560 followed by @code{Build} and @code{Build install}; or in running
2561 @code{perl Makefile.PL PREFIX=/gnu/store/@dots{}}, followed by
2562 @code{make} and @code{make install}; depending on which of
2563 @code{Build.PL} or @code{Makefile.PL} is present in the package
2564 distribution. Preference is given to the former if both @code{Build.PL}
2565 and @code{Makefile.PL} exist in the package distribution. This
2566 preference can be reversed by specifying @code{#t} for the
2567 @code{#:make-maker?} parameter.
2569 The initial @code{perl Makefile.PL} or @code{perl Build.PL} invocation
2570 passes flags specified by the @code{#:make-maker-flags} or
2571 @code{#:module-build-flags} parameter, respectively.
2573 Which Perl package is used can be specified with @code{#:perl}.
2576 @defvr {Scheme Variable} r-build-system
2577 This variable is exported by @code{(guix build-system r)}. It
2578 implements the build procedure used by @uref{http://r-project.org, R}
2579 packages, which essentially is little more than running @code{R CMD
2580 INSTALL --library=/gnu/store/@dots{}} in an environment where
2581 @code{R_LIBS_SITE} contains the paths to all R package inputs. Tests
2582 are run after installation using the R function
2583 @code{tools::testInstalledPackage}.
2586 @defvr {Scheme Variable} ruby-build-system
2587 This variable is exported by @code{(guix build-system ruby)}. It
2588 implements the RubyGems build procedure used by Ruby packages, which
2589 involves running @code{gem build} followed by @code{gem install}.
2591 The @code{source} field of a package that uses this build system
2592 typically references a gem archive, since this is the format that Ruby
2593 developers use when releasing their software. The build system unpacks
2594 the gem archive, potentially patches the source, runs the test suite,
2595 repackages the gem, and installs it. Additionally, directories and
2596 tarballs may be referenced to allow building unreleased gems from Git or
2597 a traditional source release tarball.
2599 Which Ruby package is used can be specified with the @code{#:ruby}
2600 parameter. A list of additional flags to be passed to the @command{gem}
2601 command can be specified with the @code{#:gem-flags} parameter.
2604 @defvr {Scheme Variable} waf-build-system
2605 This variable is exported by @code{(guix build-system waf)}. It
2606 implements a build procedure around the @code{waf} script. The common
2607 phases---@code{configure}, @code{build}, and @code{install}---are
2608 implemented by passing their names as arguments to the @code{waf}
2611 The @code{waf} script is executed by the Python interpreter. Which
2612 Python package is used to run the script can be specified with the
2613 @code{#:python} parameter.
2616 @defvr {Scheme Variable} haskell-build-system
2617 This variable is exported by @code{(guix build-system haskell)}. It
2618 implements the Cabal build procedure used by Haskell packages, which
2619 involves running @code{runhaskell Setup.hs configure
2620 --prefix=/gnu/store/@dots{}} and @code{runhaskell Setup.hs build}.
2621 Instead of installing the package by running @code{runhaskell Setup.hs
2622 install}, to avoid trying to register libraries in the read-only
2623 compiler store directory, the build system uses @code{runhaskell
2624 Setup.hs copy}, followed by @code{runhaskell Setup.hs register}. In
2625 addition, the build system generates the package documentation by
2626 running @code{runhaskell Setup.hs haddock}, unless @code{#:haddock? #f}
2627 is passed. Optional Haddock parameters can be passed with the help of
2628 the @code{#:haddock-flags} parameter. If the file @code{Setup.hs} is
2629 not found, the build system looks for @code{Setup.lhs} instead.
2631 Which Haskell compiler is used can be specified with the @code{#:haskell}
2632 parameter which defaults to @code{ghc}.
2635 @defvr {Scheme Variable} emacs-build-system
2636 This variable is exported by @code{(guix build-system emacs)}. It
2637 implements an installation procedure similar to the one of Emacs' own
2638 packaging system (@pxref{Packages,,, emacs, The GNU Emacs Manual}).
2640 It first creates the @code{@var{package}-autoloads.el} file, then it
2641 byte compiles all Emacs Lisp files. Differently from the Emacs
2642 packaging system, the Info documentation files are moved to the standard
2643 documentation directory and the @file{dir} file is deleted. Each
2644 package is installed in its own directory under
2645 @file{share/emacs/site-lisp/guix.d}.
2648 Lastly, for packages that do not need anything as sophisticated, a
2649 ``trivial'' build system is provided. It is trivial in the sense that
2650 it provides basically no support: it does not pull any implicit inputs,
2651 and does not have a notion of build phases.
2653 @defvr {Scheme Variable} trivial-build-system
2654 This variable is exported by @code{(guix build-system trivial)}.
2656 This build system requires a @code{#:builder} argument. This argument
2657 must be a Scheme expression that builds the package's output(s)---as
2658 with @code{build-expression->derivation} (@pxref{Derivations,
2659 @code{build-expression->derivation}}).
2668 Conceptually, the @dfn{store} is where derivations that have been
2669 successfully built are stored---by default, under @file{/gnu/store}.
2670 Sub-directories in the store are referred to as @dfn{store paths}. The
2671 store has an associated database that contains information such as the
2672 store paths referred to by each store path, and the list of @emph{valid}
2673 store paths---paths that result from a successful build.
2675 The store is always accessed by the daemon on behalf of its clients
2676 (@pxref{Invoking guix-daemon}). To manipulate the store, clients
2677 connect to the daemon over a Unix-domain socket, send it requests, and
2678 read the result---these are remote procedure calls, or RPCs.
2680 The @code{(guix store)} module provides procedures to connect to the
2681 daemon, and to perform RPCs. These are described below.
2683 @deffn {Scheme Procedure} open-connection [@var{file}] [#:reserve-space? #t]
2684 Connect to the daemon over the Unix-domain socket at @var{file}. When
2685 @var{reserve-space?} is true, instruct it to reserve a little bit of
2686 extra space on the file system so that the garbage collector can still
2687 operate, should the disk become full. Return a server object.
2689 @var{file} defaults to @var{%default-socket-path}, which is the normal
2690 location given the options that were passed to @command{configure}.
2693 @deffn {Scheme Procedure} close-connection @var{server}
2694 Close the connection to @var{server}.
2697 @defvr {Scheme Variable} current-build-output-port
2698 This variable is bound to a SRFI-39 parameter, which refers to the port
2699 where build and error logs sent by the daemon should be written.
2702 Procedures that make RPCs all take a server object as their first
2705 @deffn {Scheme Procedure} valid-path? @var{server} @var{path}
2706 Return @code{#t} when @var{path} is a valid store path.
2709 @deffn {Scheme Procedure} add-text-to-store @var{server} @var{name} @var{text} [@var{references}]
2710 Add @var{text} under file @var{name} in the store, and return its store
2711 path. @var{references} is the list of store paths referred to by the
2712 resulting store path.
2715 @deffn {Scheme Procedure} build-derivations @var{server} @var{derivations}
2716 Build @var{derivations} (a list of @code{<derivation>} objects or
2717 derivation paths), and return when the worker is done building them.
2718 Return @code{#t} on success.
2721 Note that the @code{(guix monads)} module provides a monad as well as
2722 monadic versions of the above procedures, with the goal of making it
2723 more convenient to work with code that accesses the store (@pxref{The
2727 @i{This section is currently incomplete.}
2730 @section Derivations
2733 Low-level build actions and the environment in which they are performed
2734 are represented by @dfn{derivations}. A derivation contain the
2735 following pieces of information:
2739 The outputs of the derivation---derivations produce at least one file or
2740 directory in the store, but may produce more.
2743 The inputs of the derivations, which may be other derivations or plain
2744 files in the store (patches, build scripts, etc.)
2747 The system type targeted by the derivation---e.g., @code{x86_64-linux}.
2750 The file name of a build script in the store, along with the arguments
2754 A list of environment variables to be defined.
2758 @cindex derivation path
2759 Derivations allow clients of the daemon to communicate build actions to
2760 the store. They exist in two forms: as an in-memory representation,
2761 both on the client- and daemon-side, and as files in the store whose
2762 name end in @code{.drv}---these files are referred to as @dfn{derivation
2763 paths}. Derivations paths can be passed to the @code{build-derivations}
2764 procedure to perform the build actions they prescribe (@pxref{The
2767 The @code{(guix derivations)} module provides a representation of
2768 derivations as Scheme objects, along with procedures to create and
2769 otherwise manipulate derivations. The lowest-level primitive to create
2770 a derivation is the @code{derivation} procedure:
2772 @deffn {Scheme Procedure} derivation @var{store} @var{name} @var{builder} @
2773 @var{args} [#:outputs '("out")] [#:hash #f] [#:hash-algo #f] @
2774 [#:recursive? #f] [#:inputs '()] [#:env-vars '()] @
2775 [#:system (%current-system)] [#:references-graphs #f] @
2776 [#:allowed-references #f] [#:leaked-env-vars #f] [#:local-build? #f] @
2777 [#:substitutable? #t]
2778 Build a derivation with the given arguments, and return the resulting
2779 @code{<derivation>} object.
2781 When @var{hash} and @var{hash-algo} are given, a
2782 @dfn{fixed-output derivation} is created---i.e., one whose result is
2783 known in advance, such as a file download. If, in addition,
2784 @var{recursive?} is true, then that fixed output may be an executable
2785 file or a directory and @var{hash} must be the hash of an archive
2786 containing this output.
2788 When @var{references-graphs} is true, it must be a list of file
2789 name/store path pairs. In that case, the reference graph of each store
2790 path is exported in the build environment in the corresponding file, in
2791 a simple text format.
2793 When @var{allowed-references} is true, it must be a list of store items
2794 or outputs that the derivation's output may refer to.
2796 When @var{leaked-env-vars} is true, it must be a list of strings
2797 denoting environment variables that are allowed to ``leak'' from the
2798 daemon's environment to the build environment. This is only applicable
2799 to fixed-output derivations---i.e., when @var{hash} is true. The main
2800 use is to allow variables such as @code{http_proxy} to be passed to
2801 derivations that download files.
2803 When @var{local-build?} is true, declare that the derivation is not a
2804 good candidate for offloading and should rather be built locally
2805 (@pxref{Daemon Offload Setup}). This is the case for small derivations
2806 where the costs of data transfers would outweigh the benefits.
2808 When @var{substitutable?} is false, declare that substitutes of the
2809 derivation's output should not be used (@pxref{Substitutes}). This is
2810 useful, for instance, when building packages that capture details of the
2811 host CPU instruction set.
2815 Here's an example with a shell script as its builder, assuming
2816 @var{store} is an open connection to the daemon, and @var{bash} points
2817 to a Bash executable in the store:
2820 (use-modules (guix utils)
2824 (let ((builder ; add the Bash script to the store
2825 (add-text-to-store store "my-builder.sh"
2826 "echo hello world > $out\n" '())))
2827 (derivation store "foo"
2828 bash `("-e" ,builder)
2829 #:inputs `((,bash) (,builder))
2830 #:env-vars '(("HOME" . "/homeless"))))
2831 @result{} #<derivation /gnu/store/@dots{}-foo.drv => /gnu/store/@dots{}-foo>
2834 As can be guessed, this primitive is cumbersome to use directly. A
2835 better approach is to write build scripts in Scheme, of course! The
2836 best course of action for that is to write the build code as a
2837 ``G-expression'', and to pass it to @code{gexp->derivation}. For more
2838 information, @pxref{G-Expressions}.
2840 Once upon a time, @code{gexp->derivation} did not exist and constructing
2841 derivations with build code written in Scheme was achieved with
2842 @code{build-expression->derivation}, documented below. This procedure
2843 is now deprecated in favor of the much nicer @code{gexp->derivation}.
2845 @deffn {Scheme Procedure} build-expression->derivation @var{store} @
2846 @var{name} @var{exp} @
2847 [#:system (%current-system)] [#:inputs '()] @
2848 [#:outputs '("out")] [#:hash #f] [#:hash-algo #f] @
2849 [#:recursive? #f] [#:env-vars '()] [#:modules '()] @
2850 [#:references-graphs #f] [#:allowed-references #f] @
2851 [#:local-build? #f] [#:substitutable? #t] [#:guile-for-build #f]
2852 Return a derivation that executes Scheme expression @var{exp} as a
2853 builder for derivation @var{name}. @var{inputs} must be a list of
2854 @code{(name drv-path sub-drv)} tuples; when @var{sub-drv} is omitted,
2855 @code{"out"} is assumed. @var{modules} is a list of names of Guile
2856 modules from the current search path to be copied in the store,
2857 compiled, and made available in the load path during the execution of
2858 @var{exp}---e.g., @code{((guix build utils) (guix build
2859 gnu-build-system))}.
2861 @var{exp} is evaluated in an environment where @code{%outputs} is bound
2862 to a list of output/path pairs, and where @code{%build-inputs} is bound
2863 to a list of string/output-path pairs made from @var{inputs}.
2864 Optionally, @var{env-vars} is a list of string pairs specifying the name
2865 and value of environment variables visible to the builder. The builder
2866 terminates by passing the result of @var{exp} to @code{exit}; thus, when
2867 @var{exp} returns @code{#f}, the build is considered to have failed.
2869 @var{exp} is built using @var{guile-for-build} (a derivation). When
2870 @var{guile-for-build} is omitted or is @code{#f}, the value of the
2871 @code{%guile-for-build} fluid is used instead.
2873 See the @code{derivation} procedure for the meaning of
2874 @var{references-graphs}, @var{allowed-references}, @var{local-build?},
2875 and @var{substitutable?}.
2879 Here's an example of a single-output derivation that creates a directory
2880 containing one file:
2883 (let ((builder '(let ((out (assoc-ref %outputs "out")))
2884 (mkdir out) ; create /gnu/store/@dots{}-goo
2885 (call-with-output-file (string-append out "/test")
2887 (display '(hello guix) p))))))
2888 (build-expression->derivation store "goo" builder))
2890 @result{} #<derivation /gnu/store/@dots{}-goo.drv => @dots{}>
2894 @node The Store Monad
2895 @section The Store Monad
2899 The procedures that operate on the store described in the previous
2900 sections all take an open connection to the build daemon as their first
2901 argument. Although the underlying model is functional, they either have
2902 side effects or depend on the current state of the store.
2904 The former is inconvenient: the connection to the build daemon has to be
2905 carried around in all those functions, making it impossible to compose
2906 functions that do not take that parameter with functions that do. The
2907 latter can be problematic: since store operations have side effects
2908 and/or depend on external state, they have to be properly sequenced.
2910 @cindex monadic values
2911 @cindex monadic functions
2912 This is where the @code{(guix monads)} module comes in. This module
2913 provides a framework for working with @dfn{monads}, and a particularly
2914 useful monad for our uses, the @dfn{store monad}. Monads are a
2915 construct that allows two things: associating ``context'' with values
2916 (in our case, the context is the store), and building sequences of
2917 computations (here computations include accesses to the store.) Values
2918 in a monad---values that carry this additional context---are called
2919 @dfn{monadic values}; procedures that return such values are called
2920 @dfn{monadic procedures}.
2922 Consider this ``normal'' procedure:
2925 (define (sh-symlink store)
2926 ;; Return a derivation that symlinks the 'bash' executable.
2927 (let* ((drv (package-derivation store bash))
2928 (out (derivation->output-path drv))
2929 (sh (string-append out "/bin/bash")))
2930 (build-expression->derivation store "sh"
2931 `(symlink ,sh %output))))
2934 Using @code{(guix monads)} and @code{(guix gexp)}, it may be rewritten
2935 as a monadic function:
2938 (define (sh-symlink)
2939 ;; Same, but return a monadic value.
2940 (mlet %store-monad ((drv (package->derivation bash)))
2941 (gexp->derivation "sh"
2942 #~(symlink (string-append #$drv "/bin/bash")
2946 There several things to note in the second version: the @code{store}
2947 parameter is now implicit and is ``threaded'' in the calls to the
2948 @code{package->derivation} and @code{gexp->derivation} monadic
2949 procedures, and the monadic value returned by @code{package->derivation}
2950 is @dfn{bound} using @code{mlet} instead of plain @code{let}.
2952 As it turns out, the call to @code{package->derivation} can even be
2953 omitted since it will take place implicitly, as we will see later
2954 (@pxref{G-Expressions}):
2957 (define (sh-symlink)
2958 (gexp->derivation "sh"
2959 #~(symlink (string-append #$bash "/bin/bash")
2964 @c <https://syntaxexclamation.wordpress.com/2014/06/26/escaping-continuations/>
2965 @c for the funny quote.
2966 Calling the monadic @code{sh-symlink} has no effect. As someone once
2967 said, ``you exit a monad like you exit a building on fire: by running''.
2968 So, to exit the monad and get the desired effect, one must use
2969 @code{run-with-store}:
2972 (run-with-store (open-connection) (sh-symlink))
2973 @result{} /gnu/store/...-sh-symlink
2976 Note that the @code{(guix monad-repl)} module extends Guile's REPL with
2977 new ``meta-commands'' to make it easier to deal with monadic procedures:
2978 @code{run-in-store}, and @code{enter-store-monad}. The former, is used
2979 to ``run'' a single monadic value through the store:
2982 scheme@@(guile-user)> ,run-in-store (package->derivation hello)
2983 $1 = #<derivation /gnu/store/@dots{}-hello-2.9.drv => @dots{}>
2986 The latter enters a recursive REPL, where all the return values are
2987 automatically run through the store:
2990 scheme@@(guile-user)> ,enter-store-monad
2991 store-monad@@(guile-user) [1]> (package->derivation hello)
2992 $2 = #<derivation /gnu/store/@dots{}-hello-2.9.drv => @dots{}>
2993 store-monad@@(guile-user) [1]> (text-file "foo" "Hello!")
2994 $3 = "/gnu/store/@dots{}-foo"
2995 store-monad@@(guile-user) [1]> ,q
2996 scheme@@(guile-user)>
3000 Note that non-monadic values cannot be returned in the
3001 @code{store-monad} REPL.
3003 The main syntactic forms to deal with monads in general are provided by
3004 the @code{(guix monads)} module and are described below.
3006 @deffn {Scheme Syntax} with-monad @var{monad} @var{body} ...
3007 Evaluate any @code{>>=} or @code{return} forms in @var{body} as being
3011 @deffn {Scheme Syntax} return @var{val}
3012 Return a monadic value that encapsulates @var{val}.
3015 @deffn {Scheme Syntax} >>= @var{mval} @var{mproc} ...
3016 @dfn{Bind} monadic value @var{mval}, passing its ``contents'' to monadic
3017 procedures @var{mproc}@dots{}@footnote{This operation is commonly
3018 referred to as ``bind'', but that name denotes an unrelated procedure in
3019 Guile. Thus we use this somewhat cryptic symbol inherited from the
3020 Haskell language.}. There can be one @var{mproc} or several of them, as
3025 (with-monad %state-monad
3027 (lambda (x) (return (+ 1 x)))
3028 (lambda (x) (return (* 2 x)))))
3032 @result{} some-state
3036 @deffn {Scheme Syntax} mlet @var{monad} ((@var{var} @var{mval}) ...) @
3038 @deffnx {Scheme Syntax} mlet* @var{monad} ((@var{var} @var{mval}) ...) @
3040 Bind the variables @var{var} to the monadic values @var{mval} in
3041 @var{body}. The form (@var{var} -> @var{val}) binds @var{var} to the
3042 ``normal'' value @var{val}, as per @code{let}.
3044 @code{mlet*} is to @code{mlet} what @code{let*} is to @code{let}
3045 (@pxref{Local Bindings,,, guile, GNU Guile Reference Manual}).
3048 @deffn {Scheme System} mbegin @var{monad} @var{mexp} ...
3049 Bind @var{mexp} and the following monadic expressions in sequence,
3050 returning the result of the last expression.
3052 This is akin to @code{mlet}, except that the return values of the
3053 monadic expressions are ignored. In that sense, it is analogous to
3054 @code{begin}, but applied to monadic expressions.
3058 The @code{(guix monads)} module provides the @dfn{state monad}, which
3059 allows an additional value---the state---to be @emph{threaded} through
3060 monadic procedure calls.
3062 @defvr {Scheme Variable} %state-monad
3063 The state monad. Procedures in the state monad can access and change
3064 the state that is threaded.
3066 Consider the example below. The @code{square} procedure returns a value
3067 in the state monad. It returns the square of its argument, but also
3068 increments the current state value:
3072 (mlet %state-monad ((count (current-state)))
3073 (mbegin %state-monad
3074 (set-current-state (+ 1 count))
3077 (run-with-state (sequence %state-monad (map square (iota 3))) 0)
3082 When ``run'' through @var{%state-monad}, we obtain that additional state
3083 value, which is the number of @code{square} calls.
3086 @deffn {Monadic Procedure} current-state
3087 Return the current state as a monadic value.
3090 @deffn {Monadic Procedure} set-current-state @var{value}
3091 Set the current state to @var{value} and return the previous state as a
3095 @deffn {Monadic Procedure} state-push @var{value}
3096 Push @var{value} to the current state, which is assumed to be a list,
3097 and return the previous state as a monadic value.
3100 @deffn {Monadic Procedure} state-pop
3101 Pop a value from the current state and return it as a monadic value.
3102 The state is assumed to be a list.
3105 @deffn {Scheme Procedure} run-with-state @var{mval} [@var{state}]
3106 Run monadic value @var{mval} starting with @var{state} as the initial
3107 state. Return two values: the resulting value, and the resulting state.
3110 The main interface to the store monad, provided by the @code{(guix
3111 store)} module, is as follows.
3113 @defvr {Scheme Variable} %store-monad
3114 The store monad---an alias for @var{%state-monad}.
3116 Values in the store monad encapsulate accesses to the store. When its
3117 effect is needed, a value of the store monad must be ``evaluated'' by
3118 passing it to the @code{run-with-store} procedure (see below.)
3121 @deffn {Scheme Procedure} run-with-store @var{store} @var{mval} [#:guile-for-build] [#:system (%current-system)]
3122 Run @var{mval}, a monadic value in the store monad, in @var{store}, an
3123 open store connection.
3126 @deffn {Monadic Procedure} text-file @var{name} @var{text} [@var{references}]
3127 Return as a monadic value the absolute file name in the store of the file
3128 containing @var{text}, a string. @var{references} is a list of store items that the
3129 resulting text file refers to; it defaults to the empty list.
3132 @deffn {Monadic Procedure} interned-file @var{file} [@var{name}] @
3134 Return the name of @var{file} once interned in the store. Use
3135 @var{name} as its store name, or the basename of @var{file} if
3136 @var{name} is omitted.
3138 When @var{recursive?} is true, the contents of @var{file} are added
3139 recursively; if @var{file} designates a flat file and @var{recursive?}
3140 is true, its contents are added, and its permission bits are kept.
3142 The example below adds a file to the store, under two different names:
3145 (run-with-store (open-connection)
3146 (mlet %store-monad ((a (interned-file "README"))
3147 (b (interned-file "README" "LEGU-MIN")))
3148 (return (list a b))))
3150 @result{} ("/gnu/store/rwm@dots{}-README" "/gnu/store/44i@dots{}-LEGU-MIN")
3155 The @code{(guix packages)} module exports the following package-related
3158 @deffn {Monadic Procedure} package-file @var{package} [@var{file}] @
3159 [#:system (%current-system)] [#:target #f] @
3160 [#:output "out"] Return as a monadic
3161 value in the absolute file name of @var{file} within the @var{output}
3162 directory of @var{package}. When @var{file} is omitted, return the name
3163 of the @var{output} directory of @var{package}. When @var{target} is
3164 true, use it as a cross-compilation target triplet.
3167 @deffn {Monadic Procedure} package->derivation @var{package} [@var{system}]
3168 @deffnx {Monadic Procedure} package->cross-derivation @var{package} @
3169 @var{target} [@var{system}]
3170 Monadic version of @code{package-derivation} and
3171 @code{package-cross-derivation} (@pxref{Defining Packages}).
3176 @section G-Expressions
3178 @cindex G-expression
3179 @cindex build code quoting
3180 So we have ``derivations'', which represent a sequence of build actions
3181 to be performed to produce an item in the store (@pxref{Derivations}).
3182 Those build actions are performed when asking the daemon to actually
3183 build the derivations; they are run by the daemon in a container
3184 (@pxref{Invoking guix-daemon}).
3186 @cindex strata of code
3187 It should come as no surprise that we like to write those build actions
3188 in Scheme. When we do that, we end up with two @dfn{strata} of Scheme
3189 code@footnote{The term @dfn{stratum} in this context was coined by
3190 Manuel Serrano et al.@: in the context of their work on Hop. Oleg
3191 Kiselyov, who has written insightful
3192 @url{http://okmij.org/ftp/meta-programming/#meta-scheme, essays and code
3193 on this topic}, refers to this kind of code generation as
3194 @dfn{staging}.}: the ``host code''---code that defines packages, talks
3195 to the daemon, etc.---and the ``build code''---code that actually
3196 performs build actions, such as making directories, invoking
3197 @command{make}, etc.
3199 To describe a derivation and its build actions, one typically needs to
3200 embed build code inside host code. It boils down to manipulating build
3201 code as data, and Scheme's homoiconicity---code has a direct
3202 representation as data---comes in handy for that. But we need more than
3203 Scheme's normal @code{quasiquote} mechanism to construct build
3206 The @code{(guix gexp)} module implements @dfn{G-expressions}, a form of
3207 S-expressions adapted to build expressions. G-expressions, or
3208 @dfn{gexps}, consist essentially in three syntactic forms: @code{gexp},
3209 @code{ungexp}, and @code{ungexp-splicing} (or simply: @code{#~},
3210 @code{#$}, and @code{#$@@}), which are comparable respectively to
3211 @code{quasiquote}, @code{unquote}, and @code{unquote-splicing}
3212 (@pxref{Expression Syntax, @code{quasiquote},, guile, GNU Guile
3213 Reference Manual}). However, there are major differences:
3217 Gexps are meant to be written to a file and run or manipulated by other
3221 When a high-level object such as a package or derivation is unquoted
3222 inside a gexp, the result is as if its output file name had been
3226 Gexps carry information about the packages or derivations they refer to,
3227 and these dependencies are automatically added as inputs to the build
3228 processes that use them.
