1 Linux kernel release 4.x <http://kernel.org/>
2 =============================================
4 These are the release notes for Linux version 4. 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.
11 Linux is a clone of the operating system Unix, written from scratch by
12 Linus Torvalds with assistance from a loosely-knit team of hackers across
13 the Net. It aims towards POSIX and Single UNIX Specification compliance.
15 It has all the features you would expect in a modern fully-fledged Unix,
16 including true multitasking, virtual memory, shared libraries, demand
17 loading, shared copy-on-write executables, proper memory management,
18 and multistack networking including IPv4 and IPv6.
20 It is distributed under the GNU General Public License - see the
21 accompanying COPYING file for more details.
23 On what hardware does it run?
24 -----------------------------
26 Although originally developed first for 32-bit x86-based PCs (386 or higher),
27 today Linux also runs on (at least) the Compaq Alpha AXP, Sun SPARC and
28 UltraSPARC, Motorola 68000, PowerPC, PowerPC64, ARM, Hitachi SuperH, Cell,
29 IBM S/390, MIPS, HP PA-RISC, Intel IA-64, DEC VAX, AMD x86-64, AXIS CRIS,
30 Xtensa, Tilera TILE, AVR32, ARC and Renesas M32R architectures.
32 Linux is easily portable to most general-purpose 32- or 64-bit architectures
33 as long as they have a paged memory management unit (PMMU) and a port of the
34 GNU C compiler (gcc) (part of The GNU Compiler Collection, GCC). Linux has
35 also been ported to a number of architectures without a PMMU, although
36 functionality is then obviously somewhat limited.
37 Linux has also been ported to itself. You can now run the kernel as a
38 userspace application - this is called UserMode Linux (UML).
43 - There is a lot of documentation available both in electronic form on
44 the Internet and in books, both Linux-specific and pertaining to
45 general UNIX questions. I'd recommend looking into the documentation
46 subdirectories on any Linux FTP site for the LDP (Linux Documentation
47 Project) books. This README is not meant to be documentation on the
48 system: there are much better sources available.
50 - There are various README files in the Documentation/ subdirectory:
51 these typically contain kernel-specific installation notes for some
52 drivers for example. See Documentation/00-INDEX for a list of what
53 is contained in each file. Please read the Changes file, as it
54 contains information about the problems, which may result by upgrading
57 - The Documentation/DocBook/ subdirectory contains several guides for
58 kernel developers and users. These guides can be rendered in a
59 number of formats: PostScript (.ps), PDF, HTML, & man-pages, among others.
60 After installation, ``make psdocs``, ``make pdfdocs``, ``make htmldocs``,
61 or ``make mandocs`` will render the documentation in the requested format.
63 Installing the kernel source
64 ----------------------------
66 - If you install the full sources, put the kernel tarball in a
67 directory where you have permissions (e.g. your home directory) and
70 xz -cd linux-4.X.tar.xz | tar xvf -
72 Replace "X" with the version number of the latest kernel.
74 Do NOT use the /usr/src/linux area! This area has a (usually
75 incomplete) set of kernel headers that are used by the library header
76 files. They should match the library, and not get messed up by
77 whatever the kernel-du-jour happens to be.
79 - You can also upgrade between 4.x releases by patching. Patches are
80 distributed in the xz format. To install by patching, get all the
81 newer patch files, enter the top level directory of the kernel source
82 (linux-4.X) and execute::
84 xz -cd ../patch-4.x.xz | patch -p1
86 Replace "x" for all versions bigger than the version "X" of your current
87 source tree, **in_order**, and you should be ok. You may want to remove
88 the backup files (some-file-name~ or some-file-name.orig), and make sure
89 that there are no failed patches (some-file-name# or some-file-name.rej).
