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1 Linux kernel release 2.6.xx
3 These are the release notes for Linux version 2.6. Read them carefully,
4 as they tell you what this is all about, explain how to install the
5 kernel, and what to do if something goes wrong.
7 WHAT IS LINUX?
9 Linux is a Unix clone written from scratch by Linus Torvalds with
10 assistance from a loosely-knit team of hackers across the Net.
11 It aims towards POSIX compliance.
13 It has all the features you would expect in a modern fully-fledged
14 Unix, including true multitasking, virtual memory, shared libraries,
15 demand loading, shared copy-on-write executables, proper memory
16 management and TCP/IP networking.
18 It is distributed under the GNU General Public License - see the
19 accompanying COPYING file for more details.
21 ON WHAT HARDWARE DOES IT RUN?
23 Linux was first developed for 386/486-based PCs. These days it also
24 runs on ARMs, DEC Alphas, SUN Sparcs, M68000 machines (like Atari and
25 Amiga), MIPS and PowerPC, and others.
27 DOCUMENTATION:
29 - There is a lot of documentation available both in electronic form on
30 the Internet and in books, both Linux-specific and pertaining to
31 general UNIX questions. I'd recommend looking into the documentation
32 subdirectories on any Linux FTP site for the LDP (Linux Documentation
33 Project) books. This README is not meant to be documentation on the
34 system: there are much better sources available.
36 - There are various README files in the Documentation/ subdirectory:
37 these typically contain kernel-specific installation notes for some
38 drivers for example. See Documentation/00-INDEX for a list of what
39 is contained in each file. Please read the Changes file, as it
40 contains information about the problems, which may result by upgrading
41 your kernel.
43 - The Documentation/DocBook/ subdirectory contains several guides for
44 kernel developers and users. These guides can be rendered in a
45 number of formats: PostScript (.ps), PDF, and HTML, among others.
46 After installation, "make psdocs", "make pdfdocs", or "make htmldocs"
47 will render the documentation in the requested format.
49 INSTALLING the kernel:
51 - If you install the full sources, put the kernel tarball in a
52 directory where you have permissions (eg. your home directory) and
53 unpack it:
55 gzip -cd linux-2.6.XX.tar.gz | tar xvf -
57 Replace "XX" with the version number of the latest kernel.
59 Do NOT use the /usr/src/linux area! This area has a (usually
60 incomplete) set of kernel headers that are used by the library header
61 files. They should match the library, and not get messed up by
62 whatever the kernel-du-jour happens to be.
64 - You can also upgrade between 2.6.xx releases by patching. Patches are
65 distributed in the traditional gzip and the new bzip2 format. To
66 install by patching, get all the newer patch files, enter the
67 top level directory of the kernel source (linux-2.6.xx) and execute:
69 gzip -cd ../patch-2.6.xx.gz | patch -p1
71 or
72 bzip2 -dc ../patch-2.6.xx.bz2 | patch -p1
74 (repeat xx for all versions bigger than the version of your current
75 source tree, _in_order_) and you should be ok. You may want to remove
76 the backup files (xxx~ or xxx.orig), and make sure that there are no
77 failed patches (xxx# or xxx.rej). If there are, either you or me has
78 made a mistake.
80 Alternatively, the script patch-kernel can be used to automate this
81 process. It determines the current kernel version and applies any
82 patches found.
84 linux/scripts/patch-kernel linux
86 The first argument in the command above is the location of the
87 kernel source. Patches are applied from the current directory, but
88 an alternative directory can be specified as the second argument.
90 - If you are upgrading between releases using the stable series patches
91 (for example, patch-2.6.xx.y), note that these "dot-releases" are
92 not incremental and must be applied to the 2.6.xx base tree. For
93 example, if your base kernel is 2.6.12 and you want to apply the
94 2.6.12.3 patch, you do not and indeed must not first apply the
95 2.6.12.1 and 2.6.12.2 patches. Similarly, if you are running kernel
96 version 2.6.12.2 and want to jump to 2.6.12.3, you must first
97 reverse the 2.6.12.2 patch (that is, patch -R) _before_ applying
98 the 2.6.12.3 patch.
100 - Make sure you have no stale .o files and dependencies lying around:
102 cd linux
103 make mrproper
105 You should now have the sources correctly installed.
107 SOFTWARE REQUIREMENTS
109 Compiling and running the 2.6.xx kernels requires up-to-date
110 versions of various software packages. Consult
111 Documentation/Changes for the minimum version numbers required
112 and how to get updates for these packages. Beware that using
113 excessively old versions of these packages can cause indirect
114 errors that are very difficult to track down, so don't assume that
115 you can just update packages when obvious problems arise during
116 build or operation.