3231 @cindex lowering, of high-level objects in gexps
3232 This mechanism is not limited to package and derivation
3233 objects: @dfn{compilers} able to ``lower'' other high-level objects to
3234 derivations or files in the store can be defined,
3235 such that these objects can also be inserted
3236 into gexps. For example, a useful type of high-level object that can be
3237 inserted in a gexp is ``file-like objects'', which make it easy to
3238 add files to the store and refer to them in
3239 derivations and such (see @code{local-file} and @code{plain-file}
3242 To illustrate the idea, here is an example of a gexp:
3249 (symlink (string-append #$coreutils "/bin/ls")
3253 This gexp can be passed to @code{gexp->derivation}; we obtain a
3254 derivation that builds a directory containing exactly one symlink to
3255 @file{/gnu/store/@dots{}-coreutils-8.22/bin/ls}:
3258 (gexp->derivation "the-thing" build-exp)
3261 As one would expect, the @code{"/gnu/store/@dots{}-coreutils-8.22"} string is
3262 substituted to the reference to the @var{coreutils} package in the
3263 actual build code, and @var{coreutils} is automatically made an input to
3264 the derivation. Likewise, @code{#$output} (equivalent to @code{(ungexp
3265 output)}) is replaced by a string containing the derivation's output
3268 @cindex cross compilation
3269 In a cross-compilation context, it is useful to distinguish between
3270 references to the @emph{native} build of a package---that can run on the
3271 host---versus references to cross builds of a package. To that end, the
3272 @code{#+} plays the same role as @code{#$}, but is a reference to a
3273 native package build:
3276 (gexp->derivation "vi"
3279 (system* (string-append #+coreutils "/bin/ln")
3281 (string-append #$emacs "/bin/emacs")
3282 (string-append #$output "/bin/vi")))
3283 #:target "mips64el-linux")
3287 In the example above, the native build of @var{coreutils} is used, so
3288 that @command{ln} can actually run on the host; but then the
3289 cross-compiled build of @var{emacs} is referenced.
3291 The syntactic form to construct gexps is summarized below.
3293 @deffn {Scheme Syntax} #~@var{exp}
3294 @deffnx {Scheme Syntax} (gexp @var{exp})
3295 Return a G-expression containing @var{exp}. @var{exp} may contain one
3296 or more of the following forms:
3300 @itemx (ungexp @var{obj})
3301 Introduce a reference to @var{obj}. @var{obj} may have one of the
3302 supported types, for example a package or a
3303 derivation, in which case the @code{ungexp} form is replaced by its
3304 output file name---e.g., @code{"/gnu/store/@dots{}-coreutils-8.22}.
3306 If @var{obj} is a list, it is traversed and references to supported
3307 objects are substituted similarly.
3309 If @var{obj} is another gexp, its contents are inserted and its
3310 dependencies are added to those of the containing gexp.
3312 If @var{obj} is another kind of object, it is inserted as is.
3314 @item #$@var{obj}:@var{output}
3315 @itemx (ungexp @var{obj} @var{output})
3316 This is like the form above, but referring explicitly to the
3317 @var{output} of @var{obj}---this is useful when @var{obj} produces
3318 multiple outputs (@pxref{Packages with Multiple Outputs}).
3321 @itemx #+@var{obj}:output
3322 @itemx (ungexp-native @var{obj})
3323 @itemx (ungexp-native @var{obj} @var{output})
3324 Same as @code{ungexp}, but produces a reference to the @emph{native}
3325 build of @var{obj} when used in a cross compilation context.
3327 @item #$output[:@var{output}]
3328 @itemx (ungexp output [@var{output}])
3329 Insert a reference to derivation output @var{output}, or to the main
3330 output when @var{output} is omitted.
3332 This only makes sense for gexps passed to @code{gexp->derivation}.
3335 @itemx (ungexp-splicing @var{lst})
3336 Like the above, but splices the contents of @var{lst} inside the
3340 @itemx (ungexp-native-splicing @var{lst})
3341 Like the above, but refers to native builds of the objects listed in
3346 G-expressions created by @code{gexp} or @code{#~} are run-time objects
3347 of the @code{gexp?} type (see below.)
3350 @deffn {Scheme Procedure} gexp? @var{obj}
3351 Return @code{#t} if @var{obj} is a G-expression.
3354 G-expressions are meant to be written to disk, either as code building
3355 some derivation, or as plain files in the store. The monadic procedures
3356 below allow you to do that (@pxref{The Store Monad}, for more
3357 information about monads.)
3359 @deffn {Monadic Procedure} gexp->derivation @var{name} @var{exp} @
3360 [#:system (%current-system)] [#:target #f] [#:graft? #t] @
3361 [#:hash #f] [#:hash-algo #f] @
3362 [#:recursive? #f] [#:env-vars '()] [#:modules '()] @
3363 [#:module-path @var{%load-path}] @
3364 [#:references-graphs #f] [#:allowed-references #f] @
3365 [#:leaked-env-vars #f] @
3366 [#:script-name (string-append @var{name} "-builder")] @
3367 [#:local-build? #f] [#:substitutable? #t] [#:guile-for-build #f]
3368 Return a derivation @var{name} that runs @var{exp} (a gexp) with
3369 @var{guile-for-build} (a derivation) on @var{system}; @var{exp} is
3370 stored in a file called @var{script-name}. When @var{target} is true,
3371 it is used as the cross-compilation target triplet for packages referred
3374 Make @var{modules} available in the evaluation context of @var{exp};
3375 @var{modules} is a list of names of Guile modules searched in
3376 @var{module-path} to be copied in the store, compiled, and made available in
3377 the load path during the execution of @var{exp}---e.g., @code{((guix
3378 build utils) (guix build gnu-build-system))}.
3380 @var{graft?} determines whether packages referred to by @var{exp} should be grafted when
3383 When @var{references-graphs} is true, it must be a list of tuples of one of the
3387 (@var{file-name} @var{package})
3388 (@var{file-name} @var{package} @var{output})
3389 (@var{file-name} @var{derivation})
3390 (@var{file-name} @var{derivation} @var{output})
3391 (@var{file-name} @var{store-item})
3394 The right-hand-side of each element of @var{references-graphs} is automatically made
3395 an input of the build process of @var{exp}. In the build environment, each
3396 @var{file-name} contains the reference graph of the corresponding item, in a simple
3399 @var{allowed-references} must be either @code{#f} or a list of output names and packages.
3400 In the latter case, the list denotes store items that the result is allowed to
3401 refer to. Any reference to another store item will lead to a build error.
3403 The other arguments are as for @code{derivation} (@pxref{Derivations}).
3406 @cindex file-like objects
3407 The @code{local-file}, @code{plain-file}, @code{computed-file},
3408 @code{program-file}, and @code{scheme-file} procedures below return
3409 @dfn{file-like objects}. That is, when unquoted in a G-expression,
3410 these objects lead to a file in the store. Consider this G-expression:
3413 #~(system* (string-append #$glibc "/sbin/nscd") "-f"
3414 #$(local-file "/tmp/my-nscd.conf"))
3417 The effect here is to ``intern'' @file{/tmp/my-nscd.conf} by copying it
3418 to the store. Once expanded, for instance @i{via}
3419 @code{gexp->derivation}, the G-expression refers to that copy under
3420 @file{/gnu/store}; thus, modifying or removing the file in @file{/tmp}
3421 does not have any effect on what the G-expression does.
3422 @code{plain-file} can be used similarly; it differs in that the file
3423 content is directly passed as a string.
3425 @deffn {Scheme Procedure} local-file @var{file} [@var{name}] @
3427 Return an object representing local file @var{file} to add to the store; this
3428 object can be used in a gexp. @var{file} will be added to the store under @var{name}--by
3429 default the base name of @var{file}.
3431 When @var{recursive?} is true, the contents of @var{file} are added recursively; if @var{file}
3432 designates a flat file and @var{recursive?} is true, its contents are added, and its
3433 permission bits are kept.
3435 This is the declarative counterpart of the @code{interned-file} monadic
3436 procedure (@pxref{The Store Monad, @code{interned-file}}).
3439 @deffn {Scheme Procedure} plain-file @var{name} @var{content}
3440 Return an object representing a text file called @var{name} with the given
3441 @var{content} (a string) to be added to the store.
3443 This is the declarative counterpart of @code{text-file}.
3446 @deffn {Scheme Procedure} computed-file @var{name} @var{gexp} @
3447 [#:modules '()] [#:options '(#:local-build? #t)]
3448 Return an object representing the store item @var{name}, a file or
3449 directory computed by @var{gexp}. @var{modules} specifies the set of
3450 modules visible in the execution context of @var{gexp}. @var{options}
3451 is a list of additional arguments to pass to @code{gexp->derivation}.
3453 This is the declarative counterpart of @code{gexp->derivation}.
3456 @deffn {Monadic Procedure} gexp->script @var{name} @var{exp}
3457 Return an executable script @var{name} that runs @var{exp} using
3458 @var{guile} with @var{modules} in its search path.
3460 The example below builds a script that simply invokes the @command{ls}
3464 (use-modules (guix gexp) (gnu packages base))
3466 (gexp->script "list-files"
3467 #~(execl (string-append #$coreutils "/bin/ls")
3471 When ``running'' it through the store (@pxref{The Store Monad,
3472 @code{run-with-store}}), we obtain a derivation that produces an
3473 executable file @file{/gnu/store/@dots{}-list-files} along these lines:
3476 #!/gnu/store/@dots{}-guile-2.0.11/bin/guile -ds
3478 (execl (string-append "/gnu/store/@dots{}-coreutils-8.22"/bin/ls")
3483 @deffn {Scheme Procedure} program-file @var{name} @var{exp} @
3484 [#:modules '()] [#:guile #f]
3485 Return an object representing the executable store item @var{name} that
3486 runs @var{gexp}. @var{guile} is the Guile package used to execute that
3487 script, and @var{modules} is the list of modules visible to that script.
3489 This is the declarative counterpart of @code{gexp->script}.
3492 @deffn {Monadic Procedure} gexp->file @var{name} @var{exp}
3493 Return a derivation that builds a file @var{name} containing @var{exp}.
3495 The resulting file holds references to all the dependencies of @var{exp}
3496 or a subset thereof.
3499 @deffn {Scheme Procedure} scheme-file @var{name} @var{exp}
3500 Return an object representing the Scheme file @var{name} that contains
3503 This is the declarative counterpart of @code{gexp->file}.
3506 @deffn {Monadic Procedure} text-file* @var{name} @var{text} @dots{}
3507 Return as a monadic value a derivation that builds a text file
3508 containing all of @var{text}. @var{text} may list, in addition to
3509 strings, objects of any type that can be used in a gexp: packages,
3510 derivations, local file objects, etc. The resulting store file holds
3511 references to all these.
3513 This variant should be preferred over @code{text-file} anytime the file
3514 to create will reference items from the store. This is typically the
3515 case when building a configuration file that embeds store file names,
3519 (define (profile.sh)
3520 ;; Return the name of a shell script in the store that
3521 ;; initializes the 'PATH' environment variable.
3522 (text-file* "profile.sh"
3523 "export PATH=" coreutils "/bin:"
3524 grep "/bin:" sed "/bin\n"))
3527 In this example, the resulting @file{/gnu/store/@dots{}-profile.sh} file
3528 will references @var{coreutils}, @var{grep}, and @var{sed}, thereby
3529 preventing them from being garbage-collected during its lifetime.
3532 @deffn {Scheme Procedure} mixed-text-file @var{name} @var{text} @dots{}
3533 Return an object representing store file @var{name} containing
3534 @var{text}. @var{text} is a sequence of strings and file-like objects,
3538 (mixed-text-file "profile"
3539 "export PATH=" coreutils "/bin:" grep "/bin")
3542 This is the declarative counterpart of @code{text-file*}.
3545 Of course, in addition to gexps embedded in ``host'' code, there are
3546 also modules containing build tools. To make it clear that they are
3547 meant to be used in the build stratum, these modules are kept in the
3548 @code{(guix build @dots{})} name space.
3550 @cindex lowering, of high-level objects in gexps
3551 Internally, high-level objects are @dfn{lowered}, using their compiler,
3552 to either derivations or store items. For instance, lowering a package
3553 yields a derivation, and lowering a @code{plain-file} yields a store
3554 item. This is achieved using the @code{lower-object} monadic procedure.
3556 @deffn {Monadic Procedure} lower-object @var{obj} [@var{system}] @
3558 Return as a value in @var{%store-monad} the derivation or store item
3559 corresponding to @var{obj} for @var{system}, cross-compiling for
3560 @var{target} if @var{target} is true. @var{obj} must be an object that
3561 has an associated gexp compiler, such as a @code{<package>}.
3565 @c *********************************************************************
3569 This section describes tools primarily targeted at developers and users
3570 who write new package definitions. They complement the Scheme
3571 programming interface of Guix in a convenient way.
3574 * Invoking guix build:: Building packages from the command line.
3575 * Invoking guix edit:: Editing package definitions.
3576 * Invoking guix download:: Downloading a file and printing its hash.
3577 * Invoking guix hash:: Computing the cryptographic hash of a file.
3578 * Invoking guix import:: Importing package definitions.
3579 * Invoking guix refresh:: Updating package definitions.
3580 * Invoking guix lint:: Finding errors in package definitions.
3581 * Invoking guix size:: Profiling disk usage.
3582 * Invoking guix graph:: Visualizing the graph of packages.
3583 * Invoking guix environment:: Setting up development environments.
3584 * Invoking guix publish:: Sharing substitutes.
3585 * Invoking guix challenge:: Challenging substitute servers.
3588 @node Invoking guix build
3589 @section Invoking @command{guix build}
3591 The @command{guix build} command builds packages or derivations and
3592 their dependencies, and prints the resulting store paths. Note that it
3593 does not modify the user's profile---this is the job of the
3594 @command{guix package} command (@pxref{Invoking guix package}). Thus,
3595 it is mainly useful for distribution developers.
3597 The general syntax is:
3600 guix build @var{options} @var{package-or-derivation}@dots{}
3603 @var{package-or-derivation} may be either the name of a package found in
3604 the software distribution such as @code{coreutils} or
3605 @code{coreutils-8.20}, or a derivation such as
3606 @file{/gnu/store/@dots{}-coreutils-8.19.drv}. In the former case, a
3607 package with the corresponding name (and optionally version) is searched
3608 for among the GNU distribution modules (@pxref{Package Modules}).
3610 Alternatively, the @code{--expression} option may be used to specify a
3611 Scheme expression that evaluates to a package; this is useful when
3612 disambiguation among several same-named packages or package variants is
3615 The @var{options} may be zero or more of the following:
3619 @item --file=@var{file}
3620 @itemx -f @var{file}
3622 Build the package or derivation that the code within @var{file}
3625 As an example, @var{file} might contain a package definition like this
3626 (@pxref{Defining Packages}):
3629 @verbatiminclude package-hello.scm
3632 @item --expression=@var{expr}
3633 @itemx -e @var{expr}
3634 Build the package or derivation @var{expr} evaluates to.
3636 For example, @var{expr} may be @code{(@@ (gnu packages guile)
3637 guile-1.8)}, which unambiguously designates this specific variant of
3638 version 1.8 of Guile.
3640 Alternately, @var{expr} may be a G-expression, in which case it is used
3641 as a build program passed to @code{gexp->derivation}
3642 (@pxref{G-Expressions}).
3644 Lastly, @var{expr} may refer to a zero-argument monadic procedure
3645 (@pxref{The Store Monad}). The procedure must return a derivation as a
3646 monadic value, which is then passed through @code{run-with-store}.
3650 Build the packages' source derivations, rather than the packages
3653 For instance, @code{guix build -S gcc} returns something like
3654 @file{/gnu/store/@dots{}-gcc-4.7.2.tar.bz2}, which is GCC's source tarball.
3656 The returned source tarball is the result of applying any patches and
3657 code snippets specified in the package's @code{origin} (@pxref{Defining
3661 Fetch and return the source of @var{package-or-derivation} and all their
3662 dependencies, recursively. This is a handy way to obtain a local copy
3663 of all the source code needed to build @var{packages}, allowing you to
3664 eventually build them even without network access. It is an extension
3665 of the @code{--source} option and can accept one of the following
3666 optional argument values:
3670 This value causes the @code{--sources} option to behave in the same way
3671 as the @code{--source} option.
3674 Build all packages' source derivations, including any source that might
3675 be listed as @code{inputs}. This is the default value.
3678 $ guix build --sources tzdata
3679 The following derivations will be built:
3680 /gnu/store/@dots{}-tzdata2015b.tar.gz.drv
3681 /gnu/store/@dots{}-tzcode2015b.tar.gz.drv
3685 Build all packages' source derivations, as well as all source
3686 derivations for packages' transitive inputs. This can be used e.g. to
3687 prefetch package source for later offline building.
3690 $ guix build --sources=transitive tzdata
3691 The following derivations will be built:
3692 /gnu/store/@dots{}-tzcode2015b.tar.gz.drv
3693 /gnu/store/@dots{}-findutils-4.4.2.tar.xz.drv
3694 /gnu/store/@dots{}-grep-2.21.tar.xz.drv
3695 /gnu/store/@dots{}-coreutils-8.23.tar.xz.drv
3696 /gnu/store/@dots{}-make-4.1.tar.xz.drv
3697 /gnu/store/@dots{}-bash-4.3.tar.xz.drv
3703 @item --system=@var{system}
3704 @itemx -s @var{system}
3705 Attempt to build for @var{system}---e.g., @code{i686-linux}---instead of
3706 the host's system type.
3708 An example use of this is on Linux-based systems, which can emulate
3709 different personalities. For instance, passing
3710 @code{--system=i686-linux} on an @code{x86_64-linux} system allows users
3711 to build packages in a complete 32-bit environment.
3713 @item --target=@var{triplet}
3714 @cindex cross-compilation
3715 Cross-build for @var{triplet}, which must be a valid GNU triplet, such
3716 as @code{"mips64el-linux-gnu"} (@pxref{Configuration Names, GNU
3717 configuration triplets,, configure, GNU Configure and Build System}).
3719 @item --with-source=@var{source}
3720 Use @var{source} as the source of the corresponding package.
3721 @var{source} must be a file name or a URL, as for @command{guix
3722 download} (@pxref{Invoking guix download}).
3724 The ``corresponding package'' is taken to be one specified on the
3725 command line whose name matches the base of @var{source}---e.g., if
3726 @var{source} is @code{/src/guile-2.0.10.tar.gz}, the corresponding
3727 package is @code{guile}. Likewise, the version string is inferred from
3728 @var{source}; in the previous example, it's @code{2.0.10}.
3730 This option allows users to try out versions of packages other than the
3731 one provided by the distribution. The example below downloads
3732 @file{ed-1.7.tar.gz} from a GNU mirror and uses that as the source for
3733 the @code{ed} package:
3736 guix build ed --with-source=mirror://gnu/ed/ed-1.7.tar.gz
3739 As a developer, @code{--with-source} makes it easy to test release
3743 guix build guile --with-source=../guile-2.0.9.219-e1bb7.tar.xz
3746 @dots{} or to build from a checkout in a pristine environment:
3749 $ git clone git://git.sv.gnu.org/guix.git
3750 $ guix build guix --with-source=./guix
3754 Do not ``graft'' packages. In practice, this means that package updates
3755 available as grafts are not applied. @xref{Security Updates}, for more
3756 information on grafts.
3760 Return the derivation paths, not the output paths, of the given
3763 @item --root=@var{file}
3764 @itemx -r @var{file}
3765 Make @var{file} a symlink to the result, and register it as a garbage
3769 Return the build log file names or URLs for the given
3770 @var{package-or-derivation}s, or raise an error if build logs are
3773 This works regardless of how packages or derivations are specified. For
3774 instance, the following invocations are equivalent:
3777 guix build --log-file `guix build -d guile`
3778 guix build --log-file `guix build guile`
3779 guix build --log-file guile
3780 guix build --log-file -e '(@@ (gnu packages guile) guile-2.0)'
3783 If a log is unavailable locally, and unless @code{--no-substitutes} is
3784 passed, the command looks for a corresponding log on one of the
3785 substitute servers (as specified with @code{--substitute-urls}.)
3787 So for instance, let's say you want to see the build log of GDB on MIPS
3788 but you're actually on an @code{x86_64} machine:
3791 $ guix build --log-file gdb -s mips64el-linux
3792 http://hydra.gnu.org/log/@dots{}-gdb-7.10
3795 You can freely access a huge library of build logs!
3798 @cindex common build options
3799 In addition, a number of options that control the build process are
3800 common to @command{guix build} and other commands that can spawn builds,
3801 such as @command{guix package} or @command{guix archive}. These are the
3806 @item --load-path=@var{directory}
3807 @itemx -L @var{directory}
3808 Add @var{directory} to the front of the package module search path
3809 (@pxref{Package Modules}).
3811 This allows users to define their own packages and make them visible to
3812 the command-line tools.
3816 Keep the build tree of failed builds. Thus, if a build fail, its build
3817 tree is kept under @file{/tmp}, in a directory whose name is shown at
3818 the end of the build log. This is useful when debugging build issues.
3822 Do not build the derivations.
3825 When substituting a pre-built binary fails, fall back to building
3828 @item --substitute-urls=@var{urls}
3829 @anchor{client-substitute-urls}
3830 Consider @var{urls} the whitespace-separated list of substitute source
3831 URLs, overriding the default list of URLs of @command{guix-daemon}
3832 (@pxref{daemon-substitute-urls,, @command{guix-daemon} URLs}).
3834 This means that substitutes may be downloaded from @var{urls}, provided
3835 they are signed by a key authorized by the system administrator
3836 (@pxref{Substitutes}).
3838 @item --no-substitutes
3839 Do not use substitutes for build products. That is, always build things
3840 locally instead of allowing downloads of pre-built binaries
3841 (@pxref{Substitutes}).
3843 @item --no-build-hook
3844 Do not attempt to offload builds @i{via} the daemon's ``build hook''
3845 (@pxref{Daemon Offload Setup}). That is, always build things locally
3846 instead of offloading builds to remote machines.
3848 @item --max-silent-time=@var{seconds}
3849 When the build or substitution process remains silent for more than
3850 @var{seconds}, terminate it and report a build failure.
3852 @item --timeout=@var{seconds}
3853 Likewise, when the build or substitution process lasts for more than
3854 @var{seconds}, terminate it and report a build failure.
3856 By default there is no timeout. This behavior can be restored with
3859 @item --verbosity=@var{level}
3860 Use the given verbosity level. @var{level} must be an integer between 0
3861 and 5; higher means more verbose output. Setting a level of 4 or more
3862 may be helpful when debugging setup issues with the build daemon.
3864 @item --cores=@var{n}
3866 Allow the use of up to @var{n} CPU cores for the build. The special
3867 value @code{0} means to use as many CPU cores as available.
3869 @item --max-jobs=@var{n}
3871 Allow at most @var{n} build jobs in parallel. @xref{Invoking
3872 guix-daemon, @code{--max-jobs}}, for details about this option and the
3873 equivalent @command{guix-daemon} option.
3877 Behind the scenes, @command{guix build} is essentially an interface to
3878 the @code{package-derivation} procedure of the @code{(guix packages)}
3879 module, and to the @code{build-derivations} procedure of the @code{(guix
3880 derivations)} module.
3882 In addition to options explicitly passed on the command line,
3883 @command{guix build} and other @command{guix} commands that support
3884 building honor the @code{GUIX_BUILD_OPTIONS} environment variable.
3886 @defvr {Environment Variable} GUIX_BUILD_OPTIONS
3887 Users can define this variable to a list of command line options that
3888 will automatically be used by @command{guix build} and other
3889 @command{guix} commands that can perform builds, as in the example
3893 $ export GUIX_BUILD_OPTIONS="--no-substitutes -c 2 -L /foo/bar"
3896 These options are parsed independently, and the result is appended to
3897 the parsed command-line options.
3901 @node Invoking guix edit
3902 @section Invoking @command{guix edit}
3904 @cindex package definition, editing
3905 So many packages, so many source files! The @command{guix edit} command
3906 facilitates the life of packagers by pointing their editor at the source
3907 file containing the definition of the specified packages. For instance:
3910 guix edit gcc-4.8 vim
3914 launches the program specified in the @code{EDITOR} environment variable
3915 to edit the recipe of GCC@tie{}4.8.4 and that of Vim.
3917 If you are using Emacs, note that the Emacs user interface provides
3918 similar functionality in the ``package info'' and ``package list''
3919 buffers created by @kbd{M-x guix-search-by-name} and similar commands
3920 (@pxref{Emacs Commands}).
3923 @node Invoking guix download
3924 @section Invoking @command{guix download}
3926 When writing a package definition, developers typically need to download
3927 the package's source tarball, compute its SHA256 hash, and write that
3928 hash in the package definition (@pxref{Defining Packages}). The
3929 @command{guix download} tool helps with this task: it downloads a file
3930 from the given URI, adds it to the store, and prints both its file name
3931 in the store and its SHA256 hash.
3933 The fact that the downloaded file is added to the store saves bandwidth:
3934 when the developer eventually tries to build the newly defined package
3935 with @command{guix build}, the source tarball will not have to be
3936 downloaded again because it is already in the store. It is also a
3937 convenient way to temporarily stash files, which may be deleted
3938 eventually (@pxref{Invoking guix gc}).
3940 The @command{guix download} command supports the same URIs as used in
3941 package definitions. In particular, it supports @code{mirror://} URIs.
3942 @code{https} URIs (HTTP over TLS) are supported @emph{provided} the
3943 Guile bindings for GnuTLS are available in the user's environment; when
3944 they are not available, an error is raised. @xref{Guile Preparations,
3945 how to install the GnuTLS bindings for Guile,, gnutls-guile,
3946 GnuTLS-Guile}, for more information.
3948 The following option is available:
3951 @item --format=@var{fmt}
3953 Write the hash in the format specified by @var{fmt}. For more
3954 information on the valid values for @var{fmt}, @pxref{Invoking guix hash}.
3957 @node Invoking guix hash
3958 @section Invoking @command{guix hash}
3960 The @command{guix hash} command computes the SHA256 hash of a file.
3961 It is primarily a convenience tool for anyone contributing to the
3962 distribution: it computes the cryptographic hash of a file, which can be
3963 used in the definition of a package (@pxref{Defining Packages}).
3965 The general syntax is:
3968 guix hash @var{option} @var{file}
3971 @command{guix hash} has the following option:
3975 @item --format=@var{fmt}
3977 Write the hash in the format specified by @var{fmt}.
3979 Supported formats: @code{nix-base32}, @code{base32}, @code{base16}
3980 (@code{hex} and @code{hexadecimal} can be used as well).
3982 If the @option{--format} option is not specified, @command{guix hash}
3983 will output the hash in @code{nix-base32}. This representation is used
3984 in the definitions of packages.
3988 Compute the hash on @var{file} recursively.
3990 In this case, the hash is computed on an archive containing @var{file},
3991 including its children if it is a directory. Some of @var{file}'s
3992 meta-data is part of the archive; for instance, when @var{file} is a
3993 regular file, the hash is different depending on whether @var{file} is
3994 executable or not. Meta-data such as time stamps has no impact on the
3995 hash (@pxref{Invoking guix archive}).
3996 @c FIXME: Replace xref above with xref to an ``Archive'' section when
4001 @node Invoking guix import
4002 @section Invoking @command{guix import}
4004 @cindex importing packages
4005 @cindex package import
4006 @cindex package conversion
4007 The @command{guix import} command is useful for people willing to add a
4008 package to the distribution but who'd rather do as little work as
4009 possible to get there---a legitimate demand. The command knows of a few
4010 repositories from which it can ``import'' package meta-data. The result
4011 is a package definition, or a template thereof, in the format we know
4012 (@pxref{Defining Packages}).