90 If there are, either you or I have made a mistake.
92 Unlike patches for the 4.x kernels, patches for the 4.x.y kernels
93 (also known as the -stable kernels) are not incremental but instead apply
94 directly to the base 4.x kernel. For example, if your base kernel is 4.0
95 and you want to apply the 4.0.3 patch, you must not first apply the 4.0.1
96 and 4.0.2 patches. Similarly, if you are running kernel version 4.0.2 and
97 want to jump to 4.0.3, you must first reverse the 4.0.2 patch (that is,
98 patch -R) **before** applying the 4.0.3 patch. You can read more on this in
99 :ref:`Documentation/applying-patches.txt <applying_patches>`.
101 Alternatively, the script patch-kernel can be used to automate this
102 process. It determines the current kernel version and applies any
105 linux/scripts/patch-kernel linux
107 The first argument in the command above is the location of the
108 kernel source. Patches are applied from the current directory, but
109 an alternative directory can be specified as the second argument.
111 - Make sure you have no stale .o files and dependencies lying around::
116 You should now have the sources correctly installed.
118 Software requirements
119 ---------------------
121 Compiling and running the 4.x kernels requires up-to-date
122 versions of various software packages. Consult
123 :ref:`Documentation/Changes <changes>` for the minimum version numbers
124 required and how to get updates for these packages. Beware that using
125 excessively old versions of these packages can cause indirect
126 errors that are very difficult to track down, so don't assume that
127 you can just update packages when obvious problems arise during
130 Build directory for the kernel
131 ------------------------------
133 When compiling the kernel, all output files will per default be
134 stored together with the kernel source code.
135 Using the option ``make O=output/dir`` allows you to specify an alternate
136 place for the output files (including .config).
139 kernel source code: /usr/src/linux-4.X
140 build directory: /home/name/build/kernel
142 To configure and build the kernel, use::
144 cd /usr/src/linux-4.X
145 make O=/home/name/build/kernel menuconfig
146 make O=/home/name/build/kernel
147 sudo make O=/home/name/build/kernel modules_install install
149 Please note: If the ``O=output/dir`` option is used, then it must be
150 used for all invocations of make.
152 Configuring the kernel
153 ----------------------
155 Do not skip this step even if you are only upgrading one minor
156 version. New configuration options are added in each release, and
157 odd problems will turn up if the configuration files are not set up
158 as expected. If you want to carry your existing configuration to a
159 new version with minimal work, use ``make oldconfig``, which will
160 only ask you for the answers to new questions.
162 - Alternative configuration commands are::
164 "make config" Plain text interface.
166 "make menuconfig" Text based color menus, radiolists & dialogs.
168 "make nconfig" Enhanced text based color menus.
170 "make xconfig" Qt based configuration tool.
172 "make gconfig" GTK+ based configuration tool.
174 "make oldconfig" Default all questions based on the contents of
175 your existing ./.config file and asking about
178 "make silentoldconfig"
179 Like above, but avoids cluttering the screen
180 with questions already answered.
181 Additionally updates the dependencies.
184 Like above, but sets new symbols to their default
185 values without prompting.
187 "make defconfig" Create a ./.config file by using the default
188 symbol values from either arch/$ARCH/defconfig
189 or arch/$ARCH/configs/${PLATFORM}_defconfig,
190 depending on the architecture.
192 "make ${PLATFORM}_defconfig"
193 Create a ./.config file by using the default
195 arch/$ARCH/configs/${PLATFORM}_defconfig.
196 Use "make help" to get a list of all available
197 platforms of your architecture.
200 Create a ./.config file by setting symbol
201 values to 'y' as much as possible.
204 Create a ./.config file by setting symbol
205 values to 'm' as much as possible.
207 "make allnoconfig" Create a ./.config file by setting symbol
208 values to 'n' as much as possible.
210 "make randconfig" Create a ./.config file by setting symbol
211 values to random values.
213 "make localmodconfig" Create a config based on current config and
214 loaded modules (lsmod). Disables any module
215 option that is not needed for the loaded modules.
217 To create a localmodconfig for another machine,
218 store the lsmod of that machine into a file
219 and pass it in as a LSMOD parameter.