118 BUILD directory for the kernel:
120 When compiling the kernel all output files will per default be
121 stored together with the kernel source code.
122 Using the option "make O=output/dir" allow you to specify an alternate
123 place for the output files (including .config).
124 Example:
125 kernel source code: /usr/src/linux-2.6.N
126 build directory: /home/name/build/kernel
128 To configure and build the kernel use:
129 cd /usr/src/linux-2.6.N
130 make O=/home/name/build/kernel menuconfig
131 make O=/home/name/build/kernel
132 sudo make O=/home/name/build/kernel modules_install install
134 Please note: If the 'O=output/dir' option is used then it must be
135 used for all invocations of make.
137 CONFIGURING the kernel:
139 Do not skip this step even if you are only upgrading one minor
140 version. New configuration options are added in each release, and
141 odd problems will turn up if the configuration files are not set up
142 as expected. If you want to carry your existing configuration to a
143 new version with minimal work, use "make oldconfig", which will
144 only ask you for the answers to new questions.
146 - Alternate configuration commands are:
147 "make menuconfig" Text based color menus, radiolists & dialogs.
148 "make xconfig" X windows (Qt) based configuration tool.
149 "make gconfig" X windows (Gtk) based configuration tool.
150 "make oldconfig" Default all questions based on the contents of
151 your existing ./.config file.
153 NOTES on "make config":
154 - having unnecessary drivers will make the kernel bigger, and can
155 under some circumstances lead to problems: probing for a
156 nonexistent controller card may confuse your other controllers
157 - compiling the kernel with "Processor type" set higher than 386
158 will result in a kernel that does NOT work on a 386. The
159 kernel will detect this on bootup, and give up.
160 - A kernel with math-emulation compiled in will still use the
161 coprocessor if one is present: the math emulation will just
162 never get used in that case. The kernel will be slightly larger,
163 but will work on different machines regardless of whether they
164 have a math coprocessor or not.
165 - the "kernel hacking" configuration details usually result in a
166 bigger or slower kernel (or both), and can even make the kernel
167 less stable by configuring some routines to actively try to
168 break bad code to find kernel problems (kmalloc()). Thus you
169 should probably answer 'n' to the questions for
170 "development", "experimental", or "debugging" features.
172 - Check the top Makefile for further site-dependent configuration
173 (default SVGA mode etc).
175 COMPILING the kernel:
177 - Make sure you have gcc 2.95.3 available.
178 gcc 2.91.66 (egcs-1.1.2), and gcc 2.7.2.3 are known to miscompile
179 some parts of the kernel, and are *no longer supported*.
180 Also remember to upgrade your binutils package (for as/ld/nm and company)
181 if necessary. For more information, refer to Documentation/Changes.
183 Please note that you can still run a.out user programs with this kernel.
185 - Do a "make" to create a compressed kernel image. It is also
186 possible to do "make install" if you have lilo installed to suit the
187 kernel makefiles, but you may want to check your particular lilo setup first.
189 To do the actual install you have to be root, but none of the normal
190 build should require that. Don't take the name of root in vain.
192 - If you configured any of the parts of the kernel as `modules', you
193 will also have to do "make modules_install".
195 - Keep a backup kernel handy in case something goes wrong. This is
196 especially true for the development releases, since each new release
197 contains new code which has not been debugged. Make sure you keep a
198 backup of the modules corresponding to that kernel, as well. If you
199 are installing a new kernel with the same version number as your
200 working kernel, make a backup of your modules directory before you
201 do a "make modules_install".
203 - In order to boot your new kernel, you'll need to copy the kernel
204 image (e.g. .../linux/arch/i386/boot/bzImage after compilation)
205 to the place where your regular bootable kernel is found.
207 - Booting a kernel directly from a floppy without the assistance of a
208 bootloader such as LILO, is no longer supported.
210 If you boot Linux from the hard drive, chances are you use LILO which
211 uses the kernel image as specified in the file /etc/lilo.conf. The
212 kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or
213 /boot/bzImage. To use the new kernel, save a copy of the old image
214 and copy the new image over the old one. Then, you MUST RERUN LILO
215 to update the loading map!! If you don't, you won't be able to boot
216 the new kernel image.