4014 The general syntax is:
4017 guix import @var{importer} @var{options}@dots{}
4020 @var{importer} specifies the source from which to import package
4021 meta-data, and @var{options} specifies a package identifier and other
4022 options specific to @var{importer}. Currently, the available
4027 Import meta-data for the given GNU package. This provides a template
4028 for the latest version of that GNU package, including the hash of its
4029 source tarball, and its canonical synopsis and description.
4031 Additional information such as the package's dependencies and its
4032 license needs to be figured out manually.
4034 For example, the following command returns a package definition for
4038 guix import gnu hello
4041 Specific command-line options are:
4044 @item --key-download=@var{policy}
4045 As for @code{guix refresh}, specify the policy to handle missing OpenPGP
4046 keys when verifying the package's signature. @xref{Invoking guix
4047 refresh, @code{--key-download}}.
4052 Import meta-data from the @uref{https://pypi.python.org/, Python Package
4053 Index}@footnote{This functionality requires Guile-JSON to be installed.
4054 @xref{Requirements}.}. Information is taken from the JSON-formatted
4055 description available at @code{pypi.python.org} and usually includes all
4056 the relevant information, including package dependencies.
4058 The command below imports meta-data for the @code{itsdangerous} Python
4062 guix import pypi itsdangerous
4067 Import meta-data from @uref{https://rubygems.org/,
4068 RubyGems}@footnote{This functionality requires Guile-JSON to be
4069 installed. @xref{Requirements}.}. Information is taken from the
4070 JSON-formatted description available at @code{rubygems.org} and includes
4071 most relevant information, including runtime dependencies. There are
4072 some caveats, however. The meta-data doesn't distinguish between
4073 synopses and descriptions, so the same string is used for both fields.
4074 Additionally, the details of non-Ruby dependencies required to build
4075 native extensions is unavailable and left as an exercise to the
4078 The command below imports meta-data for the @code{rails} Ruby package:
4081 guix import gem rails
4086 Import meta-data from @uref{https://www.metacpan.org/, MetaCPAN}.
4087 Information is taken from the JSON-formatted meta-data provided through
4088 @uref{https://api.metacpan.org/, MetaCPAN's API} and includes most
4089 relevant information, such as module dependencies. License information
4090 should be checked closely. If Perl is available in the store, then the
4091 @code{corelist} utility will be used to filter core modules out of the
4092 list of dependencies.
4094 The command command below imports meta-data for the @code{Acme::Boolean}
4098 guix import cpan Acme::Boolean
4103 Import meta-data from @uref{http://cran.r-project.org/, CRAN}, the
4104 central repository for the @uref{http://r-project.org, GNU@tie{}R
4105 statistical and graphical environment}.
4107 Information is extracted from the HTML package description.
4109 The command command below imports meta-data for the @code{Cairo}
4113 guix import cran Cairo
4117 Import meta-data from a local copy of the source of the
4118 @uref{http://nixos.org/nixpkgs/, Nixpkgs distribution}@footnote{This
4119 relies on the @command{nix-instantiate} command of
4120 @uref{http://nixos.org/nix/, Nix}.}. Package definitions in Nixpkgs are
4121 typically written in a mixture of Nix-language and Bash code. This
4122 command only imports the high-level package structure that is written in
4123 the Nix language. It normally includes all the basic fields of a
4126 When importing a GNU package, the synopsis and descriptions are replaced
4127 by their canonical upstream variant.
4129 As an example, the command below imports the package definition of
4130 LibreOffice (more precisely, it imports the definition of the package
4131 bound to the @code{libreoffice} top-level attribute):
4134 guix import nix ~/path/to/nixpkgs libreoffice
4139 Import meta-data from Haskell community's central package archive
4140 @uref{https://hackage.haskell.org/, Hackage}. Information is taken from
4141 Cabal files and includes all the relevant information, including package
4144 Specific command-line options are:
4149 Read a Cabal file from the standard input.
4150 @item --no-test-dependencies
4152 Do not include dependencies required by the test suites only.
4153 @item --cabal-environment=@var{alist}
4154 @itemx -e @var{alist}
4155 @var{alist} is a Scheme alist defining the environment in which the
4156 Cabal conditionals are evaluated. The accepted keys are: @code{os},
4157 @code{arch}, @code{impl} and a string representing the name of a flag.
4158 The value associated with a flag has to be either the symbol
4159 @code{true} or @code{false}. The value associated with other keys
4160 has to conform to the Cabal file format definition. The default value
4161 associated with the keys @code{os}, @code{arch} and @code{impl} is
4162 @samp{linux}, @samp{x86_64} and @samp{ghc} respectively.
4165 The command below imports meta-data for the latest version of the
4166 @code{HTTP} Haskell package without including test dependencies and
4167 specifying the value of the flag @samp{network-uri} as @code{false}:
4170 guix import hackage -t -e "'((\"network-uri\" . false))" HTTP
4173 A specific package version may optionally be specified by following the
4174 package name by a hyphen and a version number as in the following example:
4177 guix import hackage mtl-2.1.3.1
4182 Import meta-data from an Emacs Lisp Package Archive (ELPA) package
4183 repository (@pxref{Packages,,, emacs, The GNU Emacs Manual}).
4185 Specific command-line options are:
4188 @item --archive=@var{repo}
4189 @itemx -a @var{repo}
4190 @var{repo} identifies the archive repository from which to retrieve the
4191 information. Currently the supported repositories and their identifiers
4195 @uref{http://elpa.gnu.org/packages, GNU}, selected by the @code{gnu}
4196 identifier. This is the default.
4199 @uref{http://stable.melpa.org/packages, MELPA-Stable}, selected by the
4200 @code{melpa-stable} identifier.
4203 @uref{http://melpa.org/packages, MELPA}, selected by the @code{melpa}
4209 The structure of the @command{guix import} code is modular. It would be
4210 useful to have more importers for other package formats, and your help
4211 is welcome here (@pxref{Contributing}).
4213 @node Invoking guix refresh
4214 @section Invoking @command{guix refresh}
4216 The primary audience of the @command{guix refresh} command is developers
4217 of the GNU software distribution. By default, it reports any packages
4218 provided by the distribution that are outdated compared to the latest
4219 upstream version, like this:
4223 gnu/packages/gettext.scm:29:13: gettext would be upgraded from 0.18.1.1 to 0.18.2.1
4224 gnu/packages/glib.scm:77:12: glib would be upgraded from 2.34.3 to 2.37.0
4227 It does so by browsing each package's FTP directory and determining the
4228 highest version number of the source tarballs therein. The command
4229 knows how to update specific types of packages: GNU packages, ELPA
4230 packages, etc.---see the documentation for @option{--type} below. The
4231 are many packages, though, for which it lacks a method to determine
4232 whether a new upstream release is available. However, the mechanism is
4233 extensible, so feel free to get in touch with us to add a new method!
4235 When passed @code{--update}, it modifies distribution source files to
4236 update the version numbers and source tarball hashes of those packages'
4237 recipes (@pxref{Defining Packages}). This is achieved by downloading
4238 each package's latest source tarball and its associated OpenPGP
4239 signature, authenticating the downloaded tarball against its signature
4240 using @command{gpg}, and finally computing its hash. When the public
4241 key used to sign the tarball is missing from the user's keyring, an
4242 attempt is made to automatically retrieve it from a public key server;
4243 when it's successful, the key is added to the user's keyring; otherwise,
4244 @command{guix refresh} reports an error.
4246 The following options are supported:
4252 Update distribution source files (package recipes) in place. This is
4253 usually run from a checkout of the Guix source tree (@pxref{Running
4254 Guix Before It Is Installed}):
4257 $ ./pre-inst-env guix refresh -s non-core
4260 @xref{Defining Packages}, for more information on package definitions.
4262 @item --select=[@var{subset}]
4263 @itemx -s @var{subset}
4264 Select all the packages in @var{subset}, one of @code{core} or
4267 The @code{core} subset refers to all the packages at the core of the
4268 distribution---i.e., packages that are used to build ``everything
4269 else''. This includes GCC, libc, Binutils, Bash, etc. Usually,
4270 changing one of these packages in the distribution entails a rebuild of
4271 all the others. Thus, such updates are an inconvenience to users in
4272 terms of build time or bandwidth used to achieve the upgrade.
4274 The @code{non-core} subset refers to the remaining packages. It is
4275 typically useful in cases where an update of the core packages would be
4278 @item --type=@var{updater}
4279 @itemx -t @var{updater}
4280 Select only packages handled by @var{updater} (may be a comma-separated
4281 list of updaters). Currently, @var{updater} may be one of:
4285 the updater for GNU packages;
4287 the updater for @uref{http://elpa.gnu.org/, ELPA} packages;
4289 the updater fro @uref{http://cran.r-project.org/, CRAN} packages.
4292 For instance, the following commands only checks for updates of Emacs
4293 packages hosted at @code{elpa.gnu.org} and updates of CRAN packages:
4296 $ guix refresh --type=elpa,cran
4297 gnu/packages/statistics.scm:819:13: r-testthat would be upgraded from 0.10.0 to 0.11.0
4298 gnu/packages/emacs.scm:856:13: emacs-auctex would be upgraded from 11.88.6 to 11.88.9
4303 In addition, @command{guix refresh} can be passed one or more package
4304 names, as in this example:
4307 $ ./pre-inst-env guix refresh -u emacs idutils gcc-4.8.4
4311 The command above specifically updates the @code{emacs} and
4312 @code{idutils} packages. The @code{--select} option would have no
4313 effect in this case.
4315 When considering whether to upgrade a package, it is sometimes
4316 convenient to know which packages would be affected by the upgrade and
4317 should be checked for compatibility. For this the following option may
4318 be used when passing @command{guix refresh} one or more package names:
4322 @item --list-updaters
4324 List available updaters and exit (see @option{--type} above.)
4326 @item --list-dependent
4328 List top-level dependent packages that would need to be rebuilt as a
4329 result of upgrading one or more packages.
4333 Be aware that the @code{--list-dependent} option only
4334 @emph{approximates} the rebuilds that would be required as a result of
4335 an upgrade. More rebuilds might be required under some circumstances.
4338 $ guix refresh --list-dependent flex
4339 Building the following 120 packages would ensure 213 dependent packages are rebuilt:
4340 hop-2.4.0 geiser-0.4 notmuch-0.18 mu-0.9.9.5 cflow-1.4 idutils-4.6 @dots{}
4343 The command above lists a set of packages that could be built to check
4344 for compatibility with an upgraded @code{flex} package.
4346 The following options can be used to customize GnuPG operation:
4350 @item --gpg=@var{command}
4351 Use @var{command} as the GnuPG 2.x command. @var{command} is searched
4352 for in @code{$PATH}.
4354 @item --key-download=@var{policy}
4355 Handle missing OpenPGP keys according to @var{policy}, which may be one
4360 Always download missing OpenPGP keys from the key server, and add them
4361 to the user's GnuPG keyring.
4364 Never try to download missing OpenPGP keys. Instead just bail out.
4367 When a package signed with an unknown OpenPGP key is encountered, ask
4368 the user whether to download it or not. This is the default behavior.
4371 @item --key-server=@var{host}
4372 Use @var{host} as the OpenPGP key server when importing a public key.
4376 @node Invoking guix lint
4377 @section Invoking @command{guix lint}
4378 The @command{guix lint} is meant to help package developers avoid common
4379 errors and use a consistent style. It runs a number of checks on a
4380 given set of packages in order to find common mistakes in their
4381 definitions. Available @dfn{checkers} include (see
4382 @code{--list-checkers} for a complete list):
4387 Validate certain typographical and stylistic rules about package
4388 descriptions and synopses.
4390 @item inputs-should-be-native
4391 Identify inputs that should most likely be native inputs.
4395 @itemx source-file-name
4396 Probe @code{home-page} and @code{source} URLs and report those that are
4397 invalid. Check that the source file name is meaningful, e.g. is not
4398 just a version number or ``git-checkout'', and should not have a
4399 @code{file-name} declared (@pxref{origin Reference}).
4402 Warn about obvious source code formatting issues: trailing white space,
4403 use of tabulations, etc.
4406 The general syntax is:
4409 guix lint @var{options} @var{package}@dots{}
4412 If no package is given on the command line, then all packages are checked.
4413 The @var{options} may be zero or more of the following:
4419 Only enable the checkers specified in a comma-separated list using the
4420 names returned by @code{--list-checkers}.
4422 @item --list-checkers
4424 List and describe all the available checkers that will be run on packages
4429 @node Invoking guix size
4430 @section Invoking @command{guix size}
4432 The @command{guix size} command helps package developers profile the
4433 disk usage of packages. It is easy to overlook the impact of an
4434 additional dependency added to a package, or the impact of using a
4435 single output for a package that could easily be split (@pxref{Packages
4436 with Multiple Outputs}). These are the typical issues that
4437 @command{guix size} can highlight.
4439 The command can be passed a package specification such as @code{gcc-4.8}
4440 or @code{guile:debug}, or a file name in the store. Consider this
4444 $ guix size coreutils
4445 store item total self
4446 /gnu/store/@dots{}-coreutils-8.23 70.0 13.9 19.8%
4447 /gnu/store/@dots{}-gmp-6.0.0a 55.3 2.5 3.6%
4448 /gnu/store/@dots{}-acl-2.2.52 53.7 0.5 0.7%
4449 /gnu/store/@dots{}-attr-2.4.46 53.2 0.3 0.5%
4450 /gnu/store/@dots{}-gcc-4.8.4-lib 52.9 15.7 22.4%
4451 /gnu/store/@dots{}-glibc-2.21 37.2 37.2 53.1%
4455 The store items listed here constitute the @dfn{transitive closure} of
4456 Coreutils---i.e., Coreutils and all its dependencies, recursively---as
4457 would be returned by:
4460 $ guix gc -R /gnu/store/@dots{}-coreutils-8.23
4463 Here the output shows 3 columns next to store items. The first column,
4464 labeled ``total'', shows the size in mebibytes (MiB) of the closure of
4465 the store item---that is, its own size plus the size of all its
4466 dependencies. The next column, labeled ``self'', shows the size of the
4467 item itself. The last column shows the ratio of the item's size to the
4468 space occupied by all the items listed here.
4470 In this example, we see that the closure of Coreutils weighs in at
4471 70@tie{}MiB, half of which is taken by libc. (That libc represents a
4472 large fraction of the closure is not a problem @i{per se} because it is
4473 always available on the system anyway.)
4475 When the package passed to @command{guix size} is available in the
4476 store, @command{guix size} queries the daemon to determine its
4477 dependencies, and measures its size in the store, similar to @command{du
4478 -ms --apparent-size} (@pxref{du invocation,,, coreutils, GNU
4481 When the given package is @emph{not} in the store, @command{guix size}
4482 reports information based on information about the available substitutes
4483 (@pxref{Substitutes}). This allows it to profile disk usage of store
4484 items that are not even on disk, only available remotely.
4486 The available options are:
4490 @item --substitute-urls=@var{urls}
4491 Use substitute information from @var{urls}.
4492 @xref{client-substitute-urls, the same option for @code{guix build}}.
4494 @item --map-file=@var{file}
4495 Write to @var{file} a graphical map of disk usage as a PNG file.
4497 For the example above, the map looks like this:
4499 @image{images/coreutils-size-map,5in,, map of Coreutils disk usage
4500 produced by @command{guix size}}
4502 This option requires that
4503 @uref{http://wingolog.org/software/guile-charting/, Guile-Charting} be
4504 installed and visible in Guile's module search path. When that is not
4505 the case, @command{guix size} fails as it tries to load it.
4507 @item --system=@var{system}
4508 @itemx -s @var{system}
4509 Consider packages for @var{system}---e.g., @code{x86_64-linux}.
4513 @node Invoking guix graph
4514 @section Invoking @command{guix graph}
4517 Packages and their dependencies form a @dfn{graph}, specifically a
4518 directed acyclic graph (DAG). It can quickly become difficult to have a
4519 mental model of the package DAG, so the @command{guix graph} command is
4520 here to provide a visual representation of the DAG. @command{guix
4521 graph} emits a DAG representation in the input format of
4522 @uref{http://www.graphviz.org/, Graphviz}, so its output can be passed
4523 directly to Graphviz's @command{dot} command, for instance. The general
4527 guix graph @var{options} @var{package}@dots{}
4530 For example, the following command generates a PDF file representing the
4531 package DAG for the GNU@tie{}Core Utilities, showing its build-time
4535 guix graph coreutils | dot -Tpdf > dag.pdf
4538 The output looks like this:
4540 @image{images/coreutils-graph,2in,,Dependency graph of the GNU Coreutils}
4542 Nice little graph, no?
4544 But there's more than one graph! The one above is concise: it's the
4545 graph of package objects, omitting implicit inputs such as GCC, libc,
4546 grep, etc. It's often useful to have such a concise graph, but
4547 sometimes you want to see more details. @command{guix graph} supports
4548 several types of graphs, allowing you to choose the level of details:
4552 This is the default type, the one we used above. It shows the DAG of
4553 package objects, excluding implicit dependencies. It is concise, but
4554 filters out many details.
4557 This is the package DAG, @emph{including} implicit inputs.
4559 For instance, the following command:
4562 guix graph --type=bag-emerged coreutils | dot -Tpdf > dag.pdf
4565 ... yields this bigger graph:
4567 @image{images/coreutils-bag-graph,,5in,Detailed dependency graph of the GNU Coreutils}
4569 At the bottom of the graph, we see all the implicit inputs of
4570 @var{gnu-build-system} (@pxref{Build Systems, @code{gnu-build-system}}).
4572 Now, note that the dependencies of those implicit inputs---that is, the
4573 @dfn{bootstrap dependencies} (@pxref{Bootstrapping})---are not shown
4574 here, for conciseness.
4577 Similar to @code{bag-emerged}, but this time including all the bootstrap
4581 This is the most detailed representation: It shows the DAG of
4582 derivations (@pxref{Derivations}) and plain store items. Compared to
4583 the above representation, many additional nodes are visible, including
4584 builds scripts, patches, Guile modules, etc.
4588 All the above types correspond to @emph{build-time dependencies}. The
4589 following graph type represents the @emph{run-time dependencies}:
4593 This is the graph of @dfn{references} of a package output, as returned
4594 by @command{guix gc --references} (@pxref{Invoking guix gc}).
4596 If the given package output is not available in the store, @command{guix
4597 graph} attempts to obtain dependency information from substitutes.
4600 The available options are the following:
4603 @item --type=@var{type}
4604 @itemx -t @var{type}
4605 Produce a graph output of @var{type}, where @var{type} must be one of
4606 the values listed above.
4609 List the supported graph types.
4611 @item --expression=@var{expr}
4612 @itemx -e @var{expr}
4613 Consider the package @var{expr} evaluates to.
4615 This is useful to precisely refer to a package, as in this example:
4618 guix graph -e '(@@@@ (gnu packages commencement) gnu-make-final)'
4623 @node Invoking guix environment
4624 @section Invoking @command{guix environment}
4626 @cindex reproducible build environments
4627 @cindex development environments
4628 The purpose of @command{guix environment} is to assist hackers in
4629 creating reproducible development environments without polluting their
4630 package profile. The @command{guix environment} tool takes one or more
4631 packages, builds all of the necessary inputs, and creates a shell
4632 environment to use them.
4634 The general syntax is:
4637 guix environment @var{options} @var{package}@dots{}
4640 The following example spawns a new shell set up for the development of
4644 guix environment guile
4647 If the specified packages are not built yet, @command{guix environment}
4648 automatically builds them. The new shell's environment is an augmented
4649 version of the environment that @command{guix environment} was run in.
4650 It contains the necessary search paths for building the given package
4651 added to the existing environment variables. To create a ``pure''
4652 environment in which the original environment variables have been unset,
4653 use the @code{--pure} option@footnote{Users sometimes wrongfully augment
4654 environment variables such as @code{PATH} in their @file{~/.bashrc}
4655 file. As a consequence, when @code{guix environment} launches it, Bash
4656 may read @file{~/.bashrc}, thereby introducing ``impurities'' in these
4657 environment variables. It is an error to define such environment
4658 variables in @file{.bashrc}; instead, they should be defined in
4659 @file{.bash_profile}, which is sourced only by log-in shells.
4660 @xref{Bash Startup Files,,, bash, The GNU Bash Reference Manual}, for
4661 details on Bash start-up files.}.
4663 @vindex GUIX_ENVIRONMENT
4664 @command{guix environment} defines the @code{GUIX_ENVIRONMENT}
4665 variable in the shell it spaws. This allows users to, say, define a
4666 specific prompt for development environments in their @file{.bashrc}
4667 (@pxref{Bash Startup Files,,, bash, The GNU Bash Reference Manual}):
4670 if [ -n "$GUIX_ENVIRONMENT" ]
4672 export PS1="\u@@\h \w [dev]\$ "
4676 Additionally, more than one package may be specified, in which case the
4677 union of the inputs for the given packages are used. For example, the
4678 command below spawns a shell where all of the dependencies of both Guile
4679 and Emacs are available:
4682 guix environment guile emacs
4685 Sometimes an interactive shell session is not desired. An arbitrary
4686 command may be invoked by placing the @code{--} token to separate the
4687 command from the rest of the arguments:
4690 guix environment guile -- make -j4
4693 In other situations, it is more convenient to specify the list of
4694 packages needed in the environment. For example, the following command
4695 runs @command{python} from an environment containing Python@tie{}2.7 and
4699 guix environment --ad-hoc python2-numpy python-2.7 -- python
4702 Furthermore, one might want the dependencies of a package and also some
4703 additional packages that are not build-time or runtime dependencies, but
4704 are useful when developing nonetheless. Because of this, the
4705 @code{--ad-hoc} flag is positional. Packages appearing before
4706 @code{--ad-hoc} are interpreted as packages whose dependencies will be
4707 added to the environment. Packages appearing after are interpreted as
4708 packages that will be added to the environment directly. For example,
4709 the following command creates a Guix development environment that
4710 additionally includes Git and strace:
4713 guix environment guix --ad-hoc git strace
4716 Sometimes it is desirable to isolate the environment as much as
4717 possible, for maximal purity and reproducibility. In particular, when
4718 using Guix on a host distro that is not GuixSD, it is desirable to
4719 prevent access to @file{/usr/bin} and other system-wide resources from
4720 the development environment. For example, the following command spawns
4721 a Guile REPL in a ``container'' where only the store and the current
4722 working directory are mounted:
4725 guix environment --ad-hoc --container guile -- guile
4728 The available options are summarized below.
4731 @item --expression=@var{expr}
4732 @itemx -e @var{expr}
4733 Create an environment for the package or list of packages that
4734 @var{expr} evaluates to.
4736 For example, running:
4739 guix environment -e '(@@ (gnu packages maths) petsc-openmpi)'
4742 starts a shell with the environment for this specific variant of the
4748 guix environment --ad-hoc -e '(@ (gnu) %base-packages)'
4751 starts a shell with all the GuixSD base packages available.
4753 @item --load=@var{file}
4754 @itemx -l @var{file}
4755 Create an environment for the package or list of packages that the code
4756 within @var{file} evaluates to.
4758 As an example, @var{file} might contain a definition like this
4759 (@pxref{Defining Packages}):
4762 @verbatiminclude environment-gdb.scm
4766 Include all specified packages in the resulting environment, as if an
4767 @i{ad hoc} package were defined with them as inputs. This option is
4768 useful for quickly creating an environment without having to write a
4769 package expression to contain the desired inputs.
4771 For instance, the command:
4774 guix environment --ad-hoc guile guile-sdl -- guile
4777 runs @command{guile} in an environment where Guile and Guile-SDL are
4780 Note that this example implicitly asks for the default output of
4781 @code{guile} and @code{guile-sdl} but it is possible to ask for a
4782 specific output---e.g., @code{glib:bin} asks for the @code{bin} output
4783 of @code{glib} (@pxref{Packages with Multiple Outputs}).
4785 This option may be composed with the default behavior of @command{guix
4786 environment}. Packages appearing before @code{--ad-hoc} are interpreted
4787 as packages whose dependencies will be added to the environment, the
4788 default behavior. Packages appearing after are interpreted as packages
4789 that will be added to the environment directly.
4792 Unset existing environment variables when building the new environment.
4793 This has the effect of creating an environment in which search paths
4794 only contain package inputs.
4796 @item --search-paths
4797 Display the environment variable definitions that make up the
4800 @item --system=@var{system}
4801 @itemx -s @var{system}
4802 Attempt to build for @var{system}---e.g., @code{i686-linux}.
4807 Run @var{command} within an isolated container. The current working
4808 directory outside the container is mapped to @file{/env} inside the
4809 container. Additionally, the spawned process runs as the current user
4810 outside the container, but has root privileges in the context of the
4815 For containers, share the network namespace with the host system.
4816 Containers created without this flag only have access to the loopback
4819 @item --expose=@var{source}[=@var{target}]
4820 For containers, expose the file system @var{source} from the host system
4821 as the read-only file system @var{target} within the container. If
4822 @var{target} is not specified, @var{source} is used as the target mount
4823 point in the container.
4825 The example below spawns a Guile REPL in a container in which the user's
4826 home directory is accessible read-only via the @file{/exchange}
4830 guix environment --container --expose=$HOME=/exchange guile -- guile
4834 For containers, share the file system @var{source} from the host system
4835 as the writable file system @var{target} within the container. If
4836 @var{target} is not specified, @var{source} is used as the target mount
4837 point in the container.
4839 The example below spawns a Guile REPL in a container in which the user's
4840 home directory is accessible for both reading and writing via the
4841 @file{/exchange} directory:
4844 guix environment --container --share=$HOME=/exchange guile -- guile
4848 It also supports all of the common build options that @command{guix
4849 build} supports (@pxref{Invoking guix build, common build options}).
4851 @node Invoking guix publish
4852 @section Invoking @command{guix publish}
4854 The purpose of @command{guix publish} is to enable users to easily share
4855 their store with others, which can then use it as a substitute server
4856 (@pxref{Substitutes}).
4858 When @command{guix publish} runs, it spawns an HTTP server which allows
4859 anyone with network access to obtain substitutes from it. This means
4860 that any machine running Guix can also act as if it were a build farm,
4861 since the HTTP interface is compatible with Hydra, the software behind
4862 the @code{hydra.gnu.org} build farm.
4864 For security, each substitute is signed, allowing recipients to check
4865 their authenticity and integrity (@pxref{Substitutes}). Because
4866 @command{guix publish} uses the system's signing key, which is only
4867 readable by the system administrator, it must be started as root; the
4868 @code{--user} option makes it drop root privileges early on.
4870 The general syntax is:
4873 guix publish @var{options}@dots{}
4876 Running @command{guix publish} without any additional arguments will
4877 spawn an HTTP server on port 8080:
4883 Once a publishing server has been authorized (@pxref{Invoking guix
4884 archive}), the daemon may download substitutes from it:
4887 guix-daemon --substitute-urls=http://example.org:8080
4890 The following options are available:
4893 @item --port=@var{port}
4894 @itemx -p @var{port}
4895 Listen for HTTP requests on @var{port}.
4897 @item --listen=@var{host}
4898 Listen on the network interface for @var{host}. The default is to
4899 accept connections from any interface.