221 target$ lsmod > /tmp/mylsmod
222 target$ scp /tmp/mylsmod host:/tmp
224 host$ make LSMOD=/tmp/mylsmod localmodconfig
226 The above also works when cross compiling.
228 "make localyesconfig" Similar to localmodconfig, except it will convert
229 all module options to built in (=y) options.
231 You can find more information on using the Linux kernel config tools
232 in Documentation/kbuild/kconfig.txt.
234 - NOTES on ``make config``:
236 - Having unnecessary drivers will make the kernel bigger, and can
237 under some circumstances lead to problems: probing for a
238 nonexistent controller card may confuse your other controllers
240 - A kernel with math-emulation compiled in will still use the
241 coprocessor if one is present: the math emulation will just
242 never get used in that case. The kernel will be slightly larger,
243 but will work on different machines regardless of whether they
244 have a math coprocessor or not.
246 - The "kernel hacking" configuration details usually result in a
247 bigger or slower kernel (or both), and can even make the kernel
248 less stable by configuring some routines to actively try to
249 break bad code to find kernel problems (kmalloc()). Thus you
250 should probably answer 'n' to the questions for "development",
251 "experimental", or "debugging" features.
256 - Make sure you have at least gcc 3.2 available.
257 For more information, refer to :ref:`Documentation/Changes <changes>`.
259 Please note that you can still run a.out user programs with this kernel.
261 - Do a ``make`` to create a compressed kernel image. It is also
262 possible to do ``make install`` if you have lilo installed to suit the
263 kernel makefiles, but you may want to check your particular lilo setup first.
265 To do the actual install, you have to be root, but none of the normal
266 build should require that. Don't take the name of root in vain.
268 - If you configured any of the parts of the kernel as ``modules``, you
269 will also have to do ``make modules_install``.
271 - Verbose kernel compile/build output:
273 Normally, the kernel build system runs in a fairly quiet mode (but not
274 totally silent). However, sometimes you or other kernel developers need
275 to see compile, link, or other commands exactly as they are executed.
276 For this, use "verbose" build mode. This is done by passing
277 ``V=1`` to the ``make`` command, e.g.::
281 To have the build system also tell the reason for the rebuild of each
282 target, use ``V=2``. The default is ``V=0``.
284 - Keep a backup kernel handy in case something goes wrong. This is
285 especially true for the development releases, since each new release
286 contains new code which has not been debugged. Make sure you keep a
287 backup of the modules corresponding to that kernel, as well. If you
288 are installing a new kernel with the same version number as your
289 working kernel, make a backup of your modules directory before you
290 do a ``make modules_install``.
292 Alternatively, before compiling, use the kernel config option
293 "LOCALVERSION" to append a unique suffix to the regular kernel version.
294 LOCALVERSION can be set in the "General Setup" menu.
296 - In order to boot your new kernel, you'll need to copy the kernel
297 image (e.g. .../linux/arch/x86/boot/bzImage after compilation)
298 to the place where your regular bootable kernel is found.
300 - Booting a kernel directly from a floppy without the assistance of a
301 bootloader such as LILO, is no longer supported.
303 If you boot Linux from the hard drive, chances are you use LILO, which
304 uses the kernel image as specified in the file /etc/lilo.conf. The
305 kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or
306 /boot/bzImage. To use the new kernel, save a copy of the old image
307 and copy the new image over the old one. Then, you MUST RERUN LILO
308 to update the loading map! If you don't, you won't be able to boot
309 the new kernel image.
311 Reinstalling LILO is usually a matter of running /sbin/lilo.
312 You may wish to edit /etc/lilo.conf to specify an entry for your
313 old kernel image (say, /vmlinux.old) in case the new one does not
314 work. See the LILO docs for more information.
316 After reinstalling LILO, you should be all set. Shutdown the system,
319 If you ever need to change the default root device, video mode,
320 ramdisk size, etc. in the kernel image, use the ``rdev`` program (or
321 alternatively the LILO boot options when appropriate). No need to
322 recompile the kernel to change these parameters.
324 - Reboot with the new kernel and enjoy.
