1 GNU Linux-libre <http://linux-libre.fsfla.org>
2 ==============================================
4 These are the release notes for GNU Linux-libre. Read them carefully,
5 as they tell you what this is all about, explain how to install the
6 kernel, and what to do if something goes wrong.
8 What is GNU Linux-libre?
9 ------------------------
11 GNU Linux-libre is a Free version of the kernel Linux (see below),
12 suitable for use with the GNU Operating System in 100% Free
13 GNU/Linux-libre System Distributions.
14 http://www.gnu.org/distros/
16 It removes non-Free components from Linux, that are disguised as
17 source code or distributed in separate files. It also disables
18 run-time requests for non-Free components, shipped separately or as
19 part of Linux, and documentation pointing to them, so as to avoid
20 (Free-)baiting users into the trap of non-Free Software.
21 http://www.fsfla.org/anuncio/2010-11-Linux-2.6.36-libre-debait
23 Linux-libre started within the gNewSense GNU/Linux distribution.
24 It was later adopted by Jeff Moe, who coined its name, and in 2008
25 it became a project maintained by FSF Latin America. In 2012, it
26 became part of the GNU Project.
28 The GNU Linux-libre project takes a minimal-changes approach to
29 cleaning up Linux, making no effort to substitute components that
30 need to be removed with functionally equivalent Free ones.
31 Nevertheless, we encourage and support efforts towards doing so.
32 http://libreplanet.org/wiki/LinuxLibre:Devices_that_require_non-free_firmware
34 Our mascot is Freedo, a light-blue penguin that has just come out
35 of the shower. Although we like penguins, GNU is a much greater
36 contribution to the entire system, so its mascot deserves more
37 promotion. See our web page for their images.
38 http://linux-libre.fsfla.org/
40 If you are the author of an awesome program and want to join us in
41 writing Free (libre) Software, please consider making it an official
42 GNU program and become a GNU Maintainer. You can find instructions
43 on how to do so at https://www.gnu.org/help/evaluation. We look
44 forward to hacking with you! :)
49 Linux is a clone of the Unix kernel, written from scratch by
50 Linus Torvalds with assistance from a loosely-knit team of hackers across
51 the Net. It aims towards POSIX and Single UNIX Specification compliance.
53 It has all the features you would expect in a modern fully-fledged Unix kernel,
54 including true multitasking, virtual memory, shared libraries, demand
55 loading, shared copy-on-write executables, proper memory management,
56 and multistack networking including IPv4 and IPv6.
58 It is distributed under the GNU General Public License v2 - see the
59 accompanying COPYING file for more details.
61 On what hardware does it run?
62 -----------------------------
64 Although originally developed first for 32-bit x86-based PCs (386 or higher),
65 today Linux also runs on (at least) the Compaq Alpha AXP, Sun SPARC and
66 UltraSPARC, Motorola 68000, PowerPC, PowerPC64, ARM, Hitachi SuperH, Cell,
67 IBM S/390, MIPS, HP PA-RISC, Intel IA-64, DEC VAX, AMD x86-64, AXIS CRIS,
68 Xtensa, Tilera TILE, ARC and Renesas M32R architectures.
70 Linux is easily portable to most general-purpose 32- or 64-bit architectures
71 as long as they have a paged memory management unit (PMMU) and a port of the
72 GNU C compiler (gcc) (part of The GNU Compiler Collection, GCC). Linux has
73 also been ported to a number of architectures without a PMMU, although
74 functionality is then obviously somewhat limited.
75 Linux has also been ported to itself. You can now run the kernel as a
76 userspace application - this is called UserMode Linux (UML).
81 - There is a lot of documentation available both in electronic form on
82 the Internet and in books, both Linux-specific and pertaining to
83 general UNIX questions. I'd recommend looking into the documentation
84 subdirectories on any Linux FTP site for the LDP (Linux Documentation
85 Project) books. This README is not meant to be documentation on the
86 system: there are much better sources available.
88 - There are various README files in the Documentation/ subdirectory:
89 these typically contain kernel-specific installation notes for some
90 drivers for example. See Documentation/00-INDEX for a list of what
91 is contained in each file. Please read the
92 :ref:`Documentation/process/changes.rst <changes>` file, as it
93 contains information about the problems, which may result by upgrading
96 Installing the kernel source
97 ----------------------------
99 - If you install the full sources, put the kernel tarball in a
100 directory where you have permissions (e.g. your home directory) and
103 xz -cd linux-4.X.tar.xz | tar xvf -
105 Replace "X" with the version number of the latest kernel.
107 Do NOT use the /usr/src/linux area! This area has a (usually
108 incomplete) set of kernel headers that are used by the library header
109 files. They should match the library, and not get messed up by
110 whatever the kernel-du-jour happens to be.