4901 @item --user=@var{user}
4902 @itemx -u @var{user}
4903 Change privileges to @var{user} as soon as possible---i.e., once the
4904 server socket is open and the signing key has been read.
4906 @item --repl[=@var{port}]
4907 @itemx -r [@var{port}]
4908 Spawn a Guile REPL server (@pxref{REPL Servers,,, guile, GNU Guile
4909 Reference Manual}) on @var{port} (37146 by default). This is used
4910 primarily for debugging a running @command{guix publish} server.
4914 @node Invoking guix challenge
4915 @section Invoking @command{guix challenge}
4917 @cindex reproducible builds
4918 @cindex verifiable builds
4920 Do the binaries provided by this server really correspond to the source
4921 code it claims to build? Is this package's build process deterministic?
4922 These are the questions the @command{guix challenge} command attempts to
4925 The former is obviously an important question: Before using a substitute
4926 server (@pxref{Substitutes}), you'd rather @emph{verify} that it
4927 provides the right binaries, and thus @emph{challenge} it. The latter
4928 is what enables the former: If package builds are deterministic, then
4929 independent builds of the package should yield the exact same result,
4930 bit for bit; if a server provides a binary different from the one
4931 obtained locally, it may be either corrupt or malicious.
4933 We know that the hash that shows up in @file{/gnu/store} file names is
4934 the hash of all the inputs of the process that built the file or
4935 directory---compilers, libraries, build scripts,
4936 etc. (@pxref{Introduction}). Assuming deterministic build processes,
4937 one store file name should map to exactly one build output.
4938 @command{guix challenge} checks whether there is, indeed, a single
4939 mapping by comparing the build outputs of several independent builds of
4940 any given store item.
4942 The command's output looks like this:
4945 $ guix challenge --substitute-urls="http://hydra.gnu.org http://guix.example.org"
4946 updating list of substitutes from 'http://hydra.gnu.org'... 100.0%
4947 updating list of substitutes from 'http://guix.example.org'... 100.0%
4948 /gnu/store/@dots{}-openssl-1.0.2d contents differ:
4949 local hash: 0725l22r5jnzazaacncwsvp9kgf42266ayyp814v7djxs7nk963q
4950 http://hydra.gnu.org/nar/@dots{}-openssl-1.0.2d: 0725l22r5jnzazaacncwsvp9kgf42266ayyp814v7djxs7nk963q
4951 http://guix.example.org/nar/@dots{}-openssl-1.0.2d: 1zy4fmaaqcnjrzzajkdn3f5gmjk754b43qkq47llbyak9z0qjyim
4952 /gnu/store/@dots{}-git-2.5.0 contents differ:
4953 local hash: 00p3bmryhjxrhpn2gxs2fy0a15lnip05l97205pgbk5ra395hyha
4954 http://hydra.gnu.org/nar/@dots{}-git-2.5.0: 069nb85bv4d4a6slrwjdy8v1cn4cwspm3kdbmyb81d6zckj3nq9f
4955 http://guix.example.org/nar/@dots{}-git-2.5.0: 0mdqa9w1p6cmli6976v4wi0sw9r4p5prkj7lzfd1877wk11c9c73
4956 /gnu/store/@dots{}-pius-2.1.1 contents differ:
4957 local hash: 0k4v3m9z1zp8xzzizb7d8kjj72f9172xv078sq4wl73vnq9ig3ax
4958 http://hydra.gnu.org/nar/@dots{}-pius-2.1.1: 0k4v3m9z1zp8xzzizb7d8kjj72f9172xv078sq4wl73vnq9ig3ax
4959 http://guix.example.org/nar/@dots{}-pius-2.1.1: 1cy25x1a4fzq5rk0pmvc8xhwyffnqz95h2bpvqsz2mpvlbccy0gs
4963 In this example, @command{guix challenge} first scans the store to
4964 determine the set of locally-built derivations---as opposed to store
4965 items that were downloaded from a substitute server---and then queries
4966 all the substitute servers. It then reports those store items for which
4967 the servers obtained a result different from the local build.
4969 @cindex non-determinism, in package builds
4970 As an example, @code{guix.example.org} always gets a different answer.
4971 Conversely, @code{hydra.gnu.org} agrees with local builds, except in the
4972 case of Git. This might indicate that the build process of Git is
4973 non-deterministic, meaning that its output varies as a function of
4974 various things that Guix does not fully control, in spite of building
4975 packages in isolated environments (@pxref{Features}). Most common
4976 sources of non-determinism include the addition of timestamps in build
4977 results, the inclusion of random numbers, and directory listings sorted
4978 by inode number. See @uref{http://reproducible.debian.net/howto/}, for
4981 To find out what's wrong with this Git binary, we can do something along
4982 these lines (@pxref{Invoking guix archive}):
4985 $ wget -q -O - http://hydra.gnu.org/nar/@dots{}-git-2.5.0 \
4986 | guix archive -x /tmp/git
4987 $ diff -ur /gnu/store/@dots{}-git.2.5.0 /tmp/git
4990 This command shows the difference between the files resulting from the
4991 local build, and the files resulting from the build on
4992 @code{hydra.gnu.org} (@pxref{Overview, Comparing and Merging Files,,
4993 diffutils, Comparing and Merging Files}). The @command{diff} command
4994 works great for text files. When binary files differ, a better option
4995 is @uref{http://diffoscope.org/, Diffoscope}, a tool that helps
4996 visualize differences for all kinds of files.
4998 Once you've done that work, you can tell whether the differences are due
4999 to a non-deterministic build process or to a malicious server. We try
5000 hard to remove sources of non-determinism in packages to make it easier
5001 to verify substitutes, but of course, this is a process, one that
5002 involves not just Guix but a large part of the free software community.
5003 In the meantime, @command{guix challenge} is one tool to help address
5006 If you are writing packages for Guix, you are encouraged to check
5007 whether @code{hydra.gnu.org} and other substitute servers obtain the
5008 same build result as you did with:
5011 $ guix challenge @var{package}
5015 ... where @var{package} is a package specification such as
5016 @code{guile-2.0} or @code{glibc:debug}.
5018 The general syntax is:
5021 guix challenge @var{options} [@var{packages}@dots{}]
5024 The one option that matters is:
5028 @item --substitute-urls=@var{urls}
5029 Consider @var{urls} the whitespace-separated list of substitute source
5035 @c *********************************************************************
5036 @node GNU Distribution
5037 @chapter GNU Distribution
5039 @cindex Guix System Distribution
5041 Guix comes with a distribution of the GNU system consisting entirely of
5042 free software@footnote{The term ``free'' here refers to the
5043 @url{http://www.gnu.org/philosophy/free-sw.html,freedom provided to
5044 users of that software}.}. The
5045 distribution can be installed on its own (@pxref{System Installation}),
5046 but it is also possible to install Guix as a package manager on top of
5047 an installed GNU/Linux system (@pxref{Installation}). To distinguish
5048 between the two, we refer to the standalone distribution as the Guix
5049 System Distribution, or GuixSD.
5051 The distribution provides core GNU packages such as GNU libc, GCC, and
5052 Binutils, as well as many GNU and non-GNU applications. The complete
5053 list of available packages can be browsed
5054 @url{http://www.gnu.org/software/guix/packages,on-line} or by
5055 running @command{guix package} (@pxref{Invoking guix package}):
5058 guix package --list-available
5061 Our goal has been to provide a practical 100% free software distribution of
5062 Linux-based and other variants of GNU, with a focus on the promotion and
5063 tight integration of GNU components, and an emphasis on programs and
5064 tools that help users exert that freedom.
5066 Packages are currently available on the following platforms:
5071 Intel/AMD @code{x86_64} architecture, Linux-Libre kernel;
5074 Intel 32-bit architecture (IA32), Linux-Libre kernel;
5077 ARMv7-A architecture with hard float, Thumb-2 and NEON,
5078 using the EABI hard-float ABI, and Linux-Libre kernel.
5080 @item mips64el-linux
5081 little-endian 64-bit MIPS processors, specifically the Loongson series,
5082 n32 application binary interface (ABI), and Linux-Libre kernel.
5086 GuixSD itself is currently only available on @code{i686} and @code{x86_64}.
5089 For information on porting to other architectures or kernels,
5093 * System Installation:: Installing the whole operating system.
5094 * System Configuration:: Configuring the operating system.
5095 * Installing Debugging Files:: Feeding the debugger.
5096 * Security Updates:: Deploying security fixes quickly.
5097 * Package Modules:: Packages from the programmer's viewpoint.
5098 * Packaging Guidelines:: Growing the distribution.
5099 * Bootstrapping:: GNU/Linux built from scratch.
5100 * Porting:: Targeting another platform or kernel.
5103 Building this distribution is a cooperative effort, and you are invited
5104 to join! @xref{Contributing}, for information about how you can help.
5106 @node System Installation
5107 @section System Installation
5109 @cindex Guix System Distribution
5110 This section explains how to install the Guix System Distribution
5111 on a machine. The Guix package manager can
5112 also be installed on top of a running GNU/Linux system,
5113 @pxref{Installation}.
5116 @c This paragraph is for people reading this from tty2 of the
5117 @c installation image.
5118 You're reading this documentation with an Info reader. For details on
5119 how to use it, hit the @key{RET} key (``return'' or ``enter'') on the
5120 link that follows: @pxref{Help,,, info, Info: An Introduction}. Hit
5121 @kbd{l} afterwards to come back here.
5124 @subsection Limitations
5126 As of version @value{VERSION}, the Guix System Distribution (GuixSD) is
5127 not production-ready. It may contain bugs and lack important
5128 features. Thus, if you are looking for a stable production system that
5129 respects your freedom as a computer user, a good solution at this point
5130 is to consider @url{http://www.gnu.org/distros/free-distros.html, one of
5131 more established GNU/Linux distributions}. We hope you can soon switch
5132 to the GuixSD without fear, of course. In the meantime, you can
5133 also keep using your distribution and try out the package manager on top
5134 of it (@pxref{Installation}).
5136 Before you proceed with the installation, be aware of the following
5137 noteworthy limitations applicable to version @value{VERSION}:
5141 The installation process does not include a graphical user interface and
5142 requires familiarity with GNU/Linux (see the following subsections to
5143 get a feel of what that means.)
5146 The system does not yet provide full GNOME and KDE desktops. Xfce and
5147 Enlightenment are available though, if graphical desktop environments
5148 are your thing, as well as a number of X11 window managers.
5151 Support for the Logical Volume Manager (LVM) is missing.
5154 Few system services are currently supported out-of-the-box
5158 More than 2,000 packages are available, but you may
5159 occasionally find that a useful package is missing.
5162 You've been warned. But more than a disclaimer, this is an invitation
5163 to report issues (and success stories!), and join us in improving it.
5164 @xref{Contributing}, for more info.
5166 @subsection USB Stick Installation
5168 An installation image for USB sticks can be downloaded from
5169 @indicateurl{ftp://alpha.gnu.org/gnu/guix/guixsd-usb-install-@value{VERSION}.@var{system}.xz},
5170 where @var{system} is one of:
5174 for a GNU/Linux system on Intel/AMD-compatible 64-bit CPUs;
5177 for a 32-bit GNU/Linux system on Intel-compatible CPUs.
5180 This image contains a single partition with the tools necessary for an
5181 installation. It is meant to be copied @emph{as is} to a large-enough
5184 To copy the image to a USB stick, follow these steps:
5188 Decompress the image using the @command{xz} command:
5191 xz -d guixsd-usb-install-@value{VERSION}.@var{system}.xz
5195 Insert a USB stick of 1@tie{}GiB or more in your machine, and determine
5196 its device name. Assuming that USB stick is known as @file{/dev/sdX},
5197 copy the image with:
5200 dd if=guixsd-usb-install-@value{VERSION}.x86_64 of=/dev/sdX
5203 Access to @file{/dev/sdX} usually requires root privileges.
5206 Once this is done, you should be able to reboot the system and boot from
5207 the USB stick. The latter usually requires you to get in the BIOS' boot
5208 menu, where you can choose to boot from the USB stick.
5210 @subsection Preparing for Installation
5212 Once you have successfully booted the image on the USB stick, you should
5213 end up with a root prompt. Several console TTYs are configured and can
5214 be used to run commands as root. TTY2 shows this documentation,
5215 browsable using the Info reader commands (@pxref{Help,,, info, Info: An
5218 To install the system, you would:
5223 Configure the network, by running @command{ifconfig eno1 up && dhclient
5224 eno1} (to get an automatically assigned IP address from the wired
5225 network interface controller@footnote{
5226 @c http://cgit.freedesktop.org/systemd/systemd/tree/src/udev/udev-builtin-net_id.c#n20
5227 The name @code{eno1} is for the first on-board Ethernet controller. The
5228 interface name for an Ethernet controller that is in the first slot of
5229 the first PCI bus, for instance, would be @code{enp1s0}. Use
5230 @command{ifconfig -a} to list all the available network interfaces.}),
5231 or using the @command{ifconfig} command.
5233 The system automatically loads drivers for your network interface
5236 Setting up network access is almost always a requirement because the
5237 image does not contain all the software and tools that may be needed.
5240 Unless this has already been done, you must partition and format the
5243 Preferably, assign partitions a label so that you can easily and
5244 reliably refer to them in @code{file-system} declarations (@pxref{File
5245 Systems}). This is typically done using the @code{-L} option of
5246 @command{mkfs.ext4} and related commands.
5248 The installation image includes Parted (@pxref{Overview,,, parted, GNU
5249 Parted User Manual}), @command{fdisk}, Cryptsetup/LUKS for disk
5250 encryption, and e2fsprogs, the suite of tools to manipulate
5251 ext2/ext3/ext4 file systems.
5254 Once that is done, mount the target root partition under @file{/mnt}.
5257 Lastly, run @code{deco start cow-store /mnt}.
5259 This will make @file{/gnu/store} copy-on-write, such that packages added
5260 to it during the installation phase will be written to the target disk
5261 rather than kept in memory.
5266 @subsection Proceeding with the Installation
5268 With the target partitions ready, you now have to edit a file and
5269 provide the declaration of the operating system to be installed. To
5270 that end, the installation system comes with two text editors: GNU nano
5271 (@pxref{Top,,, nano, GNU nano Manual}), and GNU Zile, an Emacs clone.
5272 It is better to store that file on the target root file system, say, as
5273 @file{/mnt/etc/config.scm}.
5275 @xref{Using the Configuration System}, for examples of operating system
5276 configurations. These examples are available under
5277 @file{/etc/configuration} in the installation image, so you can copy
5278 them and use them as a starting point for your own configuration.
5280 Once you are done preparing the configuration file, the new system must
5281 be initialized (remember that the target root file system is mounted
5285 guix system init /mnt/etc/config.scm /mnt
5289 This will copy all the necessary files, and install GRUB on
5290 @file{/dev/sdX}, unless you pass the @option{--no-grub} option. For
5291 more information, @pxref{Invoking guix system}. This command may trigger
5292 downloads or builds of missing packages, which can take some time.
5294 Once that command has completed---and hopefully succeeded!---you can run
5295 @command{reboot} and boot into the new system. The @code{root} password
5296 in the new system is initially empty; other users' passwords need to be
5297 initialized by running the @command{passwd} command as @code{root},
5298 unless your configuration specifies otherwise
5299 (@pxref{user-account-password, user account passwords}).
5301 Join us on @code{#guix} on the Freenode IRC network or on
5302 @file{guix-devel@@gnu.org} to share your experience---good or not so
5305 @subsection Building the Installation Image
5307 The installation image described above was built using the @command{guix
5308 system} command, specifically:
5311 guix system disk-image --image-size=850MiB gnu/system/install.scm
5314 @xref{Invoking guix system}, for more information. See
5315 @file{gnu/system/install.scm} in the source tree for more information
5316 about the installation image.
5318 @node System Configuration
5319 @section System Configuration
5321 @cindex system configuration
5322 The Guix System Distribution supports a consistent whole-system configuration
5323 mechanism. By that we mean that all aspects of the global system
5324 configuration---such as the available system services, timezone and
5325 locale settings, user accounts---are declared in a single place. Such
5326 a @dfn{system configuration} can be @dfn{instantiated}---i.e., effected.
5328 One of the advantages of putting all the system configuration under the
5329 control of Guix is that it supports transactional system upgrades, and
5330 makes it possible to roll-back to a previous system instantiation,
5331 should something go wrong with the new one (@pxref{Features}). Another
5332 one is that it makes it easy to replicate the exact same configuration
5333 across different machines, or at different points in time, without
5334 having to resort to additional administration tools layered on top of
5335 the system's own tools.
5336 @c Yes, we're talking of Puppet, Chef, & co. here. ↑
5338 This section describes this mechanism. First we focus on the system
5339 administrator's viewpoint---explaining how the system is configured and
5340 instantiated. Then we show how this mechanism can be extended, for
5341 instance to support new system services.
5344 * Using the Configuration System:: Customizing your GNU system.
5345 * operating-system Reference:: Detail of operating-system declarations.
5346 * File Systems:: Configuring file system mounts.
5347 * Mapped Devices:: Block device extra processing.
5348 * User Accounts:: Specifying user accounts.
5349 * Locales:: Language and cultural convention settings.
5350 * Services:: Specifying system services.
5351 * Setuid Programs:: Programs running with root privileges.
5352 * X.509 Certificates:: Authenticating HTTPS servers.
5353 * Name Service Switch:: Configuring libc's name service switch.
5354 * Initial RAM Disk:: Linux-Libre bootstrapping.
5355 * GRUB Configuration:: Configuring the boot loader.
5356 * Invoking guix system:: Instantiating a system configuration.
5357 * Defining Services:: Adding new service definitions.
5360 @node Using the Configuration System
5361 @subsection Using the Configuration System
5363 The operating system is configured by providing an
5364 @code{operating-system} declaration in a file that can then be passed to
5365 the @command{guix system} command (@pxref{Invoking guix system}). A
5366 simple setup, with the default system services, the default Linux-Libre
5367 kernel, initial RAM disk, and boot loader looks like this:
5369 @findex operating-system
5371 @include os-config-bare-bones.texi
5374 This example should be self-describing. Some of the fields defined
5375 above, such as @code{host-name} and @code{bootloader}, are mandatory.
5376 Others, such as @code{packages} and @code{services}, can be omitted, in
5377 which case they get a default value.
5379 @vindex %base-packages
5380 The @code{packages} field lists
5381 packages that will be globally visible on the system, for all user
5382 accounts---i.e., in every user's @code{PATH} environment variable---in
5383 addition to the per-user profiles (@pxref{Invoking guix package}). The
5384 @var{%base-packages} variable provides all the tools one would expect
5385 for basic user and administrator tasks---including the GNU Core
5386 Utilities, the GNU Networking Utilities, the GNU Zile lightweight text
5387 editor, @command{find}, @command{grep}, etc. The example above adds
5388 tcpdump to those, taken from the @code{(gnu packages admin)} module
5389 (@pxref{Package Modules}).
5391 @vindex %base-services
5392 The @code{services} field lists @dfn{system services} to be made
5393 available when the system starts (@pxref{Services}).
5394 The @code{operating-system} declaration above specifies that, in
5395 addition to the basic services, we want the @command{lshd} secure shell
5396 daemon listening on port 2222 (@pxref{Networking Services,
5397 @code{lsh-service}}). Under the hood,
5398 @code{lsh-service} arranges so that @code{lshd} is started with the
5399 right command-line options, possibly with supporting configuration files
5400 generated as needed (@pxref{Defining Services}).
5402 @cindex customization, of services
5403 @findex modify-services
5404 Occasionally, instead of using the base services as is, you will want to
5405 customize them. For instance, to change the configuration of
5406 @code{guix-daemon} and Mingetty (the console log-in), you may write the
5407 following instead of @var{%base-services}:
5410 (modify-services %base-services
5411 (guix-service-type config =>
5414 (use-substitutes? #f)
5415 (extra-options '("--gc-keep-outputs"))))
5416 (mingetty-service-type config =>
5417 (mingetty-configuration
5419 (motd (plain-file "motd" "Hi there!")))))
5423 The effect here is to change the options passed to @command{guix-daemon}
5424 when it is started, as well as the ``message of the day'' that appears
5425 when logging in at the console. @xref{Service Reference,
5426 @code{modify-services}}, for more on that.
5428 The configuration for a typical ``desktop'' usage, with the X11 display
5429 server, a desktop environment, network management, power management, and
5430 more, would look like this:
5433 @include os-config-desktop.texi
5436 @xref{Desktop Services}, for the exact list of services provided by
5437 @var{%desktop-services}. @xref{X.509 Certificates}, for background
5438 information about the @code{nss-certs} package that is used here.
5439 @xref{operating-system Reference}, for details about all the available
5440 @code{operating-system} fields.
5442 Assuming the above snippet is stored in the @file{my-system-config.scm}
5443 file, the @command{guix system reconfigure my-system-config.scm} command
5444 instantiates that configuration, and makes it the default GRUB boot
5445 entry (@pxref{Invoking guix system}).
5447 The normal way to change the system's configuration is by updating this
5448 file and re-running @command{guix system reconfigure}. One should never
5449 have to touch files in @command{/etc} or to run commands that modify the
5450 system state such as @command{useradd} or @command{grub-install}. In
5451 fact, you must avoid that since that would not only void your warranty
5452 but also prevent you from rolling back to previous versions of your
5453 system, should you ever need to.
5455 @cindex roll-back, of the operating system
5456 Speaking of roll-back, each time you run @command{guix system
5457 reconfigure}, a new @dfn{generation} of the system is created---without
5458 modifying or deleting previous generations. Old system generations get
5459 an entry in the GRUB boot menu, allowing you to boot them in case
5460 something went wrong with the latest generation. Reassuring, no? The
5461 @command{guix system list-generations} command lists the system
5462 generations available on disk.
5464 At the Scheme level, the bulk of an @code{operating-system} declaration
5465 is instantiated with the following monadic procedure (@pxref{The Store
5468 @deffn {Monadic Procedure} operating-system-derivation os
5469 Return a derivation that builds @var{os}, an @code{operating-system}
5470 object (@pxref{Derivations}).
5472 The output of the derivation is a single directory that refers to all
5473 the packages, configuration files, and other supporting files needed to
5474 instantiate @var{os}.
5477 @node operating-system Reference
5478 @subsection @code{operating-system} Reference
5480 This section summarizes all the options available in
5481 @code{operating-system} declarations (@pxref{Using the Configuration
5484 @deftp {Data Type} operating-system
5485 This is the data type representing an operating system configuration.
5486 By that, we mean all the global system configuration, not per-user
5487 configuration (@pxref{Using the Configuration System}).
5490 @item @code{kernel} (default: @var{linux-libre})
5491 The package object of the operating system kernel to use@footnote{Currently
5492 only the Linux-libre kernel is supported. In the future, it will be
5493 possible to use the GNU@tie{}Hurd.}.
5495 @item @code{kernel-arguments} (default: @code{'()})
5496 List of strings or gexps representing additional arguments to pass on
5497 the kernel's command-line---e.g., @code{("console=ttyS0")}.
5499 @item @code{bootloader}
5500 The system bootloader configuration object. @xref{GRUB Configuration}.
5502 @item @code{initrd} (default: @code{base-initrd})
5503 A two-argument monadic procedure that returns an initial RAM disk for
5504 the Linux kernel. @xref{Initial RAM Disk}.
5506 @item @code{firmware} (default: @var{%base-firmware})
5508 List of firmware packages loadable by the operating system kernel.
5510 The default includes firmware needed for Atheros-based WiFi devices
5511 (Linux-libre module @code{ath9k}.)
5513 @item @code{host-name}
5516 @item @code{hosts-file}
5518 A file-like object (@pxref{G-Expressions, file-like objects}) for use as
5519 @file{/etc/hosts} (@pxref{Host Names,,, libc, The GNU C Library
5520 Reference Manual}). The default is a file with entries for
5521 @code{localhost} and @var{host-name}.
5523 @item @code{mapped-devices} (default: @code{'()})
5524 A list of mapped devices. @xref{Mapped Devices}.
5526 @item @code{file-systems}
5527 A list of file systems. @xref{File Systems}.
5529 @item @code{swap-devices} (default: @code{'()})
5530 @cindex swap devices
5531 A list of strings identifying devices to be used for ``swap space''
5532 (@pxref{Memory Concepts,,, libc, The GNU C Library Reference Manual}).
5533 For example, @code{'("/dev/sda3")}.
5535 @item @code{users} (default: @code{%base-user-accounts})
5536 @itemx @code{groups} (default: @var{%base-groups})
5537 List of user accounts and groups. @xref{User Accounts}.
5539 @item @code{skeletons} (default: @code{(default-skeletons)})
5540 A monadic list of pairs of target file name and files. These are the
5541 files that will be used as skeletons as new accounts are created.
5543 For instance, a valid value may look like this:
5546 (mlet %store-monad ((bashrc (text-file "bashrc" "\
5547 export PATH=$HOME/.guix-profile/bin")))
5548 (return `((".bashrc" ,bashrc))))
5551 @item @code{issue} (default: @var{%default-issue})
5552 A string denoting the contents of the @file{/etc/issue} file, which is
5553 what displayed when users log in on a text console.
5555 @item @code{packages} (default: @var{%base-packages})
5556 The set of packages installed in the global profile, which is accessible
5557 at @file{/run/current-system/profile}.
5559 The default set includes core utilities, but it is good practice to
5560 install non-core utilities in user profiles (@pxref{Invoking guix
5563 @item @code{timezone}
5564 A timezone identifying string---e.g., @code{"Europe/Paris"}.
5566 @item @code{locale} (default: @code{"en_US.utf8"})
5567 The name of the default locale (@pxref{Locale Names,,, libc, The GNU C
5568 Library Reference Manual}). @xref{Locales}, for more information.
5570 @item @code{locale-definitions} (default: @var{%default-locale-definitions})
5571 The list of locale definitions to be compiled and that may be used at
5572 run time. @xref{Locales}.
5574 @item @code{locale-libcs} (default: @code{(list @var{glibc})})
5575 The list of GNU@tie{}libc packages whose locale data and tools are used
5576 to build the locale definitions. @xref{Locales}, for compatibility
5577 considerations that justify this option.
5579 @item @code{name-service-switch} (default: @var{%default-nss})
5580 Configuration of libc's name service switch (NSS)---a
5581 @code{<name-service-switch>} object. @xref{Name Service Switch}, for
5584 @item @code{services} (default: @var{%base-services})
5585 A list of monadic values denoting system services. @xref{Services}.
5587 @item @code{pam-services} (default: @code{(base-pam-services)})
5589 @cindex pluggable authentication modules
5590 Linux @dfn{pluggable authentication module} (PAM) services.
5591 @c FIXME: Add xref to PAM services section.
5593 @item @code{setuid-programs} (default: @var{%setuid-programs})
5594 List of string-valued G-expressions denoting setuid programs.
5595 @xref{Setuid Programs}.