326 If something goes wrong
327 -----------------------
329 - If you have problems that seem to be due to kernel bugs, please check
330 the file MAINTAINERS to see if there is a particular person associated
331 with the part of the kernel that you are having trouble with. If there
332 isn't anyone listed there, then the second best thing is to mail
333 them to me (torvalds@linux-foundation.org), and possibly to any other
334 relevant mailing-list or to the newsgroup.
336 - In all bug-reports, *please* tell what kernel you are talking about,
337 how to duplicate the problem, and what your setup is (use your common
338 sense). If the problem is new, tell me so, and if the problem is
339 old, please try to tell me when you first noticed it.
341 - If the bug results in a message like::
343 unable to handle kernel paging request at address C0000010
346 eax: xxxxxxxx ebx: xxxxxxxx ecx: xxxxxxxx edx: xxxxxxxx
347 esi: xxxxxxxx edi: xxxxxxxx ebp: xxxxxxxx
348 ds: xxxx es: xxxx fs: xxxx gs: xxxx
349 Pid: xx, process nr: xx
350 xx xx xx xx xx xx xx xx xx xx
352 or similar kernel debugging information on your screen or in your
353 system log, please duplicate it *exactly*. The dump may look
354 incomprehensible to you, but it does contain information that may
355 help debugging the problem. The text above the dump is also
356 important: it tells something about why the kernel dumped code (in
357 the above example, it's due to a bad kernel pointer). More information
358 on making sense of the dump is in Documentation/oops-tracing.txt
360 - If you compiled the kernel with CONFIG_KALLSYMS you can send the dump
361 as is, otherwise you will have to use the ``ksymoops`` program to make
362 sense of the dump (but compiling with CONFIG_KALLSYMS is usually preferred).
363 This utility can be downloaded from
364 ftp://ftp.<country>.kernel.org/pub/linux/utils/kernel/ksymoops/ .
365 Alternatively, you can do the dump lookup by hand:
367 - In debugging dumps like the above, it helps enormously if you can
368 look up what the EIP value means. The hex value as such doesn't help
369 me or anybody else very much: it will depend on your particular
370 kernel setup. What you should do is take the hex value from the EIP
371 line (ignore the ``0010:``), and look it up in the kernel namelist to
372 see which kernel function contains the offending address.
374 To find out the kernel function name, you'll need to find the system
375 binary associated with the kernel that exhibited the symptom. This is
376 the file 'linux/vmlinux'. To extract the namelist and match it against
377 the EIP from the kernel crash, do::
379 nm vmlinux | sort | less
381 This will give you a list of kernel addresses sorted in ascending
382 order, from which it is simple to find the function that contains the
383 offending address. Note that the address given by the kernel
384 debugging messages will not necessarily match exactly with the
385 function addresses (in fact, that is very unlikely), so you can't
386 just 'grep' the list: the list will, however, give you the starting
387 point of each kernel function, so by looking for the function that
388 has a starting address lower than the one you are searching for but
389 is followed by a function with a higher address you will find the one
390 you want. In fact, it may be a good idea to include a bit of
391 "context" in your problem report, giving a few lines around the
394 If you for some reason cannot do the above (you have a pre-compiled
395 kernel image or similar), telling me as much about your setup as
396 possible will help. Please read the :ref:`REPORTING-BUGS <reportingbugs>`
397 document for details.
399 - Alternatively, you can use gdb on a running kernel. (read-only; i.e. you
400 cannot change values or set break points.) To do this, first compile the
401 kernel with -g; edit arch/x86/Makefile appropriately, then do a ``make
402 clean``. You'll also need to enable CONFIG_PROC_FS (via ``make config``).
404 After you've rebooted with the new kernel, do ``gdb vmlinux /proc/kcore``.
405 You can now use all the usual gdb commands. The command to look up the
406 point where your system crashed is ``l *0xXXXXXXXX``. (Replace the XXXes
409 gdb'ing a non-running kernel currently fails because ``gdb`` (wrongly)
410 disregards the starting offset for which the kernel is compiled.
git.samba.org / sfrench / cifs-2.6.git / blob