112 - You can also upgrade between 4.x releases by patching. Patches are
113 distributed in the xz format. To install by patching, get all the
114 newer patch files, enter the top level directory of the kernel source
115 (linux-4.X) and execute::
117 xz -cd ../patch-4.x.xz | patch -p1
119 Replace "x" for all versions bigger than the version "X" of your current
120 source tree, **in_order**, and you should be ok. You may want to remove
121 the backup files (some-file-name~ or some-file-name.orig), and make sure
122 that there are no failed patches (some-file-name# or some-file-name.rej).
123 If there are, either you or I have made a mistake.
125 Unlike patches for the 4.x kernels, patches for the 4.x.y kernels
126 (also known as the -stable kernels) are not incremental but instead apply
127 directly to the base 4.x kernel. For example, if your base kernel is 4.0
128 and you want to apply the 4.0.3 patch, you must not first apply the 4.0.1
129 and 4.0.2 patches. Similarly, if you are running kernel version 4.0.2 and
130 want to jump to 4.0.3, you must first reverse the 4.0.2 patch (that is,
131 patch -R) **before** applying the 4.0.3 patch. You can read more on this in
132 :ref:`Documentation/process/applying-patches.rst <applying_patches>`.
134 Alternatively, the script patch-kernel can be used to automate this
135 process. It determines the current kernel version and applies any
138 linux/scripts/patch-kernel linux
140 The first argument in the command above is the location of the
141 kernel source. Patches are applied from the current directory, but
142 an alternative directory can be specified as the second argument.
144 - Make sure you have no stale .o files and dependencies lying around::
149 You should now have the sources correctly installed.
151 Software requirements
152 ---------------------
154 Compiling and running the 4.x kernels requires up-to-date
155 versions of various software packages. Consult
156 :ref:`Documentation/process/changes.rst <changes>` for the minimum version numbers
157 required and how to get updates for these packages. Beware that using
158 excessively old versions of these packages can cause indirect
159 errors that are very difficult to track down, so don't assume that
160 you can just update packages when obvious problems arise during
163 Build directory for the kernel
164 ------------------------------
166 When compiling the kernel, all output files will per default be
167 stored together with the kernel source code.
168 Using the option ``make O=output/dir`` allows you to specify an alternate
169 place for the output files (including .config).
172 kernel source code: /usr/src/linux-4.X
173 build directory: /home/name/build/kernel
175 To configure and build the kernel, use::
177 cd /usr/src/linux-4.X
178 make O=/home/name/build/kernel menuconfig
179 make O=/home/name/build/kernel
180 sudo make O=/home/name/build/kernel modules_install install
182 Please note: If the ``O=output/dir`` option is used, then it must be
183 used for all invocations of make.
185 Configuring the kernel
186 ----------------------
188 Do not skip this step even if you are only upgrading one minor
189 version. New configuration options are added in each release, and
190 odd problems will turn up if the configuration files are not set up
191 as expected. If you want to carry your existing configuration to a
192 new version with minimal work, use ``make oldconfig``, which will
193 only ask you for the answers to new questions.
195 - Alternative configuration commands are::
197 "make config" Plain text interface.
199 "make menuconfig" Text based color menus, radiolists & dialogs.
201 "make nconfig" Enhanced text based color menus.
203 "make xconfig" Qt based configuration tool.
205 "make gconfig" GTK+ based configuration tool.
207 "make oldconfig" Default all questions based on the contents of
208 your existing ./.config file and asking about
211 "make silentoldconfig"
212 Like above, but avoids cluttering the screen
213 with questions already answered.
214 Additionally updates the dependencies.
217 Like above, but sets new symbols to their default
218 values without prompting.
220 "make defconfig" Create a ./.config file by using the default
221 symbol values from either arch/$ARCH/defconfig
222 or arch/$ARCH/configs/${PLATFORM}_defconfig,
223 depending on the architecture.
225 "make ${PLATFORM}_defconfig"
226 Create a ./.config file by using the default
228 arch/$ARCH/configs/${PLATFORM}_defconfig.