5597 @item @code{sudoers-file} (default: @var{%sudoers-specification})
5598 @cindex sudoers file
5599 The contents of the @file{/etc/sudoers} file as a file-like object
5600 (@pxref{G-Expressions, @code{local-file} and @code{plain-file}}).
5602 This file specifies which users can use the @command{sudo} command, what
5603 they are allowed to do, and what privileges they may gain. The default
5604 is that only @code{root} and members of the @code{wheel} group may use
5611 @subsection File Systems
5613 The list of file systems to be mounted is specified in the
5614 @code{file-systems} field of the operating system's declaration
5615 (@pxref{Using the Configuration System}). Each file system is declared
5616 using the @code{file-system} form, like this:
5620 (mount-point "/home")
5621 (device "/dev/sda3")
5625 As usual, some of the fields are mandatory---those shown in the example
5626 above---while others can be omitted. These are described below.
5628 @deftp {Data Type} file-system
5629 Objects of this type represent file systems to be mounted. They
5630 contain the following members:
5634 This is a string specifying the type of the file system---e.g.,
5637 @item @code{mount-point}
5638 This designates the place where the file system is to be mounted.
5641 This names the ``source'' of the file system. By default it is the name
5642 of a node under @file{/dev}, but its meaning depends on the @code{title}
5643 field described below.
5645 @item @code{title} (default: @code{'device})
5646 This is a symbol that specifies how the @code{device} field is to be
5649 When it is the symbol @code{device}, then the @code{device} field is
5650 interpreted as a file name; when it is @code{label}, then @code{device}
5651 is interpreted as a partition label name; when it is @code{uuid},
5652 @code{device} is interpreted as a partition unique identifier (UUID).
5654 UUIDs may be converted from their string representation (as shown by the
5655 @command{tune2fs -l} command) using the @code{uuid} form, like this:
5659 (mount-point "/home")
5662 (device (uuid "4dab5feb-d176-45de-b287-9b0a6e4c01cb")))
5665 The @code{label} and @code{uuid} options offer a way to refer to disk
5666 partitions without having to hard-code their actual device
5667 name@footnote{Note that, while it is tempting to use
5668 @file{/dev/disk/by-uuid} and similar device names to achieve the same
5669 result, this is not recommended: These special device nodes are created
5670 by the udev daemon and may be unavailable at the time the device is
5673 However, when a file system's source is a mapped device (@pxref{Mapped
5674 Devices}), its @code{device} field @emph{must} refer to the mapped
5675 device name---e.g., @file{/dev/mapper/root-partition}---and consequently
5676 @code{title} must be set to @code{'device}. This is required so that
5677 the system knows that mounting the file system depends on having the
5678 corresponding device mapping established.
5680 @item @code{flags} (default: @code{'()})
5681 This is a list of symbols denoting mount flags. Recognized flags
5682 include @code{read-only}, @code{bind-mount}, @code{no-dev} (disallow
5683 access to special files), @code{no-suid} (ignore setuid and setgid
5684 bits), and @code{no-exec} (disallow program execution.)
5686 @item @code{options} (default: @code{#f})
5687 This is either @code{#f}, or a string denoting mount options.
5689 @item @code{needed-for-boot?} (default: @code{#f})
5690 This Boolean value indicates whether the file system is needed when
5691 booting. If that is true, then the file system is mounted when the
5692 initial RAM disk (initrd) is loaded. This is always the case, for
5693 instance, for the root file system.
5695 @item @code{check?} (default: @code{#t})
5696 This Boolean indicates whether the file system needs to be checked for
5697 errors before being mounted.
5699 @item @code{create-mount-point?} (default: @code{#f})
5700 When true, the mount point is created if it does not exist yet.
5702 @item @code{dependencies} (default: @code{'()})
5703 This is a list of @code{<file-system>} objects representing file systems
5704 that must be mounted before (and unmounted after) this one.
5706 As an example, consider a hierarchy of mounts: @file{/sys/fs/cgroup} is
5707 a dependency of @file{/sys/fs/cgroup/cpu} and
5708 @file{/sys/fs/cgroup/memory}.
5713 The @code{(gnu system file-systems)} exports the following useful
5716 @defvr {Scheme Variable} %base-file-systems
5717 These are essential file systems that are required on normal systems,
5718 such as @var{%pseudo-terminal-file-system} and @var{%immutable-store} (see
5719 below.) Operating system declarations should always contain at least
5723 @defvr {Scheme Variable} %pseudo-terminal-file-system
5724 This is the file system to be mounted as @file{/dev/pts}. It supports
5725 @dfn{pseudo-terminals} created @i{via} @code{openpty} and similar
5726 functions (@pxref{Pseudo-Terminals,,, libc, The GNU C Library Reference
5727 Manual}). Pseudo-terminals are used by terminal emulators such as
5731 @defvr {Scheme Variable} %shared-memory-file-system
5732 This file system is mounted as @file{/dev/shm} and is used to support
5733 memory sharing across processes (@pxref{Memory-mapped I/O,
5734 @code{shm_open},, libc, The GNU C Library Reference Manual}).
5737 @defvr {Scheme Variable} %immutable-store
5738 This file system performs a read-only ``bind mount'' of
5739 @file{/gnu/store}, making it read-only for all the users including
5740 @code{root}. This prevents against accidental modification by software
5741 running as @code{root} or by system administrators.
5743 The daemon itself is still able to write to the store: it remounts it
5744 read-write in its own ``name space.''
5747 @defvr {Scheme Variable} %binary-format-file-system
5748 The @code{binfmt_misc} file system, which allows handling of arbitrary
5749 executable file types to be delegated to user space. This requires the
5750 @code{binfmt.ko} kernel module to be loaded.
5753 @defvr {Scheme Variable} %fuse-control-file-system
5754 The @code{fusectl} file system, which allows unprivileged users to mount
5755 and unmount user-space FUSE file systems. This requires the
5756 @code{fuse.ko} kernel module to be loaded.
5759 @node Mapped Devices
5760 @subsection Mapped Devices
5762 @cindex device mapping
5763 @cindex mapped devices
5764 The Linux kernel has a notion of @dfn{device mapping}: a block device,
5765 such as a hard disk partition, can be @dfn{mapped} into another device,
5766 with additional processing over the data that flows through
5767 it@footnote{Note that the GNU@tie{}Hurd makes no difference between the
5768 concept of a ``mapped device'' and that of a file system: both boil down
5769 to @emph{translating} input/output operations made on a file to
5770 operations on its backing store. Thus, the Hurd implements mapped
5771 devices, like file systems, using the generic @dfn{translator} mechanism
5772 (@pxref{Translators,,, hurd, The GNU Hurd Reference Manual}).}. A
5773 typical example is encryption device mapping: all writes to the mapped
5774 device are encrypted, and all reads are deciphered, transparently.
5776 Mapped devices are declared using the @code{mapped-device} form:
5780 (source "/dev/sda3")
5782 (type luks-device-mapping))
5786 @cindex disk encryption
5788 This example specifies a mapping from @file{/dev/sda3} to
5789 @file{/dev/mapper/home} using LUKS---the
5790 @url{http://code.google.com/p/cryptsetup,Linux Unified Key Setup}, a
5791 standard mechanism for disk encryption. The @file{/dev/mapper/home}
5792 device can then be used as the @code{device} of a @code{file-system}
5793 declaration (@pxref{File Systems}). The @code{mapped-device} form is
5796 @deftp {Data Type} mapped-device
5797 Objects of this type represent device mappings that will be made when
5798 the system boots up.
5802 This string specifies the name of the block device to be mapped, such as
5806 This string specifies the name of the mapping to be established. For
5807 example, specifying @code{"my-partition"} will lead to the creation of
5808 the @code{"/dev/mapper/my-partition"} device.
5811 This must be a @code{mapped-device-kind} object, which specifies how
5812 @var{source} is mapped to @var{target}.
5816 @defvr {Scheme Variable} luks-device-mapping
5817 This defines LUKS block device encryption using the @command{cryptsetup}
5818 command, from the same-named package. This relies on the
5819 @code{dm-crypt} Linux kernel module.
5823 @subsection User Accounts
5825 User accounts and groups are entirely managed through the
5826 @code{operating-system} declaration. They are specified with the
5827 @code{user-account} and @code{user-group} forms:
5833 (supplementary-groups '("wheel" ;allow use of sudo, etc.
5835 "video" ;video devices such as webcams
5836 "cdrom")) ;the good ol' CD-ROM
5837 (comment "Bob's sister")
5838 (home-directory "/home/alice"))
5841 When booting or upon completion of @command{guix system reconfigure},
5842 the system ensures that only the user accounts and groups specified in
5843 the @code{operating-system} declaration exist, and with the specified
5844 properties. Thus, account or group creations or modifications made by
5845 directly invoking commands such as @command{useradd} are lost upon
5846 reconfiguration or reboot. This ensures that the system remains exactly
5849 @deftp {Data Type} user-account
5850 Objects of this type represent user accounts. The following members may
5855 The name of the user account.
5858 This is the name (a string) or identifier (a number) of the user group
5859 this account belongs to.
5861 @item @code{supplementary-groups} (default: @code{'()})
5862 Optionally, this can be defined as a list of group names that this
5865 @item @code{uid} (default: @code{#f})
5866 This is the user ID for this account (a number), or @code{#f}. In the
5867 latter case, a number is automatically chosen by the system when the
5870 @item @code{comment} (default: @code{""})
5871 A comment about the account, such as the account's owner full name.
5873 @item @code{home-directory}
5874 This is the name of the home directory for the account.
5876 @item @code{shell} (default: Bash)
5877 This is a G-expression denoting the file name of a program to be used as
5878 the shell (@pxref{G-Expressions}).
5880 @item @code{system?} (default: @code{#f})
5881 This Boolean value indicates whether the account is a ``system''
5882 account. System accounts are sometimes treated specially; for instance,
5883 graphical login managers do not list them.
5885 @anchor{user-account-password}
5886 @item @code{password} (default: @code{#f})
5887 You would normally leave this field to @code{#f}, initialize user
5888 passwords as @code{root} with the @command{passwd} command, and then let
5889 users change it with @command{passwd}. Passwords set with
5890 @command{passwd} are of course preserved across reboot and
5893 If you @emph{do} want to have a preset password for an account, then
5894 this field must contain the encrypted password, as a string.
5895 @xref{crypt,,, libc, The GNU C Library Reference Manual}, for more information
5896 on password encryption, and @ref{Encryption,,, guile, GNU Guile Reference
5897 Manual}, for information on Guile's @code{crypt} procedure.
5902 User group declarations are even simpler:
5905 (user-group (name "students"))
5908 @deftp {Data Type} user-group
5909 This type is for, well, user groups. There are just a few fields:
5915 @item @code{id} (default: @code{#f})
5916 The group identifier (a number). If @code{#f}, a new number is
5917 automatically allocated when the group is created.
5919 @item @code{system?} (default: @code{#f})
5920 This Boolean value indicates whether the group is a ``system'' group.
5921 System groups have low numerical IDs.
5923 @item @code{password} (default: @code{#f})
5924 What, user groups can have a password? Well, apparently yes. Unless
5925 @code{#f}, this field specifies the group's password.
5930 For convenience, a variable lists all the basic user groups one may
5933 @defvr {Scheme Variable} %base-groups
5934 This is the list of basic user groups that users and/or packages expect
5935 to be present on the system. This includes groups such as ``root'',
5936 ``wheel'', and ``users'', as well as groups used to control access to
5937 specific devices such as ``audio'', ``disk'', and ``cdrom''.
5940 @defvr {Scheme Variable} %base-user-accounts
5941 This is the list of basic system accounts that programs may expect to
5942 find on a GNU/Linux system, such as the ``nobody'' account.
5944 Note that the ``root'' account is not included here. It is a
5945 special-case and is automatically added whether or not it is specified.
5952 A @dfn{locale} defines cultural conventions for a particular language
5953 and region of the world (@pxref{Locales,,, libc, The GNU C Library
5954 Reference Manual}). Each locale has a name that typically has the form
5955 @code{@var{language}_@var{territory}.@var{codeset}}---e.g.,
5956 @code{fr_LU.utf8} designates the locale for the French language, with
5957 cultural conventions from Luxembourg, and using the UTF-8 encoding.
5959 @cindex locale definition
5960 Usually, you will want to specify the default locale for the machine
5961 using the @code{locale} field of the @code{operating-system} declaration
5962 (@pxref{operating-system Reference, @code{locale}}).
5964 That locale must be among the @dfn{locale definitions} that are known to
5965 the system---and these are specified in the @code{locale-definitions}
5966 slot of @code{operating-system}. The default value includes locale
5967 definition for some widely used locales, but not for all the available
5968 locales, in order to save space.
5970 If the locale specified in the @code{locale} field is not among the
5971 definitions listed in @code{locale-definitions}, @command{guix system}
5972 raises an error. In that case, you should add the locale definition to
5973 the @code{locale-definitions} field. For instance, to add the North
5974 Frisian locale for Germany, the value of that field may be:
5977 (cons (locale-definition
5978 (name "fy_DE.utf8") (source "fy_DE"))
5979 %default-locale-definitions)
5982 Likewise, to save space, one might want @code{locale-definitions} to
5983 list only the locales that are actually used, as in:
5986 (list (locale-definition
5987 (name "ja_JP.eucjp") (source "ja_JP")
5988 (charset "EUC-JP")))
5992 The compiled locale definitions are available at
5993 @file{/run/current-system/locale/X.Y}, where @code{X.Y} is the libc
5994 version, which is the default location where the GNU@tie{}libc provided
5995 by Guix looks for locale data. This can be overridden using the
5996 @code{LOCPATH} environment variable (@pxref{locales-and-locpath,
5997 @code{LOCPATH} and locale packages}).
5999 The @code{locale-definition} form is provided by the @code{(gnu system
6000 locale)} module. Details are given below.
6002 @deftp {Data Type} locale-definition
6003 This is the data type of a locale definition.
6008 The name of the locale. @xref{Locale Names,,, libc, The GNU C Library
6009 Reference Manual}, for more information on locale names.
6012 The name of the source for that locale. This is typically the
6013 @code{@var{language}_@var{territory}} part of the locale name.
6015 @item @code{charset} (default: @code{"UTF-8"})
6016 The ``character set'' or ``code set'' for that locale,
6017 @uref{http://www.iana.org/assignments/character-sets, as defined by
6023 @defvr {Scheme Variable} %default-locale-definitions
6024 An arbitrary list of commonly used UTF-8 locales, used as the default
6025 value of the @code{locale-definitions} field of @code{operating-system}
6029 @cindex normalized codeset in locale names
6030 These locale definitions use the @dfn{normalized codeset} for the part
6031 that follows the dot in the name (@pxref{Using gettextized software,
6032 normalized codeset,, libc, The GNU C Library Reference Manual}). So for
6033 instance it has @code{uk_UA.utf8} but @emph{not}, say,
6037 @subsubsection Locale Data Compatibility Considerations
6039 @cindex incompatibility, of locale data
6040 @code{operating-system} declarations provide a @code{locale-libcs} field
6041 to specify the GNU@tie{}libc packages that are used to compile locale
6042 declarations (@pxref{operating-system Reference}). ``Why would I
6043 care?'', you may ask. Well, it turns out that the binary format of
6044 locale data is occasionally incompatible from one libc version to
6047 @c See <https://sourceware.org/ml/libc-alpha/2015-09/msg00575.html>
6048 @c and <https://lists.gnu.org/archive/html/guix-devel/2015-08/msg00737.html>.
6049 For instance, a program linked against libc version 2.21 is unable to
6050 read locale data produced with libc 2.22; worse, that program
6051 @emph{aborts} instead of simply ignoring the incompatible locale
6052 data@footnote{Versions 2.23 and later of GNU@tie{}libc will simply skip
6053 the incompatible locale data, which is already an improvement.}.
6054 Similarly, a program linked against libc 2.22 can read most, but not
6055 all, the locale data from libc 2.21 (specifically, @code{LC_COLLATE}
6056 data is incompatible); thus calls to @code{setlocale} may fail, but
6057 programs will not abort.
6059 The ``problem'' in GuixSD is that users have a lot of freedom: They can
6060 choose whether and when to upgrade software in their profiles, and might
6061 be using a libc version different from the one the system administrator
6062 used to build the system-wide locale data.
6064 Fortunately, unprivileged users can also install their own locale data
6065 and define @var{GUIX_LOCPATH} accordingly (@pxref{locales-and-locpath,
6066 @code{GUIX_LOCPATH} and locale packages}).
6068 Still, it is best if the system-wide locale data at
6069 @file{/run/current-system/locale} is built for all the libc versions
6070 actually in use on the system, so that all the programs can access
6071 it---this is especially crucial on a multi-user system. To do that, the
6072 administrator can specify several libc packages in the
6073 @code{locale-libcs} field of @code{operating-system}:
6076 (use-package-modules base)
6080 (locale-libcs (list glibc-2.21 (canonical-package glibc))))
6083 This example would lead to a system containing locale definitions for
6084 both libc 2.21 and the current version of libc in
6085 @file{/run/current-system/locale}.
6089 @subsection Services
6091 @cindex system services
6092 An important part of preparing an @code{operating-system} declaration is
6093 listing @dfn{system services} and their configuration (@pxref{Using the
6094 Configuration System}). System services are typically daemons launched
6095 when the system boots, or other actions needed at that time---e.g.,
6096 configuring network access.
6098 Services are managed by GNU@tie{}dmd (@pxref{Introduction,,, dmd, GNU
6099 dmd Manual}). On a running system, the @command{deco} command allows
6100 you to list the available services, show their status, start and stop
6101 them, or do other specific operations (@pxref{Jump Start,,, dmd, GNU dmd
6102 Manual}). For example:
6108 The above command, run as @code{root}, lists the currently defined
6109 services. The @command{deco doc} command shows a synopsis of the given
6114 Run libc's name service cache daemon (nscd).
6117 The @command{start}, @command{stop}, and @command{restart} sub-commands
6118 have the effect you would expect. For instance, the commands below stop
6119 the nscd service and restart the Xorg display server:
6123 Service nscd has been stopped.
6124 # deco restart xorg-server
6125 Service xorg-server has been stopped.
6126 Service xorg-server has been started.
6129 The following sections document the available services, starting with
6130 the core services, that may be used in an @code{operating-system}
6134 * Base Services:: Essential system services.
6135 * Networking Services:: Network setup, SSH daemon, etc.
6136 * X Window:: Graphical display.
6137 * Desktop Services:: D-Bus and desktop services.
6138 * Database Services:: SQL databases.
6139 * Web Services:: Web servers.
6140 * Various Services:: Other services.
6144 @subsubsection Base Services
6146 The @code{(gnu services base)} module provides definitions for the basic
6147 services that one expects from the system. The services exported by
6148 this module are listed below.
6150 @defvr {Scheme Variable} %base-services
6151 This variable contains a list of basic services@footnote{Technically,
6152 this is a list of monadic services. @xref{The Store Monad}.} one would
6153 expect from the system: a login service (mingetty) on each tty, syslogd,
6154 libc's name service cache daemon (nscd), the udev device manager, and
6157 This is the default value of the @code{services} field of
6158 @code{operating-system} declarations. Usually, when customizing a
6159 system, you will want to append services to @var{%base-services}, like
6163 (cons* (avahi-service) (lsh-service) %base-services)
6167 @deffn {Scheme Procedure} host-name-service @var{name}
6168 Return a service that sets the host name to @var{name}.
6171 @deffn {Scheme Procedure} mingetty-service @var{config}
6172 Return a service to run mingetty according to @var{config}, a
6173 @code{<mingetty-configuration>} object, which specifies the tty to run, among
6177 @deftp {Data Type} mingetty-configuration
6178 This is the data type representing the configuration of Mingetty, which
6179 implements console log-in.
6184 The name of the console this Mingetty runs on---e.g., @code{"tty1"}.
6187 A file-like object containing the ``message of the day''.
6189 @item @code{auto-login} (default: @code{#f})
6190 When true, this field must be a string denoting the user name under
6191 which the the system automatically logs in. When it is @code{#f}, a
6192 user name and password must be entered to log in.
6194 @item @code{login-program} (default: @code{#f})
6195 This must be either @code{#f}, in which case the default log-in program
6196 is used (@command{login} from the Shadow tool suite), or a gexp denoting
6197 the name of the log-in program.
6199 @item @code{login-pause?} (default: @code{#f})
6200 When set to @code{#t} in conjunction with @var{auto-login}, the user
6201 will have to press a key before the log-in shell is launched.
6203 @item @code{mingetty} (default: @var{mingetty})
6204 The Mingetty package to use.
6209 @cindex name service cache daemon
6211 @deffn {Scheme Procedure} nscd-service [@var{config}] [#:glibc glibc] @
6212 [#:name-services '()]
6213 Return a service that runs libc's name service cache daemon (nscd) with the
6214 given @var{config}---an @code{<nscd-configuration>} object. @xref{Name
6215 Service Switch}, for an example.
6218 @defvr {Scheme Variable} %nscd-default-configuration
6219 This is the default @code{<nscd-configuration>} value (see below) used
6220 by @code{nscd-service}. This uses the caches defined by
6221 @var{%nscd-default-caches}; see below.
6224 @deftp {Data Type} nscd-configuration
6225 This is the type representing the name service cache daemon (nscd)
6230 @item @code{name-services} (default: @code{'()})
6231 List of packages denoting @dfn{name services} that must be visible to
6232 the nscd---e.g., @code{(list @var{nss-mdns})}.
6234 @item @code{glibc} (default: @var{glibc})
6235 Package object denoting the GNU C Library providing the @command{nscd}
6238 @item @code{log-file} (default: @code{"/var/log/nscd.log"})
6239 Name of nscd's log file. This is where debugging output goes when
6240 @code{debug-level} is strictly positive.
6242 @item @code{debug-level} (default: @code{0})
6243 Integer denoting the debugging levels. Higher numbers mean more
6244 debugging output is logged.
6246 @item @code{caches} (default: @var{%nscd-default-caches})
6247 List of @code{<nscd-cache>} objects denoting things to be cached; see
6253 @deftp {Data Type} nscd-cache
6254 Data type representing a cache database of nscd and its parameters.
6258 @item @code{database}
6259 This is a symbol representing the name of the database to be cached.
6260 Valid values are @code{passwd}, @code{group}, @code{hosts}, and
6261 @code{services}, which designate the corresponding NSS database
6262 (@pxref{NSS Basics,,, libc, The GNU C Library Reference Manual}).
6264 @item @code{positive-time-to-live}
6265 @itemx @code{negative-time-to-live} (default: @code{20})
6266 A number representing the number of seconds during which a positive or
6267 negative lookup result remains in cache.
6269 @item @code{check-files?} (default: @code{#t})
6270 Whether to check for updates of the files corresponding to
6273 For instance, when @var{database} is @code{hosts}, setting this flag
6274 instructs nscd to check for updates in @file{/etc/hosts} and to take
6277 @item @code{persistent?} (default: @code{#t})
6278 Whether the cache should be stored persistently on disk.
6280 @item @code{shared?} (default: @code{#t})
6281 Whether the cache should be shared among users.
6283 @item @code{max-database-size} (default: 32@tie{}MiB)
6284 Maximum size in bytes of the database cache.
6286 @c XXX: 'suggested-size' and 'auto-propagate?' seem to be expert
6287 @c settings, so leave them out.
6292 @defvr {Scheme Variable} %nscd-default-caches
6293 List of @code{<nscd-cache>} objects used by default by
6294 @code{nscd-configuration} (see above.)
6296 It enables persistent and aggressive caching of service and host name
6297 lookups. The latter provides better host name lookup performance,
6298 resilience in the face of unreliable name servers, and also better
6299 privacy---often the result of host name lookups is in local cache, so
6300 external name servers do not even need to be queried.
6304 @deffn {Scheme Procedure} syslog-service [#:config-file #f]
6305 Return a service that runs @code{syslogd}. If configuration file name
6306 @var{config-file} is not specified, use some reasonable default
6310 @anchor{guix-configuration-type}
6311 @deftp {Data Type} guix-configuration
6312 This data type represents the configuration of the Guix build daemon.
6313 @xref{Invoking guix-daemon}, for more information.
6316 @item @code{guix} (default: @var{guix})
6317 The Guix package to use.
6319 @item @code{build-group} (default: @code{"guixbuild"})
6320 Name of the group for build user accounts.
6322 @item @code{build-accounts} (default: @code{10})
6323 Number of build user accounts to create.
6325 @item @code{authorize-key?} (default: @code{#t})
6326 Whether to authorize the substitute key for @code{hydra.gnu.org}
6327 (@pxref{Substitutes}).
6329 @item @code{use-substitutes?} (default: @code{#t})
6330 Whether to use substitutes.
6332 @item @code{substitute-urls} (default: @var{%default-substitute-urls})
6333 The list of URLs where to look for substitutes by default.
6335 @item @code{extra-options} (default: @code{'()})
6336 List of extra command-line options for @command{guix-daemon}.
6338 @item @code{lsof} (default: @var{lsof})
6339 @itemx @code{lsh} (default: @var{lsh})
6340 The lsof and lsh packages to use.
6345 @deffn {Scheme Procedure} guix-service @var{config}
6346 Return a service that runs the Guix build daemon according to
6350 @deffn {Scheme Procedure} udev-service [#:udev udev]
6351 Run @var{udev}, which populates the @file{/dev} directory dynamically.
6354 @deffn {Scheme Procedure} console-keymap-service @var{file}
6355 Return a service to load console keymap from @var{file} using
6356 @command{loadkeys} command.
6360 @node Networking Services
6361 @subsubsection Networking Services
6363 The @code{(gnu services networking)} module provides services to configure
6364 the network interface.
6366 @cindex DHCP, networking service
6367 @deffn {Scheme Procedure} dhcp-client-service [#:dhcp @var{isc-dhcp}]
6368 Return a service that runs @var{dhcp}, a Dynamic Host Configuration
6369 Protocol (DHCP) client, on all the non-loopback network interfaces.
6372 @deffn {Scheme Procedure} static-networking-service @var{interface} @var{ip} @
6373 [#:gateway #f] [#:name-services @code{'()}]
6374 Return a service that starts @var{interface} with address @var{ip}. If
6375 @var{gateway} is true, it must be a string specifying the default network
6380 @deffn {Scheme Procedure} wicd-service [#:wicd @var{wicd}]
6381 Return a service that runs @url{https://launchpad.net/wicd,Wicd}, a
6382 network manager that aims to simplify wired and wireless networking.
6385 @deffn {Scheme Procedure} ntp-service [#:ntp @var{ntp}] @
6386 [#:name-service @var{%ntp-servers}]
6387 Return a service that runs the daemon from @var{ntp}, the
6388 @uref{http://www.ntp.org, Network Time Protocol package}. The daemon will
6389 keep the system clock synchronized with that of @var{servers}.