218 Reinstalling LILO is usually a matter of running /sbin/lilo.
219 You may wish to edit /etc/lilo.conf to specify an entry for your
220 old kernel image (say, /vmlinux.old) in case the new one does not
221 work. See the LILO docs for more information.
223 After reinstalling LILO, you should be all set. Shutdown the system,
224 reboot, and enjoy!
226 If you ever need to change the default root device, video mode,
227 ramdisk size, etc. in the kernel image, use the 'rdev' program (or
228 alternatively the LILO boot options when appropriate). No need to
229 recompile the kernel to change these parameters.
231 - Reboot with the new kernel and enjoy.
233 IF SOMETHING GOES WRONG:
235 - If you have problems that seem to be due to kernel bugs, please check
236 the file MAINTAINERS to see if there is a particular person associated
237 with the part of the kernel that you are having trouble with. If there
238 isn't anyone listed there, then the second best thing is to mail
239 them to me (torvalds@osdl.org), and possibly to any other relevant
240 mailing-list or to the newsgroup.
242 - In all bug-reports, *please* tell what kernel you are talking about,
243 how to duplicate the problem, and what your setup is (use your common
244 sense). If the problem is new, tell me so, and if the problem is
245 old, please try to tell me when you first noticed it.
247 - If the bug results in a message like
249 unable to handle kernel paging request at address C0000010
250 Oops: 0002
251 EIP: 0010:XXXXXXXX
252 eax: xxxxxxxx ebx: xxxxxxxx ecx: xxxxxxxx edx: xxxxxxxx
253 esi: xxxxxxxx edi: xxxxxxxx ebp: xxxxxxxx
254 ds: xxxx es: xxxx fs: xxxx gs: xxxx
255 Pid: xx, process nr: xx
256 xx xx xx xx xx xx xx xx xx xx
258 or similar kernel debugging information on your screen or in your
259 system log, please duplicate it *exactly*. The dump may look
260 incomprehensible to you, but it does contain information that may
261 help debugging the problem. The text above the dump is also
262 important: it tells something about why the kernel dumped code (in
263 the above example it's due to a bad kernel pointer). More information
264 on making sense of the dump is in Documentation/oops-tracing.txt
266 - If you compiled the kernel with CONFIG_KALLSYMS you can send the dump
267 as is, otherwise you will have to use the "ksymoops" program to make
268 sense of the dump. This utility can be downloaded from
269 ftp://ftp.<country>.kernel.org/pub/linux/utils/kernel/ksymoops.
270 Alternately you can do the dump lookup by hand:
272 - In debugging dumps like the above, it helps enormously if you can
273 look up what the EIP value means. The hex value as such doesn't help
274 me or anybody else very much: it will depend on your particular
275 kernel setup. What you should do is take the hex value from the EIP
276 line (ignore the "0010:"), and look it up in the kernel namelist to
277 see which kernel function contains the offending address.
279 To find out the kernel function name, you'll need to find the system
280 binary associated with the kernel that exhibited the symptom. This is
281 the file 'linux/vmlinux'. To extract the namelist and match it against
282 the EIP from the kernel crash, do:
284 nm vmlinux | sort | less
286 This will give you a list of kernel addresses sorted in ascending
287 order, from which it is simple to find the function that contains the
288 offending address. Note that the address given by the kernel
289 debugging messages will not necessarily match exactly with the
290 function addresses (in fact, that is very unlikely), so you can't
291 just 'grep' the list: the list will, however, give you the starting
292 point of each kernel function, so by looking for the function that
293 has a starting address lower than the one you are searching for but
294 is followed by a function with a higher address you will find the one
295 you want. In fact, it may be a good idea to include a bit of
296 "context" in your problem report, giving a few lines around the
297 interesting one.
299 If you for some reason cannot do the above (you have a pre-compiled
300 kernel image or similar), telling me as much about your setup as
301 possible will help.
303 - Alternately, you can use gdb on a running kernel. (read-only; i.e. you
304 cannot change values or set break points.) To do this, first compile the
305 kernel with -g; edit arch/i386/Makefile appropriately, then do a "make
306 clean". You'll also need to enable CONFIG_PROC_FS (via "make config").
308 After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore".
309 You can now use all the usual gdb commands. The command to look up the
310 point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes
311 with the EIP value.)
313 gdb'ing a non-running kernel currently fails because gdb (wrongly)
314 disregards the starting offset for which the kernel is compiled.