229 Use "make help" to get a list of all available
230 platforms of your architecture.
233 Create a ./.config file by setting symbol
234 values to 'y' as much as possible.
237 Create a ./.config file by setting symbol
238 values to 'm' as much as possible.
240 "make allnoconfig" Create a ./.config file by setting symbol
241 values to 'n' as much as possible.
243 "make randconfig" Create a ./.config file by setting symbol
244 values to random values.
246 "make localmodconfig" Create a config based on current config and
247 loaded modules (lsmod). Disables any module
248 option that is not needed for the loaded modules.
250 To create a localmodconfig for another machine,
251 store the lsmod of that machine into a file
252 and pass it in as a LSMOD parameter.
254 target$ lsmod > /tmp/mylsmod
255 target$ scp /tmp/mylsmod host:/tmp
257 host$ make LSMOD=/tmp/mylsmod localmodconfig
259 The above also works when cross compiling.
261 "make localyesconfig" Similar to localmodconfig, except it will convert
262 all module options to built in (=y) options.
264 You can find more information on using the Linux kernel config tools
265 in Documentation/kbuild/kconfig.txt.
267 - NOTES on ``make config``:
269 - Having unnecessary drivers will make the kernel bigger, and can
270 under some circumstances lead to problems: probing for a
271 nonexistent controller card may confuse your other controllers.
273 - A kernel with math-emulation compiled in will still use the
274 coprocessor if one is present: the math emulation will just
275 never get used in that case. The kernel will be slightly larger,
276 but will work on different machines regardless of whether they
277 have a math coprocessor or not.
279 - The "kernel hacking" configuration details usually result in a
280 bigger or slower kernel (or both), and can even make the kernel
281 less stable by configuring some routines to actively try to
282 break bad code to find kernel problems (kmalloc()). Thus you
283 should probably answer 'n' to the questions for "development",
284 "experimental", or "debugging" features.
289 - Make sure you have at least gcc 3.2 available.
290 For more information, refer to :ref:`Documentation/process/changes.rst <changes>`.
292 Please note that you can still run a.out user programs with this kernel.
294 - Do a ``make`` to create a compressed kernel image. It is also
295 possible to do ``make install`` if you have lilo installed to suit the
296 kernel makefiles, but you may want to check your particular lilo setup first.
298 To do the actual install, you have to be root, but none of the normal
299 build should require that. Don't take the name of root in vain.
301 - If you configured any of the parts of the kernel as ``modules``, you
302 will also have to do ``make modules_install``.
304 - Verbose kernel compile/build output:
306 Normally, the kernel build system runs in a fairly quiet mode (but not
307 totally silent). However, sometimes you or other kernel developers need
308 to see compile, link, or other commands exactly as they are executed.
309 For this, use "verbose" build mode. This is done by passing
310 ``V=1`` to the ``make`` command, e.g.::
314 To have the build system also tell the reason for the rebuild of each
315 target, use ``V=2``. The default is ``V=0``.
317 - Keep a backup kernel handy in case something goes wrong. This is
318 especially true for the development releases, since each new release
319 contains new code which has not been debugged. Make sure you keep a
320 backup of the modules corresponding to that kernel, as well. If you
321 are installing a new kernel with the same version number as your
322 working kernel, make a backup of your modules directory before you
323 do a ``make modules_install``.
325 Alternatively, before compiling, use the kernel config option
326 "LOCALVERSION" to append a unique suffix to the regular kernel version.
327 LOCALVERSION can be set in the "General Setup" menu.
329 - In order to boot your new kernel, you'll need to copy the kernel
330 image (e.g. .../linux/arch/x86/boot/bzImage after compilation)
331 to the place where your regular bootable kernel is found.
333 - Booting a kernel directly from a floppy without the assistance of a
334 bootloader such as LILO, is no longer supported.
336 If you boot Linux from the hard drive, chances are you use LILO, which
337 uses the kernel image as specified in the file /etc/lilo.conf. The
338 kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or
339 /boot/bzImage. To use the new kernel, save a copy of the old image
340 and copy the new image over the old one. Then, you MUST RERUN LILO
341 to update the loading map! If you don't, you won't be able to boot
342 the new kernel image.
344 Reinstalling LILO is usually a matter of running /sbin/lilo.
345 You may wish to edit /etc/lilo.conf to specify an entry for your
346 old kernel image (say, /vmlinux.old) in case the new one does not
347 work. See the LILO docs for more information.