6392 @defvr {Scheme Variable} %ntp-servers
6393 List of host names used as the default NTP servers.
6396 @deffn {Scheme Procedure} tor-service [@var{config-file}] [#:tor @var{tor}]
6397 Return a service to run the @uref{https://torproject.org, Tor} anonymous
6400 The daemon runs as the @code{tor} unprivileged user. It is passed
6401 @var{config-file}, a file-like object, with an additional @code{User tor}
6402 line. Run @command{man tor} for information about the configuration file.
6405 @deffn {Scheme Procedure} bitlbee-service [#:bitlbee bitlbee] @
6406 [#:interface "127.0.0.1"] [#:port 6667] @
6407 [#:extra-settings ""]
6408 Return a service that runs @url{http://bitlbee.org,BitlBee}, a daemon that
6409 acts as a gateway between IRC and chat networks.
6411 The daemon will listen to the interface corresponding to the IP address
6412 specified in @var{interface}, on @var{port}. @code{127.0.0.1} means that only
6413 local clients can connect, whereas @code{0.0.0.0} means that connections can
6414 come from any networking interface.
6416 In addition, @var{extra-settings} specifies a string to append to the
6420 Furthermore, @code{(gnu services ssh)} provides the following service.
6422 @deffn {Scheme Procedure} lsh-service [#:host-key "/etc/lsh/host-key"] @
6423 [#:daemonic? #t] [#:interfaces '()] [#:port-number 22] @
6424 [#:allow-empty-passwords? #f] [#:root-login? #f] @
6425 [#:syslog-output? #t] [#:x11-forwarding? #t] @
6426 [#:tcp/ip-forwarding? #t] [#:password-authentication? #t] @
6427 [#:public-key-authentication? #t] [#:initialize? #t]
6428 Run the @command{lshd} program from @var{lsh} to listen on port @var{port-number}.
6429 @var{host-key} must designate a file containing the host key, and readable
6432 When @var{daemonic?} is true, @command{lshd} will detach from the
6433 controlling terminal and log its output to syslogd, unless one sets
6434 @var{syslog-output?} to false. Obviously, it also makes lsh-service
6435 depend on existence of syslogd service. When @var{pid-file?} is true,
6436 @command{lshd} writes its PID to the file called @var{pid-file}.
6438 When @var{initialize?} is true, automatically create the seed and host key
6439 upon service activation if they do not exist yet. This may take long and
6440 require interaction.
6442 When @var{initialize?} is false, it is up to the user to initialize the
6443 randomness generator (@pxref{lsh-make-seed,,, lsh, LSH Manual}), and to create
6444 a key pair with the private key stored in file @var{host-key} (@pxref{lshd
6445 basics,,, lsh, LSH Manual}).
6447 When @var{interfaces} is empty, lshd listens for connections on all the
6448 network interfaces; otherwise, @var{interfaces} must be a list of host names
6451 @var{allow-empty-passwords?} specifies whether to accept log-ins with empty
6452 passwords, and @var{root-login?} specifies whether to accept log-ins as
6455 The other options should be self-descriptive.
6458 @defvr {Scheme Variable} %facebook-host-aliases
6459 This variable contains a string for use in @file{/etc/hosts}
6460 (@pxref{Host Names,,, libc, The GNU C Library Reference Manual}). Each
6461 line contains a entry that maps a known server name of the Facebook
6462 on-line service---e.g., @code{www.facebook.com}---to the local
6463 host---@code{127.0.0.1} or its IPv6 equivalent, @code{::1}.
6465 This variable is typically used in the @code{hosts-file} field of an
6466 @code{operating-system} declaration (@pxref{operating-system Reference,
6467 @file{/etc/hosts}}):
6470 (use-modules (gnu) (guix))
6473 (host-name "mymachine")
6476 ;; Create a /etc/hosts file with aliases for "localhost"
6477 ;; and "mymachine", as well as for Facebook servers.
6479 (string-append (local-host-aliases host-name)
6480 %facebook-host-aliases))))
6483 This mechanism can prevent programs running locally, such as Web
6484 browsers, from accessing Facebook.
6487 The @code{(gnu services avahi)} provides the following definition.
6489 @deffn {Scheme Procedure} avahi-service [#:avahi @var{avahi}] @
6490 [#:host-name #f] [#:publish? #t] [#:ipv4? #t] @
6491 [#:ipv6? #t] [#:wide-area? #f] @
6492 [#:domains-to-browse '()]
6493 Return a service that runs @command{avahi-daemon}, a system-wide
6494 mDNS/DNS-SD responder that allows for service discovery and
6495 "zero-configuration" host name lookups (see @uref{http://avahi.org/}), and
6496 extends the name service cache daemon (nscd) so that it can resolve
6497 @code{.local} host names using
6498 @uref{http://0pointer.de/lennart/projects/nss-mdns/, nss-mdns}.
6500 If @var{host-name} is different from @code{#f}, use that as the host name to
6501 publish for this machine; otherwise, use the machine's actual host name.
6503 When @var{publish?} is true, publishing of host names and services is allowed;
6504 in particular, avahi-daemon will publish the machine's host name and IP
6505 address via mDNS on the local network.
6507 When @var{wide-area?} is true, DNS-SD over unicast DNS is enabled.
6509 Boolean values @var{ipv4?} and @var{ipv6?} determine whether to use IPv4/IPv6
6515 @subsubsection X Window
6517 Support for the X Window graphical display system---specifically
6518 Xorg---is provided by the @code{(gnu services xorg)} module. Note that
6519 there is no @code{xorg-service} procedure. Instead, the X server is
6520 started by the @dfn{login manager}, currently SLiM.
6522 @deffn {Scheme Procedure} slim-service [#:allow-empty-passwords? #f] @
6523 [#:auto-login? #f] [#:default-user ""] [#:startx] @
6524 [#:theme @var{%default-slim-theme}] @
6525 [#:theme-name @var{%default-slim-theme-name}]
6526 Return a service that spawns the SLiM graphical login manager, which in
6527 turn starts the X display server with @var{startx}, a command as returned by
6528 @code{xorg-start-command}.
6532 SLiM automatically looks for session types described by the @file{.desktop}
6533 files in @file{/run/current-system/profile/share/xsessions} and allows users
6534 to choose a session from the log-in screen using @kbd{F1}. Packages such as
6535 @var{xfce}, @var{sawfish}, and @var{ratpoison} provide @file{.desktop} files;
6536 adding them to the system-wide set of packages automatically makes them
6537 available at the log-in screen.
6539 In addition, @file{~/.xsession} files are honored. When available,
6540 @file{~/.xsession} must be an executable that starts a window manager
6541 and/or other X clients.
6543 When @var{allow-empty-passwords?} is true, allow logins with an empty
6544 password. When @var{auto-login?} is true, log in automatically as
6547 If @var{theme} is @code{#f}, the use the default log-in theme; otherwise
6548 @var{theme} must be a gexp denoting the name of a directory containing the
6549 theme to use. In that case, @var{theme-name} specifies the name of the
6553 @defvr {Scheme Variable} %default-theme
6554 @defvrx {Scheme Variable} %default-theme-name
6555 The G-Expression denoting the default SLiM theme and its name.
6558 @deffn {Scheme Procedure} xorg-start-command [#:guile] @
6559 [#:configuration-file #f] [#:xorg-server @var{xorg-server}]
6560 Return a derivation that builds a @var{guile} script to start the X server
6561 from @var{xorg-server}. @var{configuration-file} is the server configuration
6562 file or a derivation that builds it; when omitted, the result of
6563 @code{xorg-configuration-file} is used.
6565 Usually the X server is started by a login manager.
6568 @deffn {Scheme Procedure} xorg-configuration-file @
6569 [#:drivers '()] [#:resolutions '()] [#:extra-config '()]
6570 Return a configuration file for the Xorg server containing search paths for
6571 all the common drivers.
6573 @var{drivers} must be either the empty list, in which case Xorg chooses a
6574 graphics driver automatically, or a list of driver names that will be tried in
6575 this order---e.g., @code{(\"modesetting\" \"vesa\")}.
6577 Likewise, when @var{resolutions} is the empty list, Xorg chooses an
6578 appropriate screen resolution; otherwise, it must be a list of
6579 resolutions---e.g., @code{((1024 768) (640 480))}.
6581 Last, @var{extra-config} is a list of strings or objects appended to the
6582 @code{text-file*} argument list. It is used to pass extra text to be added
6583 verbatim to the configuration file.
6586 @deffn {Scheme Procedure} screen-locker-service @var{package} [@var{name}]
6587 Add @var{package}, a package for a screen-locker or screen-saver whose
6588 command is @var{program}, to the set of setuid programs and add a PAM entry
6589 for it. For example:
6592 (screen-locker-service xlockmore "xlock")
6595 makes the good ol' XlockMore usable.
6599 @node Desktop Services
6600 @subsubsection Desktop Services
6602 The @code{(gnu services desktop)} module provides services that are
6603 usually useful in the context of a ``desktop'' setup---that is, on a
6604 machine running a graphical display server, possibly with graphical user
6607 To simplify things, the module defines a variable containing the set of
6608 services that users typically expect on a machine with a graphical
6609 environment and networking:
6611 @defvr {Scheme Variable} %desktop-services
6612 This is a list of services that builds upon @var{%base-services} and
6613 adds or adjust services for a typical ``desktop'' setup.
6615 In particular, it adds a graphical login manager (@pxref{X Window,
6616 @code{slim-service}}), screen lockers,
6617 a network management tool (@pxref{Networking
6618 Services, @code{wicd-service}}), energy and color management services,
6619 the @code{elogind} login and seat manager, the Polkit privilege service,
6620 the GeoClue location service, an NTP client (@pxref{Networking
6621 Services}), the Avahi daemon, and has the name service switch service
6622 configured to be able to use @code{nss-mdns} (@pxref{Name Service
6626 The @var{%desktop-services} variable can be used as the @code{services}
6627 field of an @code{operating-system} declaration (@pxref{operating-system
6628 Reference, @code{services}}).
6630 The actual service definitions provided by @code{(gnu services dbus)}
6631 and @code{(gnu services desktop)} are described below.
6633 @deffn {Scheme Procedure} dbus-service [#:dbus @var{dbus}] [#:services '()]
6634 Return a service that runs the ``system bus'', using @var{dbus}, with
6635 support for @var{services}.
6637 @uref{http://dbus.freedesktop.org/, D-Bus} is an inter-process communication
6638 facility. Its system bus is used to allow system services to communicate
6639 and be notified of system-wide events.
6641 @var{services} must be a list of packages that provide an
6642 @file{etc/dbus-1/system.d} directory containing additional D-Bus configuration
6643 and policy files. For example, to allow avahi-daemon to use the system bus,
6644 @var{services} must be equal to @code{(list avahi)}.
6647 @deffn {Scheme Procedure} elogind-service [#:config @var{config}]
6648 Return a service that runs the @code{elogind} login and
6649 seat management daemon. @uref{https://github.com/andywingo/elogind,
6650 Elogind} exposes a D-Bus interface that can be used to know which users
6651 are logged in, know what kind of sessions they have open, suspend the
6652 system, inhibit system suspend, reboot the system, and other tasks.
6654 Elogind handles most system-level power events for a computer, for
6655 example suspending the system when a lid is closed, or shutting it down
6656 when the power button is pressed.
6658 The @var{config} keyword argument specifies the configuration for
6659 elogind, and should be the result of a @code{(elogind-configuration
6660 (@var{parameter} @var{value})...)} invocation. Available parameters and
6661 their default values are:
6664 @item kill-user-processes?
6666 @item kill-only-users
6668 @item kill-exclude-users
6670 @item inhibit-delay-max-seconds
6672 @item handle-power-key
6674 @item handle-suspend-key
6676 @item handle-hibernate-key
6678 @item handle-lid-switch
6680 @item handle-lid-switch-docked
6682 @item power-key-ignore-inhibited?
6684 @item suspend-key-ignore-inhibited?
6686 @item hibernate-key-ignore-inhibited?
6688 @item lid-switch-ignore-inhibited?
6690 @item holdoff-timeout-seconds
6694 @item idle-action-seconds
6696 @item runtime-directory-size-percent
6698 @item runtime-directory-size
6703 @code{("mem" "standby" "freeze")}
6706 @item hibernate-state
6708 @item hibernate-mode
6709 @code{("platform" "shutdown")}
6710 @item hybrid-sleep-state
6712 @item hybrid-sleep-mode
6713 @code{("suspend" "platform" "shutdown")}
6717 @deffn {Scheme Procedure} polkit-service @
6718 [#:polkit @var{polkit}]
6719 Return a service that runs the Polkit privilege manager.
6720 @uref{http://www.freedesktop.org/wiki/Software/polkit/, Polkit} allows
6721 system administrators to grant access to privileged operations in a
6722 structured way. For example, polkit rules can allow a logged-in user
6723 whose session is active to shut down the machine, if there are no other
6727 @deffn {Scheme Procedure} upower-service [#:upower @var{upower}] @
6728 [#:watts-up-pro? #f] @
6729 [#:poll-batteries? #t] @
6730 [#:ignore-lid? #f] @
6731 [#:use-percentage-for-policy? #f] @
6732 [#:percentage-low 10] @
6733 [#:percentage-critical 3] @
6734 [#:percentage-action 2] @
6736 [#:time-critical 300] @
6737 [#:time-action 120] @
6738 [#:critical-power-action 'hybrid-sleep]
6739 Return a service that runs @uref{http://upower.freedesktop.org/,
6740 @command{upowerd}}, a system-wide monitor for power consumption and battery
6741 levels, with the given configuration settings. It implements the
6742 @code{org.freedesktop.UPower} D-Bus interface, and is notably used by
6746 @deffn {Scheme Procedure} colord-service [#:colord @var{colord}]
6747 Return a service that runs @command{colord}, a system service with a D-Bus
6748 interface to manage the color profiles of input and output devices such as
6749 screens and scanners. It is notably used by the GNOME Color Manager graphical
6750 tool. See @uref{http://www.freedesktop.org/software/colord/, the colord web
6751 site} for more information.
6754 @deffn {Scheme Procedure} geoclue-application name [#:allowed? #t] [#:system? #f] [#:users '()]
6755 Return an configuration allowing an application to access GeoClue
6756 location data. @var{name} is the Desktop ID of the application, without
6757 the @code{.desktop} part. If @var{allowed?} is true, the application
6758 will have access to location information by default. The boolean
6759 @var{system?} value indicates that an application is a system component
6760 or not. Finally @var{users} is a list of UIDs of all users for which
6761 this application is allowed location info access. An empty users list
6762 means that all users are allowed.
6765 @defvr {Scheme Variable} %standard-geoclue-applications
6766 The standard list of well-known GeoClue application configurations,
6767 granting authority to GNOME's date-and-time utility to ask for the
6768 current location in order to set the time zone, and allowing the Firefox
6769 (IceCat) and Epiphany web browsers to request location information.
6770 Firefox and Epiphany both query the user before allowing a web page to
6771 know the user's location.
6774 @deffn {Scheme Procedure} geoclue-service [#:colord @var{colord}] @
6776 [#:wifi-geolocation-url "https://location.services.mozilla.com/v1/geolocate?key=geoclue"] @
6778 [#:wifi-submission-url "https://location.services.mozilla.com/v1/submit?key=geoclue"] @
6779 [#:submission-nick "geoclue"] @
6780 [#:applications %standard-geoclue-applications]
6781 Return a service that runs the GeoClue location service. This service
6782 provides a D-Bus interface to allow applications to request access to a
6783 user's physical location, and optionally to add information to online
6784 location databases. See
6785 @uref{https://wiki.freedesktop.org/www/Software/GeoClue/, the GeoClue
6786 web site} for more information.
6789 @node Database Services
6790 @subsubsection Database Services
6792 The @code{(gnu services databases)} module provides the following service.
6794 @deffn {Scheme Procedure} postgresql-service [#:postgresql postgresql] @
6795 [#:config-file] [#:data-directory ``/var/lib/postgresql/data'']
6796 Return a service that runs @var{postgresql}, the PostgreSQL database
6799 The PostgreSQL daemon loads its runtime configuration from
6800 @var{config-file} and stores the database cluster in
6801 @var{data-directory}.
6805 @subsubsection Web Services
6807 The @code{(gnu services web)} module provides the following service:
6809 @deffn {Scheme Procedure} nginx-service [#:nginx nginx] @
6810 [#:log-directory ``/var/log/nginx''] @
6811 [#:run-directory ``/var/run/nginx''] @
6814 Return a service that runs @var{nginx}, the nginx web server.
6816 The nginx daemon loads its runtime configuration from @var{config-file}.
6817 Log files are written to @var{log-directory} and temporary runtime data
6818 files are written to @var{run-directory}. For proper operation, these
6819 arguments should match what is in @var{config-file} to ensure that the
6820 directories are created when the service is activated.
6824 @node Various Services
6825 @subsubsection Various Services
6827 The @code{(gnu services lirc)} module provides the following service.
6829 @deffn {Scheme Procedure} lirc-service [#:lirc lirc] @
6830 [#:device #f] [#:driver #f] [#:config-file #f] @
6831 [#:extra-options '()]
6832 Return a service that runs @url{http://www.lirc.org,LIRC}, a daemon that
6833 decodes infrared signals from remote controls.
6835 Optionally, @var{device}, @var{driver} and @var{config-file}
6836 (configuration file name) may be specified. See @command{lircd} manual
6839 Finally, @var{extra-options} is a list of additional command-line options
6840 passed to @command{lircd}.
6844 @node Setuid Programs
6845 @subsection Setuid Programs
6847 @cindex setuid programs
6848 Some programs need to run with ``root'' privileges, even when they are
6849 launched by unprivileged users. A notorious example is the
6850 @command{passwd} program, which users can run to change their
6851 password, and which needs to access the @file{/etc/passwd} and
6852 @file{/etc/shadow} files---something normally restricted to root, for
6853 obvious security reasons. To address that, these executables are
6854 @dfn{setuid-root}, meaning that they always run with root privileges
6855 (@pxref{How Change Persona,,, libc, The GNU C Library Reference Manual},
6856 for more info about the setuid mechanisms.)
6858 The store itself @emph{cannot} contain setuid programs: that would be a
6859 security issue since any user on the system can write derivations that
6860 populate the store (@pxref{The Store}). Thus, a different mechanism is
6861 used: instead of changing the setuid bit directly on files that are in
6862 the store, we let the system administrator @emph{declare} which programs
6863 should be setuid root.
6865 The @code{setuid-programs} field of an @code{operating-system}
6866 declaration contains a list of G-expressions denoting the names of
6867 programs to be setuid-root (@pxref{Using the Configuration System}).
6868 For instance, the @command{passwd} program, which is part of the Shadow
6869 package, can be designated by this G-expression (@pxref{G-Expressions}):
6872 #~(string-append #$shadow "/bin/passwd")
6875 A default set of setuid programs is defined by the
6876 @code{%setuid-programs} variable of the @code{(gnu system)} module.
6878 @defvr {Scheme Variable} %setuid-programs
6879 A list of G-expressions denoting common programs that are setuid-root.
6881 The list includes commands such as @command{passwd}, @command{ping},
6882 @command{su}, and @command{sudo}.
6885 Under the hood, the actual setuid programs are created in the
6886 @file{/run/setuid-programs} directory at system activation time. The
6887 files in this directory refer to the ``real'' binaries, which are in the
6890 @node X.509 Certificates
6891 @subsection X.509 Certificates
6893 @cindex HTTPS, certificates
6894 @cindex X.509 certificates
6896 Web servers available over HTTPS (that is, HTTP over the transport-layer
6897 security mechanism, TLS) send client programs an @dfn{X.509 certificate}
6898 that the client can then use to @emph{authenticate} the server. To do
6899 that, clients verify that the server's certificate is signed by a
6900 so-called @dfn{certificate authority} (CA). But to verify the CA's
6901 signature, clients must have first acquired the CA's certificate.
6903 Web browsers such as GNU@tie{}IceCat include their own set of CA
6904 certificates, such that they are able to verify CA signatures
6907 However, most other programs that can talk HTTPS---@command{wget},
6908 @command{git}, @command{w3m}, etc.---need to be told where CA
6909 certificates can be found.
6911 @cindex @code{nss-certs}
6912 In GuixSD, this is done by adding a package that provides certificates
6913 to the @code{packages} field of the @code{operating-system} declaration
6914 (@pxref{operating-system Reference}). GuixSD includes one such package,
6915 @code{nss-certs}, which is a set of CA certificates provided as part of
6916 Mozilla's Network Security Services.
6918 Note that it is @emph{not} part of @var{%base-packages}, so you need to
6919 explicitly add it. The @file{/etc/ssl/certs} directory, which is where
6920 most applications and libraries look for certificates by default, points
6921 to the certificates installed globally.
6923 Unprivileged users can also install their own certificate package in
6924 their profile. A number of environment variables need to be defined so
6925 that applications and libraries know where to find them. Namely, the
6926 OpenSSL library honors the @code{SSL_CERT_DIR} and @code{SSL_CERT_FILE}
6927 variables. Some applications add their own environment variables; for
6928 instance, the Git version control system honors the certificate bundle
6929 pointed to by the @code{GIT_SSL_CAINFO} environment variable.
6932 @node Name Service Switch
6933 @subsection Name Service Switch
6935 @cindex name service switch
6937 The @code{(gnu system nss)} module provides bindings to the
6938 configuration file of libc's @dfn{name service switch} or @dfn{NSS}
6939 (@pxref{NSS Configuration File,,, libc, The GNU C Library Reference
6940 Manual}). In a nutshell, the NSS is a mechanism that allows libc to be
6941 extended with new ``name'' lookup methods for system databases, which
6942 includes host names, service names, user accounts, and more (@pxref{Name
6943 Service Switch, System Databases and Name Service Switch,, libc, The GNU
6944 C Library Reference Manual}).
6946 The NSS configuration specifies, for each system database, which lookup
6947 method is to be used, and how the various methods are chained
6948 together---for instance, under which circumstances NSS should try the
6949 next method in the list. The NSS configuration is given in the
6950 @code{name-service-switch} field of @code{operating-system} declarations
6951 (@pxref{operating-system Reference, @code{name-service-switch}}).
6954 @cindex .local, host name lookup
6955 As an example, the declaration below configures the NSS to use the
6956 @uref{http://0pointer.de/lennart/projects/nss-mdns/, @code{nss-mdns}
6957 back-end}, which supports host name lookups over multicast DNS (mDNS)
6958 for host names ending in @code{.local}:
6961 (name-service-switch
6962 (hosts (list %files ;first, check /etc/hosts
6964 ;; If the above did not succeed, try
6965 ;; with 'mdns_minimal'.
6967 (name "mdns_minimal")
6969 ;; 'mdns_minimal' is authoritative for
6970 ;; '.local'. When it returns "not found",
6971 ;; no need to try the next methods.
6972 (reaction (lookup-specification
6973 (not-found => return))))
6975 ;; Then fall back to DNS.
6979 ;; Finally, try with the "full" 'mdns'.
6984 Don't worry: the @code{%mdns-host-lookup-nss} variable (see below)
6985 contains this configuration, so you won't have to type it if all you
6986 want is to have @code{.local} host lookup working.
6988 Note that, in this case, in addition to setting the
6989 @code{name-service-switch} of the @code{operating-system} declaration,
6990 you also need to use @code{avahi-service} (@pxref{Networking Services,
6991 @code{avahi-service}}), or @var{%desktop-services}, which includes it
6992 (@pxref{Desktop Services}). Doing this makes @code{nss-mdns} accessible
6993 to the name service cache daemon (@pxref{Base Services,
6994 @code{nscd-service}}).
6996 For convenience, the following variables provide typical NSS
6999 @defvr {Scheme Variable} %default-nss
7000 This is the default name service switch configuration, a
7001 @code{name-service-switch} object.
7004 @defvr {Scheme Variable} %mdns-host-lookup-nss
7005 This is the name service switch configuration with support for host name
7006 lookup over multicast DNS (mDNS) for host names ending in @code{.local}.
7009 The reference for name service switch configuration is given below. It
7010 is a direct mapping of the C library's configuration file format, so
7011 please refer to the C library manual for more information (@pxref{NSS
7012 Configuration File,,, libc, The GNU C Library Reference Manual}).
7013 Compared to libc's NSS configuration file format, it has the advantage
7014 not only of adding this warm parenthetic feel that we like, but also
7015 static checks: you'll know about syntax errors and typos as soon as you
7016 run @command{guix system}.
7018 @deftp {Data Type} name-service-switch
7020 This is the data type representation the configuration of libc's name
7021 service switch (NSS). Each field below represents one of the supported
7038 The system databases handled by the NSS. Each of these fields must be a
7039 list of @code{<name-service>} objects (see below.)
7043 @deftp {Data Type} name-service
7045 This is the data type representing an actual name service and the
7046 associated lookup action.
7050 A string denoting the name service (@pxref{Services in the NSS
7051 configuration,,, libc, The GNU C Library Reference Manual}).
7053 Note that name services listed here must be visible to nscd. This is
7054 achieved by passing the @code{#:name-services} argument to
7055 @code{nscd-service} the list of packages providing the needed name
7056 services (@pxref{Base Services, @code{nscd-service}}).
7059 An action specified using the @code{lookup-specification} macro
7060 (@pxref{Actions in the NSS configuration,,, libc, The GNU C Library
7061 Reference Manual}). For example:
7064 (lookup-specification (unavailable => continue)
7065 (success => return))
7070 @node Initial RAM Disk
7071 @subsection Initial RAM Disk
7073 @cindex initial RAM disk (initrd)
7074 @cindex initrd (initial RAM disk)
7075 For bootstrapping purposes, the Linux-Libre kernel is passed an
7076 @dfn{initial RAM disk}, or @dfn{initrd}. An initrd contains a temporary
7077 root file system, as well as an initialization script. The latter is
7078 responsible for mounting the real root file system, and for loading any
7079 kernel modules that may be needed to achieve that.
7081 The @code{initrd} field of an @code{operating-system} declaration allows
7082 you to specify which initrd you would like to use. The @code{(gnu
7083 system linux-initrd)} module provides two ways to build an initrd: the
7084 high-level @code{base-initrd} procedure, and the low-level
7085 @code{expression->initrd} procedure.
7087 The @code{base-initrd} procedure is intended to cover most common uses.
7088 For example, if you want to add a bunch of kernel modules to be loaded
7089 at boot time, you can define the @code{initrd} field of the operating
7090 system declaration like this:
7093 (initrd (lambda (file-systems . rest)
7094 ;; Create a standard initrd that has modules "foo.ko"
7095 ;; and "bar.ko", as well as their dependencies, in
7096 ;; addition to the modules available by default.
7097 (apply base-initrd file-systems
7098 #:extra-modules '("foo" "bar")
7102 The @code{base-initrd} procedure also handles common use cases that
7103 involves using the system as a QEMU guest, or as a ``live'' system whose
7104 root file system is volatile.
7106 @deffn {Monadic Procedure} base-initrd @var{file-systems} @
7107 [#:qemu-networking? #f] [#:virtio? #f] [#:volatile-root? #f] @
7108 [#:extra-modules '()] [#:mapped-devices '()]
7109 Return a monadic derivation that builds a generic initrd. @var{file-systems} is
7110 a list of file-systems to be mounted by the initrd, possibly in addition to
7111 the root file system specified on the kernel command line via @code{--root}.
7112 @var{mapped-devices} is a list of device mappings to realize before
7113 @var{file-systems} are mounted (@pxref{Mapped Devices}).
7115 When @var{qemu-networking?} is true, set up networking with the standard QEMU
7116 parameters. When @var{virtio?} is true, load additional modules so the initrd can
7117 be used as a QEMU guest with para-virtualized I/O drivers.
7119 When @var{volatile-root?} is true, the root file system is writable but any changes
7122 The initrd is automatically populated with all the kernel modules necessary
7123 for @var{file-systems} and for the given options. However, additional kernel
7124 modules can be listed in @var{extra-modules}. They will be added to the initrd, and
7125 loaded at boot time in the order in which they appear.
7128 Needless to say, the initrds we produce and use embed a
7129 statically-linked Guile, and the initialization program is a Guile
7130 program. That gives a lot of flexibility. The
7131 @code{expression->initrd} procedure builds such an initrd, given the
7132 program to run in that initrd.
7134 @deffn {Monadic Procedure} expression->initrd @var{exp} @
7135 [#:guile %guile-static-stripped] [#:name "guile-initrd"] @
7137 Return a derivation that builds a Linux initrd (a gzipped cpio archive)
7138 containing @var{guile} and that evaluates @var{exp}, a G-expression,
7139 upon booting. All the derivations referenced by @var{exp} are
7140 automatically copied to the initrd.
7142 @var{modules} is a list of Guile module names to be embedded in the
7146 @node GRUB Configuration
7147 @subsection GRUB Configuration
7152 The operating system uses GNU@tie{}GRUB as its boot loader
7153 (@pxref{Overview, overview of GRUB,, grub, GNU GRUB Manual}). It is
7154 configured using @code{grub-configuration} declarations. This data type
7155 is exported by the @code{(gnu system grub)} module, and described below.
7157 @deftp {Data Type} grub-configuration
7158 The type of a GRUB configuration declaration.
7163 This is a string denoting the boot device. It must be a device name
7164 understood by the @command{grub-install} command, such as
7165 @code{/dev/sda} or @code{(hd0)} (@pxref{Invoking grub-install,,, grub,
7168 @item @code{menu-entries} (default: @code{()})
7169 A possibly empty list of @code{menu-entry} objects (see below), denoting
7170 entries to appear in the GRUB boot menu, in addition to the current
7171 system entry and the entry pointing to previous system generations.
7173 @item @code{default-entry} (default: @code{0})
7174 The index of the default boot menu entry. Index 0 is for the current
7177 @item @code{timeout} (default: @code{5})
7178 The number of seconds to wait for keyboard input before booting. Set to
7179 0 to boot immediately, and to -1 to wait indefinitely.
7181 @item @code{theme} (default: @var{%default-theme})
7182 The @code{grub-theme} object describing the theme to use.
7187 Should you want to list additional boot menu entries @i{via} the
7188 @code{menu-entries} field above, you will need to create them with the
7189 @code{menu-entry} form:
7191 @deftp {Data Type} menu-entry
7192 The type of an entry in the GRUB boot menu.
7197 The label to show in the menu---e.g., @code{"GNU"}.
7200 The Linux kernel to boot.
7202 @item @code{linux-arguments} (default: @code{()})
7203 The list of extra Linux kernel command-line arguments---e.g.,
7204 @code{("console=ttyS0")}.
7207 A G-Expression or string denoting the file name of the initial RAM disk
7208 to use (@pxref{G-Expressions}).
7213 @c FIXME: Write documentation once it's stable.
7214 Themes are created using the @code{grub-theme} form, which is not
7217 @defvr {Scheme Variable} %default-theme
7218 This is the default GRUB theme used by the operating system, with a
7219 fancy background image displaying the GNU and Guix logos.
7223 @node Invoking guix system
7224 @subsection Invoking @code{guix system}
7226 Once you have written an operating system declaration, as seen in the
7227 previous section, it can be @dfn{instantiated} using the @command{guix
7228 system} command. The synopsis is:
7231 guix system @var{options}@dots{} @var{action} @var{file}
7234 @var{file} must be the name of a file containing an
7235 @code{operating-system} declaration. @var{action} specifies how the
7236 operating system is instantiate. Currently the following values are
7241 Build the operating system described in @var{file}, activate it, and
7242 switch to it@footnote{This action is usable only on systems already
7245 This effects all the configuration specified in @var{file}: user
7246 accounts, system services, global package list, setuid programs, etc.
7248 It also adds a GRUB menu entry for the new OS configuration, and moves
7249 entries for older configurations to a submenu---unless
7250 @option{--no-grub} is passed.
7252 @c The paragraph below refers to the problem discussed at
7253 @c <http://lists.gnu.org/archive/html/guix-devel/2014-08/msg00057.html>.
7254 It is highly recommended to run @command{guix pull} once before you run
7255 @command{guix system reconfigure} for the first time (@pxref{Invoking
7256 guix pull}). Failing to do that you would see an older version of Guix
7257 once @command{reconfigure} has completed.
7260 Build the operating system's derivation, which includes all the
7261 configuration files and programs needed to boot and run the system.
7262 This action does not actually install anything.
7265 Populate the given directory with all the files necessary to run the
7266 operating system specified in @var{file}. This is useful for first-time
7267 installations of GuixSD. For instance:
7270 guix system init my-os-config.scm /mnt
7273 copies to @file{/mnt} all the store items required by the configuration
7274 specified in @file{my-os-config.scm}. This includes configuration
7275 files, packages, and so on. It also creates other essential files
7276 needed for the system to operate correctly---e.g., the @file{/etc},
7277 @file{/var}, and @file{/run} directories, and the @file{/bin/sh} file.
7279 This command also installs GRUB on the device specified in
7280 @file{my-os-config}, unless the @option{--no-grub} option was passed.
7283 @cindex virtual machine
7285 @anchor{guix system vm}
7286 Build a virtual machine that contain the operating system declared in
7287 @var{file}, and return a script to run that virtual machine (VM).
7288 Arguments given to the script are passed as is to QEMU.
7290 The VM shares its store with the host system.
7292 Additional file systems can be shared between the host and the VM using
7293 the @code{--share} and @code{--expose} command-line options: the former
7294 specifies a directory to be shared with write access, while the latter
7295 provides read-only access to the shared directory.
7297 The example below creates a VM in which the user's home directory is
7298 accessible read-only, and where the @file{/exchange} directory is a
7299 read-write mapping of the host's @file{$HOME/tmp}:
7302 guix system vm my-config.scm \
7303 --expose=$HOME --share=$HOME/tmp=/exchange
7306 On GNU/Linux, the default is to boot directly to the kernel; this has
7307 the advantage of requiring only a very tiny root disk image since the
7308 host's store can then be mounted.
7310 The @code{--full-boot} option forces a complete boot sequence, starting
7311 with the bootloader. This requires more disk space since a root image
7312 containing at least the kernel, initrd, and bootloader data files must
7313 be created. The @code{--image-size} option can be used to specify the
7318 Return a virtual machine or disk image of the operating system declared
7319 in @var{file} that stands alone. Use the @option{--image-size} option
7320 to specify the size of the image.
7322 When using @code{vm-image}, the returned image is in qcow2 format, which
7323 the QEMU emulator can efficiently use.
7325 When using @code{disk-image}, a raw disk image is produced; it can be
7326 copied as is to a USB stick, for instance. Assuming @code{/dev/sdc} is
7327 the device corresponding to a USB stick, one can copy the image on it
7328 using the following command:
7331 # dd if=$(guix system disk-image my-os.scm) of=/dev/sdc
7335 Return a script to run the operating system declared in @var{file}
7336 within a container. Containers are a set of lightweight isolation
7337 mechanisms provided by the kernel Linux-libre. Containers are
7338 substantially less resource-demanding than full virtual machines since
7339 the kernel, shared objects, and other resources can be shared with the
7340 host system; this also means they provide thinner isolation.
7342 Currently, the script must be run as root in order to support more than
7343 a single user and group. The container shares its store with the host
7346 As with the @code{vm} action (@pxref{guix system vm}), additional file
7347 systems to be shared between the host and container can be specified
7348 using the @option{--share} and @option{--expose} options:
7351 guix system container my-config.scm \
7352 --expose=$HOME --share=$HOME/tmp=/exchange
7357 @var{options} can contain any of the common build options provided by
7358 @command{guix build} (@pxref{Invoking guix build}). In addition,
7359 @var{options} can contain one of the following:
7362 @item --system=@var{system}
7363 @itemx -s @var{system}
7364 Attempt to build for @var{system} instead of the host's system type.
7365 This works as per @command{guix build} (@pxref{Invoking guix build}).
7369 Return the derivation file name of the given operating system without
7372 @item --image-size=@var{size}
7373 For the @code{vm-image} and @code{disk-image} actions, create an image
7374 of the given @var{size}. @var{size} may be a number of bytes, or it may
7375 include a unit as a suffix (@pxref{Block size, size specifications,,
7376 coreutils, GNU Coreutils}).
7378 @item --on-error=@var{strategy}
7379 Apply @var{strategy} when an error occurs when reading @var{file}.
7380 @var{strategy} may be one of the following:
7383 @item nothing-special
7384 Report the error concisely and exit. This is the default strategy.
7387 Likewise, but also display a backtrace.
7390 Report the error and enter Guile's debugger. From there, you can run
7391 commands such as @code{,bt} to get a backtrace, @code{,locals} to
7392 display local variable values, and more generally inspect the program's
7393 state. @xref{Debug Commands,,, guile, GNU Guile Reference Manual}, for
7394 a list of available debugging commands.
7398 Note that all the actions above, except @code{build} and @code{init},
7399 rely on KVM support in the Linux-Libre kernel. Specifically, the
7400 machine should have hardware virtualization support, the corresponding
7401 KVM kernel module should be loaded, and the @file{/dev/kvm} device node
7402 must exist and be readable and writable by the user and by the daemon's
7405 Once you have built, configured, re-configured, and re-re-configured
7406 your GuixSD installation, you may find it useful to list the operating
7407 system generations available on disk---and that you can choose from the
7412 @item list-generations
7413 List a summary of each generation of the operating system available on
7414 disk, in a human-readable way. This is similar to the
7415 @option{--list-generations} option of @command{guix package}
7416 (@pxref{Invoking guix package}).
7418 Optionally, one can specify a pattern, with the same syntax that is used
7419 in @command{guix package --list-generations}, to restrict the list of
7420 generations displayed. For instance, the following command displays
7421 generations up to 10-day old:
7424 $ guix system list-generations 10d
7429 The @command{guix system} command has even more to offer! The following
7430 sub-commands allow you to visualize how your system services relate to
7433 @anchor{system-extension-graph}
7436 @item extension-graph
7437 Emit in Dot/Graphviz format to standard output the @dfn{service
7438 extension graph} of the operating system defined in @var{file}
7439 (@pxref{Service Composition}, for more information on service
7445 $ guix system extension-graph @var{file} | dot -Tpdf > services.pdf
7448 produces a PDF file showing the extension relations among services.
7450 @anchor{system-dmd-graph}
7452 Emit in Dot/Graphviz format to standard output the @dfn{dependency
7453 graph} of dmd services of the operating system defined in @var{file}.
7454 @xref{dmd Services}, for more information and for an example graph.
7459 @node Defining Services
7460 @subsection Defining Services
7462 The previous sections show the available services and how one can combine
7463 them in an @code{operating-system} declaration. But how do we define
7464 them in the first place? And what is a service anyway?
7467 * Service Composition:: The model for composing services.
7468 * Service Types and Services:: Types and services.
7469 * Service Reference:: API reference.
7470 * dmd Services:: A particular type of service.
7473 @node Service Composition
7474 @subsubsection Service Composition
7478 Here we define a @dfn{service} as, broadly, something that extends the
7479 operating system's functionality. Often a service is a process---a
7480 @dfn{daemon}---started when the system boots: a secure shell server, a
7481 Web server, the Guix build daemon, etc. Sometimes a service is a daemon
7482 whose execution can be triggered by another daemon---e.g., an FTP server
7483 started by @command{inetd} or a D-Bus service activated by
7484 @command{dbus-daemon}. Occasionally, a service does not map to a
7485 daemon. For instance, the ``account'' service collects user accounts
7486 and makes sure they exist when the system runs; the ``udev'' service
7487 collects device management rules and makes them available to the eudev
7488 daemon; the @file{/etc} service populates the system's @file{/etc}
7491 @cindex service extensions
7492 GuixSD services are connected by @dfn{extensions}. For instance, the
7493 secure shell service @emph{extends} dmd---GuixSD's initialization system,
7494 running as PID@tie{}1---by giving it the command lines to start and stop
7495 the secure shell daemon (@pxref{Networking Services,
7496 @code{lsh-service}}); the UPower service extends the D-Bus service by
7497 passing it its @file{.service} specification, and extends the udev
7498 service by passing it device management rules (@pxref{Desktop Services,
7499 @code{upower-service}}); the Guix daemon service extends dmd by passing
7500 it the command lines to start and stop the daemon, and extends the
7501 account service by passing it a list of required build user accounts
7502 (@pxref{Base Services}).
7504 All in all, services and their ``extends'' relations form a directed
7505 acyclic graph (DAG). If we represent services as boxes and extensions
7506 as arrows, a typical system might provide something like this:
7508 @image{images/service-graph,,5in,Typical service extension graph.}
7510 At the bottom, we see the @dfn{boot service}, which produces the boot
7511 script that is executed at boot time from the initial RAM disk.
7512 @xref{system-extension-graph, the @command{guix system extension-graph}
7513 command}, for information on how to generate this representation for a
7514 particular operating system definition.
7516 @cindex service types
7517 Technically, developers can define @dfn{service types} to express these
7518 relations. There can be any number of services of a given type on the
7519 system---for instance, a system running two instances of the GNU secure
7520 shell server (lsh) has two instances of @var{lsh-service-type}, with
7521 different parameters.
7523 The following section describes the programming interface for service
7526 @node Service Types and Services
7527 @subsubsection Service Types and Services
7529 A @dfn{service type} is a node in the DAG described above. Let us start
7530 with a simple example, the service type for the Guix build daemon
7531 (@pxref{Invoking guix-daemon}):
7534 (define guix-service-type
7538 (list (service-extension dmd-root-service-type guix-dmd-service)
7539 (service-extension account-service-type guix-accounts)
7540 (service-extension activation-service-type guix-activation)))))
7544 It defines a two things:
7548 A name, whose sole purpose is to make inspection and debugging easier.
7551 A list of @dfn{service extensions}, where each extension designates the
7552 target service type and a procedure that, given the service's
7553 parameters, returns a list of object to extend the service of that type.
7555 Every service type has at least one service extension. The only
7556 exception is the @dfn{boot service type}, which is the ultimate service.
7559 In this example, @var{guix-service-type} extends three services:
7562 @item dmd-root-service-type
7563 The @var{guix-dmd-service} procedure defines how the dmd service is
7564 extended. Namely, it returns a @code{<dmd-service>} object that defines
7565 how @command{guix-daemon} is started and stopped (@pxref{dmd Services}).
7567 @item account-service-type
7568 This extension for this service is computed by @var{guix-accounts},
7569 which returns a list of @code{user-group} and @code{user-account}
7570 objects representing the build user accounts (@pxref{Invoking
7573 @item activation-service-type
7574 Here @var{guix-activation} is a procedure that returns a gexp, which is
7575 a code snippet to run at ``activation time''---e.g., when the service is
7579 A service of this type is instantiated like this:
7582 (service guix-service-type
7585 (use-substitutes? #f)))
7588 The second argument to the @code{service} form is a value representing
7589 the parameters of this specific service instance.
7590 @xref{guix-configuration-type, @code{guix-configuration}}, for
7591 information about the @code{guix-configuration} data type.
7593 @var{guix-service-type} is quite simple because it extends other
7594 services but is not extensible itself.
7596 @c @subsubsubsection Extensible Service Types
7598 The service type for an @emph{extensible} service looks like this:
7601 (define udev-service-type
7602 (service-type (name 'udev)
7604 (list (service-extension dmd-root-service-type
7607 (compose concatenate) ;concatenate the list of rules
7608 (extend (lambda (config rules)
7610 (($ <udev-configuration> udev initial-rules)
7612 (udev udev) ;the udev package to use
7613 (rules (append initial-rules rules)))))))))
7616 This is the service type for the
7617 @uref{https://wiki.gentoo.org/wiki/Project:Eudev, eudev device
7618 management daemon}. Compared to the previous example, in addition to an
7619 extension of @var{dmd-root-service-type}, we see two new fields:
7623 This is the procedure to @dfn{compose} the list of extensions to
7624 services of this type.
7626 Services can extend the udev service by passing it lists of rules; we
7627 compose those extensions simply by concatenating them.
7630 This procedure defines how the service's value is @dfn{extended} with
7631 the composition of the extensions.
7633 Udev extensions are composed into a list of rules, but the udev service
7634 value is itself a @code{<udev-configuration>} record. So here, we
7635 extend that record by appending the list of rules is contains to the
7636 list of contributed rules.
7639 There can be only one instance of an extensible service type such as
7640 @var{udev-service-type}. If there were more, the
7641 @code{service-extension} specifications would be ambiguous.
7643 Still here? The next section provides a reference of the programming
7644 interface for services.
7646 @node Service Reference
7647 @subsubsection Service Reference
7649 We have seen an overview of service types (@pxref{Service Types and
7650 Services}). This section provides a reference on how to manipulate
7651 services and service types. This interface is provided by the
7652 @code{(gnu services)} module.
7654 @deffn {Scheme Procedure} service @var{type} @var{value}
7655 Return a new service of @var{type}, a @code{<service-type>} object (see
7656 below.) @var{value} can be any object; it represents the parameters of
7657 this particular service instance.
7660 @deffn {Scheme Procedure} service? @var{obj}
7661 Return true if @var{obj} is a service.
7664 @deffn {Scheme Procedure} service-kind @var{service}
7665 Return the type of @var{service}---i.e., a @code{<service-type>} object.
7668 @deffn {Scheme Procedure} service-parameters @var{service}
7669 Return the value associated with @var{service}. It represents its
7673 Here is an example of how a service is created and manipulated:
7677 (service nginx-service-type
7678 (nginx-configuration
7680 (log-directory log-directory)
7681 (run-directory run-directory)
7682 (file config-file))))
7687 (eq? (service-kind s) nginx-service-type)
7691 The @code{modify-services} form provides a handy way to change the
7692 parameters of some of the services of a list such as
7693 @var{%base-services} (@pxref{Base Services, @code{%base-services}}). Of
7694 course, you could always use standard list combinators such as
7695 @code{map} and @code{fold} to do that (@pxref{SRFI-1, List Library,,
7696 guile, GNU Guile Reference Manual}); @code{modify-services} simply
7697 provides a more concise form for this common pattern.
7699 @deffn {Scheme Syntax} modify-services @var{services} @
7700 (@var{type} @var{variable} => @var{body}) @dots{}
7702 Modify the services listed in @var{services} according to the given
7703 clauses. Each clause has the form:
7706 (@var{type} @var{variable} => @var{body})
7709 where @var{type} is a service type, such as @var{guix-service-type}, and
7710 @var{variable} is an identifier that is bound within @var{body} to the
7711 value of the service of that @var{type}. @xref{Using the Configuration
7712 System}, for an example.
7714 This is a shorthand for:
7717 (map (lambda (service) @dots{}) @var{services})
7721 Next comes the programming interface for service types. This is
7722 something you want to know when writing new service definitions, but not
7723 necessarily when simply looking for ways to customize your
7724 @code{operating-system} declaration.
7726 @deftp {Data Type} service-type
7727 @cindex service type
7728 This is the representation of a @dfn{service type} (@pxref{Service Types
7733 This is a symbol, used only to simplify inspection and debugging.
7735 @item @code{extensions}
7736 A non-empty list of @code{<service-extension>} objects (see below.)
7738 @item @code{compose} (default: @code{#f})
7739 If this is @code{#f}, then the service type denotes services that cannot
7740 be extended---i.e., services that do not receive ``values'' from other
7743 Otherwise, it must be a one-argument procedure. The procedure is called
7744 by @code{fold-services} and is passed a list of values collected from
7745 extensions. It must return a value that is a valid parameter value for
7746 the service instance.
7748 @item @code{extend} (default: @code{#f})
7749 If this is @code{#f}, services of this type cannot be extended.
7751 Otherwise, it must be a two-argument procedure: @code{fold-services}
7752 calls it, passing it the service's initial value as the first argument
7753 and the result of applying @code{compose} to the extension values as the
7757 @xref{Service Types and Services}, for examples.
7760 @deffn {Scheme Procedure} service-extension @var{target-type} @
7762 Return a new extension for services of type @var{target-type}.
7763 @var{compute} must be a one-argument procedure: @code{fold-services}
7764 calls it, passing it the value associated with the service that provides
7765 the extension; it must return a valid value for the target service.
7768 @deffn {Scheme Procedure} service-extension? @var{obj}
7769 Return true if @var{obj} is a service extension.
7772 At the core of the service abstraction lies the @code{fold-services}
7773 procedure, which is responsible for ``compiling'' a list of services
7774 down to a single boot script. In essence, it propagates service
7775 extensions down the service graph, updating each node parameters on the
7776 way, until it reaches the root node.
7778 @deffn {Scheme Procedure} fold-services @var{services} @
7779 [#:target-type @var{boot-service-type}]
7780 Fold @var{services} by propagating their extensions down to the root of
7781 type @var{target-type}; return the root service adjusted accordingly.
7784 Lastly, the @code{(gnu services)} module also defines several essential
7785 service types, some of which are listed below.
7787 @defvr {Scheme Variable} boot-service-type
7788 The type of the ``boot service'', which is the root of the service
7792 @defvr {Scheme Variable} etc-service-type
7793 The type of the @file{/etc} service. This service can be extended by
7794 passing it name/file tuples such as:
7797 (list `("issue" ,(plain-file "issue" "Welcome!\n")))
7800 In this example, the effect would be to add an @file{/etc/issue} file
7801 pointing to the given file.
7804 @defvr {Scheme Variable} setuid-program-service-type
7805 Type for the ``setuid-program service''. This service collects lists of
7806 executable file names, passed as gexps, and adds them to the set of
7807 setuid-root programs on the system (@pxref{Setuid Programs}).
7812 @subsubsection dmd Services
7816 The @code{(gnu services dmd)} provides a way to define services managed
7817 by GNU@tie{}dmd, which is GuixSD initialization system---the first
7818 process that is started when the system boots, aka. PID@tie{}1
7819 (@pxref{Introduction,,, dmd, GNU dmd Manual}).
7821 Services in dmd can depend on each other. For instance, the SSH daemon
7822 may need to be started after the syslog daemon has been started, which
7823 in turn can only happen once all the file systems have been mounted.
7824 The simple operating system defined earlier (@pxref{Using the
7825 Configuration System}) results in a service graph like this:
7827 @image{images/dmd-graph,,5in,Typical dmd service graph.}
7829 You can actually generate such a graph for any operating system
7830 definition using the @command{guix system dmd-graph} command
7831 (@pxref{system-dmd-graph, @command{guix system dmd-graph}}).
7833 The @var{%dmd-root-service} is a service object representing PID@tie{}1,
7834 of type @var{dmd-root-service-type}; it can be extended by passing it
7835 lists of @code{<dmd-service>} objects.
7837 @deftp {Data Type} dmd-service
7838 The data type representing a service managed by dmd.
7841 @item @code{provision}
7842 This is a list of symbols denoting what the service provides.
7844 These are the names that may be passed to @command{deco start},
7845 @command{deco status}, and similar commands (@pxref{Invoking deco,,,
7846 dmd, GNU dmd Manual}). @xref{Slots of services, the @code{provides}
7847 slot,, dmd, GNU dmd Manual}, for details.
7849 @item @code{requirements} (default: @code{'()})
7850 List of symbols denoting the dmd services this one depends on.
7852 @item @code{respawn?} (default: @code{#t})
7853 Whether to restart the service when it stops, for instance when the
7854 underlying process dies.
7857 @itemx @code{stop} (default: @code{#~(const #f)})
7858 The @code{start} and @code{stop} fields refer to dmd's facilities to
7859 start and stop processes (@pxref{Service De- and Constructors,,, dmd,
7860 GNU dmd Manual}). They are given as G-expressions that get expanded in
7861 the dmd configuration file (@pxref{G-Expressions}).
7863 @item @code{documentation}
7864 A documentation string, as shown when running:
7867 deco doc @var{service-name}
7870 where @var{service-name} is one of the symbols in @var{provision}
7871 (@pxref{Invoking deco,,, dmd, GNU dmd Manual}).
7875 @defvr {Scheme Variable} dmd-root-service-type
7876 The service type for the dmd ``root service''---i.e., PID@tie{}1.
7878 This is the service type that extensions target when they want to create
7879 dmd services (@pxref{Service Types and Services}, for an example). Each
7880 extension must pass a list of @code{<dmd-service>}.
7883 @defvr {Scheme Variable} %dmd-root-service
7884 This service represents PID@tie{}1.
7888 @node Installing Debugging Files
7889 @section Installing Debugging Files
7891 @cindex debugging files
7892 Program binaries, as produced by the GCC compilers for instance, are
7893 typically written in the ELF format, with a section containing
7894 @dfn{debugging information}. Debugging information is what allows the
7895 debugger, GDB, to map binary code to source code; it is required to
7896 debug a compiled program in good conditions.
7898 The problem with debugging information is that is takes up a fair amount
7899 of disk space. For example, debugging information for the GNU C Library
7900 weighs in at more than 60 MiB. Thus, as a user, keeping all the
7901 debugging info of all the installed programs is usually not an option.
7902 Yet, space savings should not come at the cost of an impediment to
7903 debugging---especially in the GNU system, which should make it easier
7904 for users to exert their computing freedom (@pxref{GNU Distribution}).
7906 Thankfully, the GNU Binary Utilities (Binutils) and GDB provide a
7907 mechanism that allows users to get the best of both worlds: debugging
7908 information can be stripped from the binaries and stored in separate
7909 files. GDB is then able to load debugging information from those files,
7910 when they are available (@pxref{Separate Debug Files,,, gdb, Debugging
7913 The GNU distribution takes advantage of this by storing debugging
7914 information in the @code{lib/debug} sub-directory of a separate package
7915 output unimaginatively called @code{debug} (@pxref{Packages with
7916 Multiple Outputs}). Users can choose to install the @code{debug} output
7917 of a package when they need it. For instance, the following command
7918 installs the debugging information for the GNU C Library and for GNU
7922 guix package -i glibc:debug guile:debug
7925 GDB must then be told to look for debug files in the user's profile, by
7926 setting the @code{debug-file-directory} variable (consider setting it
7927 from the @file{~/.gdbinit} file, @pxref{Startup,,, gdb, Debugging with
7931 (gdb) set debug-file-directory ~/.guix-profile/lib/debug
7934 From there on, GDB will pick up debugging information from the
7935 @code{.debug} files under @file{~/.guix-profile/lib/debug}.