349 After reinstalling LILO, you should be all set. Shutdown the system,
352 If you ever need to change the default root device, video mode,
353 ramdisk size, etc. in the kernel image, use the ``rdev`` program (or
354 alternatively the LILO boot options when appropriate). No need to
355 recompile the kernel to change these parameters.
357 - Reboot with the new kernel and enjoy.
359 If something goes wrong
360 -----------------------
362 - If you have problems that seem to be due to kernel bugs, please check
363 the file MAINTAINERS to see if there is a particular person associated
364 with the part of the kernel that you are having trouble with. If there
365 isn't anyone listed there, then the second best thing is to mail
366 them to me (torvalds@linux-foundation.org), and possibly to any other
367 relevant mailing-list or to the newsgroup.
369 - In all bug-reports, *please* tell what kernel you are talking about,
370 how to duplicate the problem, and what your setup is (use your common
371 sense). If the problem is new, tell me so, and if the problem is
372 old, please try to tell me when you first noticed it.
374 - If the bug results in a message like::
376 unable to handle kernel paging request at address C0000010
379 eax: xxxxxxxx ebx: xxxxxxxx ecx: xxxxxxxx edx: xxxxxxxx
380 esi: xxxxxxxx edi: xxxxxxxx ebp: xxxxxxxx
381 ds: xxxx es: xxxx fs: xxxx gs: xxxx
382 Pid: xx, process nr: xx
383 xx xx xx xx xx xx xx xx xx xx
385 or similar kernel debugging information on your screen or in your
386 system log, please duplicate it *exactly*. The dump may look
387 incomprehensible to you, but it does contain information that may
388 help debugging the problem. The text above the dump is also
389 important: it tells something about why the kernel dumped code (in
390 the above example, it's due to a bad kernel pointer). More information
391 on making sense of the dump is in Documentation/admin-guide/oops-tracing.rst
393 - If you compiled the kernel with CONFIG_KALLSYMS you can send the dump
394 as is, otherwise you will have to use the ``ksymoops`` program to make
395 sense of the dump (but compiling with CONFIG_KALLSYMS is usually preferred).
396 This utility can be downloaded from
397 https://www.kernel.org/pub/linux/utils/kernel/ksymoops/ .
398 Alternatively, you can do the dump lookup by hand:
400 - In debugging dumps like the above, it helps enormously if you can
401 look up what the EIP value means. The hex value as such doesn't help
402 me or anybody else very much: it will depend on your particular
403 kernel setup. What you should do is take the hex value from the EIP
404 line (ignore the ``0010:``), and look it up in the kernel namelist to
405 see which kernel function contains the offending address.
407 To find out the kernel function name, you'll need to find the system
408 binary associated with the kernel that exhibited the symptom. This is
409 the file 'linux/vmlinux'. To extract the namelist and match it against
410 the EIP from the kernel crash, do::
412 nm vmlinux | sort | less
414 This will give you a list of kernel addresses sorted in ascending
415 order, from which it is simple to find the function that contains the
416 offending address. Note that the address given by the kernel
417 debugging messages will not necessarily match exactly with the
418 function addresses (in fact, that is very unlikely), so you can't
419 just 'grep' the list: the list will, however, give you the starting
420 point of each kernel function, so by looking for the function that
421 has a starting address lower than the one you are searching for but
422 is followed by a function with a higher address you will find the one
423 you want. In fact, it may be a good idea to include a bit of
424 "context" in your problem report, giving a few lines around the
427 If you for some reason cannot do the above (you have a pre-compiled
428 kernel image or similar), telling me as much about your setup as
429 possible will help. Please read the :ref:`admin-guide/reporting-bugs.rst <reportingbugs>`
430 document for details.
432 - Alternatively, you can use gdb on a running kernel. (read-only; i.e. you
433 cannot change values or set break points.) To do this, first compile the
434 kernel with -g; edit arch/x86/Makefile appropriately, then do a ``make
435 clean``. You'll also need to enable CONFIG_PROC_FS (via ``make config``).
437 After you've rebooted with the new kernel, do ``gdb vmlinux /proc/kcore``.
438 You can now use all the usual gdb commands. The command to look up the
439 point where your system crashed is ``l *0xXXXXXXXX``. (Replace the XXXes
442 gdb'ing a non-running kernel currently fails because ``gdb`` (wrongly)
443 disregards the starting offset for which the kernel is compiled.