7937 In addition, you will most likely want GDB to be able to show the source
7938 code being debugged. To do that, you will have to unpack the source
7939 code of the package of interest (obtained with @code{guix build
7940 --source}, @pxref{Invoking guix build}), and to point GDB to that source
7941 directory using the @code{directory} command (@pxref{Source Path,
7942 @code{directory},, gdb, Debugging with GDB}).
7944 @c XXX: keep me up-to-date
7945 The @code{debug} output mechanism in Guix is implemented by the
7946 @code{gnu-build-system} (@pxref{Build Systems}). Currently, it is
7947 opt-in---debugging information is available only for those packages
7948 whose definition explicitly declares a @code{debug} output. This may be
7949 changed to opt-out in the future, if our build farm servers can handle
7950 the load. To check whether a package has a @code{debug} output, use
7951 @command{guix package --list-available} (@pxref{Invoking guix package}).
7954 @node Security Updates
7955 @section Security Updates
7958 As of version @value{VERSION}, the feature described in this section is
7962 @cindex security updates
7963 Occasionally, important security vulnerabilities are discovered in core
7964 software packages and must be patched. Guix follows a functional
7965 package management discipline (@pxref{Introduction}), which implies
7966 that, when a package is changed, @emph{every package that depends on it}
7967 must be rebuilt. This can significantly slow down the deployment of
7968 fixes in core packages such as libc or Bash, since basically the whole
7969 distribution would need to be rebuilt. Using pre-built binaries helps
7970 (@pxref{Substitutes}), but deployment may still take more time than
7974 To address that, Guix implements @dfn{grafts}, a mechanism that allows
7975 for fast deployment of critical updates without the costs associated
7976 with a whole-distribution rebuild. The idea is to rebuild only the
7977 package that needs to be patched, and then to ``graft'' it onto packages
7978 explicitly installed by the user and that were previously referring to
7979 the original package. The cost of grafting is typically very low, and
7980 order of magnitudes lower than a full rebuild of the dependency chain.
7982 @cindex replacements of packages, for grafts
7983 For instance, suppose a security update needs to be applied to Bash.
7984 Guix developers will provide a package definition for the ``fixed''
7985 Bash, say @var{bash-fixed}, in the usual way (@pxref{Defining
7986 Packages}). Then, the original package definition is augmented with a
7987 @code{replacement} field pointing to the package containing the bug fix:
7994 (replacement bash-fixed)))
7997 From there on, any package depending directly or indirectly on Bash that
7998 is installed will automatically be ``rewritten'' to refer to
7999 @var{bash-fixed} instead of @var{bash}. This grafting process takes
8000 time proportional to the size of the package, but expect less than a
8001 minute for an ``average'' package on a recent machine.
8003 Currently, the graft and the package it replaces (@var{bash-fixed} and
8004 @var{bash} in the example above) must have the exact same @code{name}
8005 and @code{version} fields. This restriction mostly comes from the fact
8006 that grafting works by patching files, including binary files, directly.
8007 Other restrictions may apply: for instance, when adding a graft to a
8008 package providing a shared library, the original shared library and its
8009 replacement must have the same @code{SONAME} and be binary-compatible.
8012 @node Package Modules
8013 @section Package Modules
8015 From a programming viewpoint, the package definitions of the
8016 GNU distribution are provided by Guile modules in the @code{(gnu packages
8017 @dots{})} name space@footnote{Note that packages under the @code{(gnu
8018 packages @dots{})} module name space are not necessarily ``GNU
8019 packages''. This module naming scheme follows the usual Guile module
8020 naming convention: @code{gnu} means that these modules are distributed
8021 as part of the GNU system, and @code{packages} identifies modules that
8022 define packages.} (@pxref{Modules, Guile modules,, guile, GNU Guile
8023 Reference Manual}). For instance, the @code{(gnu packages emacs)}
8024 module exports a variable named @code{emacs}, which is bound to a
8025 @code{<package>} object (@pxref{Defining Packages}).
8027 The @code{(gnu packages @dots{})} module name space is
8028 automatically scanned for packages by the command-line tools. For
8029 instance, when running @code{guix package -i emacs}, all the @code{(gnu
8030 packages @dots{})} modules are scanned until one that exports a package
8031 object whose name is @code{emacs} is found. This package search
8032 facility is implemented in the @code{(gnu packages)} module.
8034 @cindex customization, of packages
8035 @cindex package module search path
8036 Users can store package definitions in modules with different
8037 names---e.g., @code{(my-packages emacs)}@footnote{Note that the file
8038 name and module name must match. For instance, the @code{(my-packages
8039 emacs)} module must be stored in a @file{my-packages/emacs.scm} file
8040 relative to the load path specified with @option{--load-path} or
8041 @code{GUIX_PACKAGE_PATH}. @xref{Modules and the File System,,,
8042 guile, GNU Guile Reference Manual}, for details.}. These package definitions
8043 will not be visible by default. Thus, users can invoke commands such as
8044 @command{guix package} and @command{guix build} have to be used with the
8045 @code{-e} option so that they know where to find the package. Better
8046 yet, they can use the
8047 @code{-L} option of these commands to make those modules visible
8048 (@pxref{Invoking guix build, @code{--load-path}}), or define the
8049 @code{GUIX_PACKAGE_PATH} environment variable. This environment
8050 variable makes it easy to extend or customize the distribution and is
8051 honored by all the user interfaces.
8053 @defvr {Environment Variable} GUIX_PACKAGE_PATH
8054 This is a colon-separated list of directories to search for package
8055 modules. Directories listed in this variable take precedence over the
8056 distribution's own modules.
8059 The distribution is fully @dfn{bootstrapped} and @dfn{self-contained}:
8060 each package is built based solely on other packages in the
8061 distribution. The root of this dependency graph is a small set of
8062 @dfn{bootstrap binaries}, provided by the @code{(gnu packages
8063 bootstrap)} module. For more information on bootstrapping,
8064 @pxref{Bootstrapping}.
8066 @node Packaging Guidelines
8067 @section Packaging Guidelines
8069 The GNU distribution is nascent and may well lack some of your favorite
8070 packages. This section describes how you can help make the distribution
8071 grow. @xref{Contributing}, for additional information on how you can
8074 Free software packages are usually distributed in the form of
8075 @dfn{source code tarballs}---typically @file{tar.gz} files that contain
8076 all the source files. Adding a package to the distribution means
8077 essentially two things: adding a @dfn{recipe} that describes how to
8078 build the package, including a list of other packages required to build
8079 it, and adding @dfn{package meta-data} along with that recipe, such as a
8080 description and licensing information.
8082 In Guix all this information is embodied in @dfn{package definitions}.
8083 Package definitions provide a high-level view of the package. They are
8084 written using the syntax of the Scheme programming language; in fact,
8085 for each package we define a variable bound to the package definition,
8086 and export that variable from a module (@pxref{Package Modules}).
8087 However, in-depth Scheme knowledge is @emph{not} a prerequisite for
8088 creating packages. For more information on package definitions,
8089 @pxref{Defining Packages}.
8091 Once a package definition is in place, stored in a file in the Guix
8092 source tree, it can be tested using the @command{guix build} command
8093 (@pxref{Invoking guix build}). For example, assuming the new package is
8094 called @code{gnew}, you may run this command from the Guix build tree
8095 (@pxref{Running Guix Before It Is Installed}):
8098 ./pre-inst-env guix build gnew --keep-failed
8101 Using @code{--keep-failed} makes it easier to debug build failures since
8102 it provides access to the failed build tree. Another useful
8103 command-line option when debugging is @code{--log-file}, to access the
8106 If the package is unknown to the @command{guix} command, it may be that
8107 the source file contains a syntax error, or lacks a @code{define-public}
8108 clause to export the package variable. To figure it out, you may load
8109 the module from Guile to get more information about the actual error:
8112 ./pre-inst-env guile -c '(use-modules (gnu packages gnew))'
8115 Once your package builds correctly, please send us a patch
8116 (@pxref{Contributing}). Well, if you need help, we will be happy to
8117 help you too. Once the patch is committed in the Guix repository, the
8118 new package automatically gets built on the supported platforms by
8119 @url{http://hydra.gnu.org/jobset/gnu/master, our continuous integration
8123 Users can obtain the new package definition simply by running
8124 @command{guix pull} (@pxref{Invoking guix pull}). When
8125 @code{hydra.gnu.org} is done building the package, installing the
8126 package automatically downloads binaries from there
8127 (@pxref{Substitutes}). The only place where human intervention is
8128 needed is to review and apply the patch.
8132 * Software Freedom:: What may go into the distribution.
8133 * Package Naming:: What's in a name?
8134 * Version Numbers:: When the name is not enough.
8135 * Synopses and Descriptions:: Helping users find the right package.
8136 * Python Modules:: Taming the snake.
8137 * Perl Modules:: Little pearls.
8138 * Fonts:: Fond of fonts.
8141 @node Software Freedom
8142 @subsection Software Freedom
8144 @c Adapted from http://www.gnu.org/philosophy/philosophy.html.
8146 The GNU operating system has been developed so that users can have
8147 freedom in their computing. GNU is @dfn{free software}, meaning that
8148 users have the @url{http://www.gnu.org/philosophy/free-sw.html,four
8149 essential freedoms}: to run the program, to study and change the program
8150 in source code form, to redistribute exact copies, and to distribute
8151 modified versions. Packages found in the GNU distribution provide only
8152 software that conveys these four freedoms.
8154 In addition, the GNU distribution follow the
8155 @url{http://www.gnu.org/distros/free-system-distribution-guidelines.html,free
8156 software distribution guidelines}. Among other things, these guidelines
8157 reject non-free firmware, recommendations of non-free software, and
8158 discuss ways to deal with trademarks and patents.
8160 Some packages contain a small and optional subset that violates the
8161 above guidelines, for instance because this subset is itself non-free
8162 code. When that happens, the offending items are removed with
8163 appropriate patches or code snippets in the package definition's
8164 @code{origin} form (@pxref{Defining Packages}). That way, @code{guix
8165 build --source} returns the ``freed'' source rather than the unmodified
8169 @node Package Naming
8170 @subsection Package Naming
8172 A package has actually two names associated with it:
8173 First, there is the name of the @emph{Scheme variable}, the one following
8174 @code{define-public}. By this name, the package can be made known in the
8175 Scheme code, for instance as input to another package. Second, there is
8176 the string in the @code{name} field of a package definition. This name
8177 is used by package management commands such as
8178 @command{guix package} and @command{guix build}.
8180 Both are usually the same and correspond to the lowercase conversion of
8181 the project name chosen upstream, with underscores replaced with
8182 hyphens. For instance, GNUnet is available as @code{gnunet}, and
8183 SDL_net as @code{sdl-net}.
8185 We do not add @code{lib} prefixes for library packages, unless these are
8186 already part of the official project name. But @pxref{Python
8187 Modules} and @ref{Perl Modules} for special rules concerning modules for
8188 the Python and Perl languages.
8190 Font package names are handled differently, @pxref{Fonts}.
8193 @node Version Numbers
8194 @subsection Version Numbers
8196 We usually package only the latest version of a given free software
8197 project. But sometimes, for instance for incompatible library versions,
8198 two (or more) versions of the same package are needed. These require
8199 different Scheme variable names. We use the name as defined
8200 in @ref{Package Naming}
8201 for the most recent version; previous versions use the same name, suffixed
8202 by @code{-} and the smallest prefix of the version number that may
8203 distinguish the two versions.
8205 The name inside the package definition is the same for all versions of a
8206 package and does not contain any version number.
8208 For instance, the versions 2.24.20 and 3.9.12 of GTK+ may be packaged as follows:
8216 (define-public gtk+-2
8222 If we also wanted GTK+ 3.8.2, this would be packaged as
8224 (define-public gtk+-3.8
8231 @node Synopses and Descriptions
8232 @subsection Synopses and Descriptions
8234 As we have seen before, each package in GNU@tie{}Guix includes a
8235 synopsis and a description (@pxref{Defining Packages}). Synopses and
8236 descriptions are important: They are what @command{guix package
8237 --search} searches, and a crucial piece of information to help users
8238 determine whether a given package suits their needs. Consequently,
8239 packagers should pay attention to what goes into them.
8241 Synopses must start with a capital letter and must not end with a
8242 period. They must not start with ``a'' or ``the'', which usually does
8243 not bring anything; for instance, prefer ``File-frobbing tool'' over ``A
8244 tool that frobs files''. The synopsis should say what the package
8245 is---e.g., ``Core GNU utilities (file, text, shell)''---or what it is
8246 used for---e.g., the synopsis for GNU@tie{}grep is ``Print lines
8247 matching a pattern''.
8249 Keep in mind that the synopsis must be meaningful for a very wide
8250 audience. For example, ``Manipulate alignments in the SAM format''
8251 might make sense for a seasoned bioinformatics researcher, but might be
8252 fairly unhelpful or even misleading to a non-specialized audience. It
8253 is a good idea to come up with a synopsis that gives an idea of the
8254 application domain of the package. In this example, this might give
8255 something like ``Manipulate nucleotide sequence alignments'', which
8256 hopefully gives the user a better idea of whether this is what they are
8259 @cindex Texinfo markup, in package descriptions
8260 Descriptions should take between five and ten lines. Use full
8261 sentences, and avoid using acronyms without first introducing them.
8262 Descriptions can include Texinfo markup, which is useful to introduce
8263 ornaments such as @code{@@code} or @code{@@dfn}, bullet lists, or
8264 hyperlinks (@pxref{Overview,,, texinfo, GNU Texinfo}). However you
8265 should be careful when using some characters for example @samp{@@} and
8266 curly braces which are the basic special characters in Texinfo
8267 (@pxref{Special Characters,,, texinfo, GNU Texinfo}). User interfaces
8268 such as @command{guix package --show} take care of rendering it
8271 Synopses and descriptions are translated by volunteers
8272 @uref{http://translationproject.org/domain/guix-packages.html, at the
8273 Translation Project} so that as many users as possible can read them in
8274 their native language. User interfaces search them and display them in
8275 the language specified by the current locale.
8277 Translation is a lot of work so, as a packager, please pay even more
8278 attention to your synopses and descriptions as every change may entail
8279 additional work for translators. In order to help them, it is possible
8280 to make recommendations or instructions visible to them by inserting
8281 special comments like this (@pxref{xgettext Invocation,,, gettext, GNU
8285 ;; TRANSLATORS: "X11 resize-and-rotate" should not be translated.
8286 (description "ARandR is designed to provide a simple visual front end
8287 for the X11 resize-and-rotate (RandR) extension. @dots{}")
8291 @node Python Modules
8292 @subsection Python Modules
8294 We currently package Python 2 and Python 3, under the Scheme variable names
8295 @code{python-2} and @code{python} as explained in @ref{Version Numbers}.
8296 To avoid confusion and naming clashes with other programming languages, it
8297 seems desirable that the name of a package for a Python module contains
8298 the word @code{python}.
8300 Some modules are compatible with only one version of Python, others with both.
8301 If the package Foo compiles only with Python 3, we name it
8302 @code{python-foo}; if it compiles only with Python 2, we name it
8303 @code{python2-foo}. If it is compatible with both versions, we create two
8304 packages with the corresponding names.
8306 If a project already contains the word @code{python}, we drop this;
8307 for instance, the module python-dateutil is packaged under the names
8308 @code{python-dateutil} and @code{python2-dateutil}.
8312 @subsection Perl Modules
8314 Perl programs standing for themselves are named as any other package,
8315 using the lowercase upstream name.
8316 For Perl packages containing a single class, we use the lowercase class name,
8317 replace all occurrences of @code{::} by dashes and prepend the prefix
8319 So the class @code{XML::Parser} becomes @code{perl-xml-parser}.
8320 Modules containing several classes keep their lowercase upstream name and
8321 are also prepended by @code{perl-}. Such modules tend to have the word
8322 @code{perl} somewhere in their name, which gets dropped in favor of the
8323 prefix. For instance, @code{libwww-perl} becomes @code{perl-libwww}.
8329 For fonts that are in general not installed by a user for typesetting
8330 purposes, or that are distributed as part of a larger software package,
8331 we rely on the general packaging rules for software; for instance, this
8332 applies to the fonts delivered as part of the X.Org system or fonts that
8333 are part of TeX Live.
8335 To make it easier for a user to search for fonts, names for other packages
8336 containing only fonts are constructed as follows, independently of the
8337 upstream package name.
8339 The name of a package containing only one font family starts with
8340 @code{font-}; it is followed by the foundry name and a dash @code{-}
8341 if the foundry is known, and the font family name, in which spaces are
8342 replaced by dashes (and as usual, all upper case letters are transformed
8344 For example, the Gentium font family by SIL is packaged under the name
8345 @code{font-sil-gentium}.
8347 For a package containing several font families, the name of the collection
8348 is used in the place of the font family name.
8349 For instance, the Liberation fonts consist of three families,
8350 Liberation Sans, Liberation Serif and Liberation Mono.
8351 These could be packaged separately under the names
8352 @code{font-liberation-sans} and so on; but as they are distributed together
8353 under a common name, we prefer to package them together as
8354 @code{font-liberation}.
8356 In the case where several formats of the same font family or font collection
8357 are packaged separately, a short form of the format, prepended by a dash,
8358 is added to the package name. We use @code{-ttf} for TrueType fonts,
8359 @code{-otf} for OpenType fonts and @code{-type1} for PostScript Type 1
8365 @section Bootstrapping
8367 @c Adapted from the ELS 2013 paper.
8369 @cindex bootstrapping
8371 Bootstrapping in our context refers to how the distribution gets built
8372 ``from nothing''. Remember that the build environment of a derivation
8373 contains nothing but its declared inputs (@pxref{Introduction}). So
8374 there's an obvious chicken-and-egg problem: how does the first package
8375 get built? How does the first compiler get compiled? Note that this is
8376 a question of interest only to the curious hacker, not to the regular
8377 user, so you can shamelessly skip this section if you consider yourself
8380 @cindex bootstrap binaries
8381 The GNU system is primarily made of C code, with libc at its core. The
8382 GNU build system itself assumes the availability of a Bourne shell and
8383 command-line tools provided by GNU Coreutils, Awk, Findutils, `sed', and
8384 `grep'. Furthermore, build programs---programs that run
8385 @code{./configure}, @code{make}, etc.---are written in Guile Scheme
8386 (@pxref{Derivations}). Consequently, to be able to build anything at
8387 all, from scratch, Guix relies on pre-built binaries of Guile, GCC,
8388 Binutils, libc, and the other packages mentioned above---the
8389 @dfn{bootstrap binaries}.
8391 These bootstrap binaries are ``taken for granted'', though we can also
8392 re-create them if needed (more on that later).
8394 @unnumberedsubsec Preparing to Use the Bootstrap Binaries
8396 @c As of Emacs 24.3, Info-mode displays the image, but since it's a
8397 @c large image, it's hard to scroll. Oh well.
8398 @image{images/bootstrap-graph,6in,,Dependency graph of the early bootstrap derivations}
8400 The figure above shows the very beginning of the dependency graph of the
8401 distribution, corresponding to the package definitions of the @code{(gnu
8402 packages bootstrap)} module. At this level of detail, things are
8403 slightly complex. First, Guile itself consists of an ELF executable,
8404 along with many source and compiled Scheme files that are dynamically
8405 loaded when it runs. This gets stored in the @file{guile-2.0.7.tar.xz}
8406 tarball shown in this graph. This tarball is part of Guix's ``source''
8407 distribution, and gets inserted into the store with @code{add-to-store}
8408 (@pxref{The Store}).
8410 But how do we write a derivation that unpacks this tarball and adds it
8411 to the store? To solve this problem, the @code{guile-bootstrap-2.0.drv}
8412 derivation---the first one that gets built---uses @code{bash} as its
8413 builder, which runs @code{build-bootstrap-guile.sh}, which in turn calls
8414 @code{tar} to unpack the tarball. Thus, @file{bash}, @file{tar},
8415 @file{xz}, and @file{mkdir} are statically-linked binaries, also part of
8416 the Guix source distribution, whose sole purpose is to allow the Guile
8417 tarball to be unpacked.
8419 Once @code{guile-bootstrap-2.0.drv} is built, we have a functioning
8420 Guile that can be used to run subsequent build programs. Its first task
8421 is to download tarballs containing the other pre-built binaries---this
8422 is what the @code{.tar.xz.drv} derivations do. Guix modules such as
8423 @code{ftp-client.scm} are used for this purpose. The
8424 @code{module-import.drv} derivations import those modules in a directory
8425 in the store, using the original layout. The
8426 @code{module-import-compiled.drv} derivations compile those modules, and
8427 write them in an output directory with the right layout. This
8428 corresponds to the @code{#:modules} argument of
8429 @code{build-expression->derivation} (@pxref{Derivations}).
8431 Finally, the various tarballs are unpacked by the
8432 derivations @code{gcc-bootstrap-0.drv}, @code{glibc-bootstrap-0.drv},
8433 etc., at which point we have a working C tool chain.
8436 @unnumberedsubsec Building the Build Tools
8438 @c TODO: Add a package-level dependency graph generated from (gnu
8441 Bootstrapping is complete when we have a full tool chain that does not
8442 depend on the pre-built bootstrap tools discussed above. This
8443 no-dependency requirement is verified by checking whether the files of
8444 the final tool chain contain references to the @file{/gnu/store}
8445 directories of the bootstrap inputs. The process that leads to this
8446 ``final'' tool chain is described by the package definitions found in
8447 the @code{(gnu packages commencement)} module.
8449 @c See <http://lists.gnu.org/archive/html/gnu-system-discuss/2012-10/msg00000.html>.
8450 The first tool that gets built with the bootstrap binaries is
8451 GNU Make, which is a prerequisite for all the following packages.
8452 From there Findutils and Diffutils get built.
8454 Then come the first-stage Binutils and GCC, built as pseudo cross
8455 tools---i.e., with @code{--target} equal to @code{--host}. They are
8456 used to build libc. Thanks to this cross-build trick, this libc is
8457 guaranteed not to hold any reference to the initial tool chain.
8459 From there the final Binutils and GCC are built. GCC uses @code{ld}
8460 from the final Binutils, and links programs against the just-built libc.
8461 This tool chain is used to build the other packages used by Guix and by
8462 the GNU Build System: Guile, Bash, Coreutils, etc.
8464 And voilà! At this point we have the complete set of build tools that
8465 the GNU Build System expects. These are in the @code{%final-inputs}
8466 variable of the @code{(gnu packages commencement)} module, and are
8467 implicitly used by any package that uses @code{gnu-build-system}
8468 (@pxref{Build Systems, @code{gnu-build-system}}).
8471 @unnumberedsubsec Building the Bootstrap Binaries
8473 Because the final tool chain does not depend on the bootstrap binaries,
8474 those rarely need to be updated. Nevertheless, it is useful to have an
8475 automated way to produce them, should an update occur, and this is what
8476 the @code{(gnu packages make-bootstrap)} module provides.
8478 The following command builds the tarballs containing the bootstrap
8479 binaries (Guile, Binutils, GCC, libc, and a tarball containing a mixture
8480 of Coreutils and other basic command-line tools):
8483 guix build bootstrap-tarballs
8486 The generated tarballs are those that should be referred to in the
8487 @code{(gnu packages bootstrap)} module mentioned at the beginning of
8490 Still here? Then perhaps by now you've started to wonder: when do we
8491 reach a fixed point? That is an interesting question! The answer is
8492 unknown, but if you would like to investigate further (and have
8493 significant computational and storage resources to do so), then let us
8497 @section Porting to a New Platform
8499 As discussed above, the GNU distribution is self-contained, and
8500 self-containment is achieved by relying on pre-built ``bootstrap
8501 binaries'' (@pxref{Bootstrapping}). These binaries are specific to an
8502 operating system kernel, CPU architecture, and application binary
8503 interface (ABI). Thus, to port the distribution to a platform that is
8504 not yet supported, one must build those bootstrap binaries, and update
8505 the @code{(gnu packages bootstrap)} module to use them on that platform.
8507 Fortunately, Guix can @emph{cross compile} those bootstrap binaries.
8508 When everything goes well, and assuming the GNU tool chain supports the
8509 target platform, this can be as simple as running a command like this
8513 guix build --target=armv5tel-linux-gnueabi bootstrap-tarballs
8516 For this to work, the @code{glibc-dynamic-linker} procedure in
8517 @code{(gnu packages bootstrap)} must be augmented to return the right
8518 file name for libc's dynamic linker on that platform; likewise,
8519 @code{system->linux-architecture} in @code{(gnu packages linux)} must be
8520 taught about the new platform.
8522 Once these are built, the @code{(gnu packages bootstrap)} module needs
8523 to be updated to refer to these binaries on the target platform. That
8524 is, the hashes and URLs of the bootstrap tarballs for the new platform
8525 must be added alongside those of the currently supported platforms. The
8526 bootstrap Guile tarball is treated specially: it is expected to be
8527 available locally, and @file{gnu-system.am} has rules do download it for
8528 the supported architectures; a rule for the new platform must be added
8531 In practice, there may be some complications. First, it may be that the
8532 extended GNU triplet that specifies an ABI (like the @code{eabi} suffix
8533 above) is not recognized by all the GNU tools. Typically, glibc
8534 recognizes some of these, whereas GCC uses an extra @code{--with-abi}
8535 configure flag (see @code{gcc.scm} for examples of how to handle this).
8536 Second, some of the required packages could fail to build for that
8537 platform. Lastly, the generated binaries could be broken for some
8540 @c *********************************************************************
8541 @include contributing.texi
8543 @c *********************************************************************
8544 @node Acknowledgments
8545 @chapter Acknowledgments
8547 Guix is based on the @uref{http://nixos.org/nix/, Nix package manager},
8548 which was designed and
8549 implemented by Eelco Dolstra, with contributions from other people (see
8550 the @file{nix/AUTHORS} file in Guix.) Nix pioneered functional package
8551 management, and promoted unprecedented features, such as transactional
8552 package upgrades and rollbacks, per-user profiles, and referentially
8553 transparent build processes. Without this work, Guix would not exist.
8555 The Nix-based software distributions, Nixpkgs and NixOS, have also been
8556 an inspiration for Guix.
8558 GNU@tie{}Guix itself is a collective work with contributions from a
8559 number of people. See the @file{AUTHORS} file in Guix for more
8560 information on these fine people. The @file{THANKS} file lists people
8561 who have helped by reporting bugs, taking care of the infrastructure,
8562 providing artwork and themes, making suggestions, and more---thank you!
8565 @c *********************************************************************
8566 @node GNU Free Documentation License
8567 @appendix GNU Free Documentation License
8569 @include fdl-1.3.texi
8571 @c *********************************************************************
8573 @unnumbered Concept Index
8576 @node Programming Index
8577 @unnumbered Programming Index
8585 @c ispell-local-dictionary: "american";