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 v2 - 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, 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
54 :ref:`Documentation/process/changes.rst <changes>` file, as it
55 contains information about the problems, which may result by upgrading
58 Installing the kernel source
59 ----------------------------
61 - If you install the full sources, put the kernel tarball in a
62 directory where you have permissions (e.g. your home directory) and
65 xz -cd linux-4.X.tar.xz | tar xvf -
67 Replace "X" with the version number of the latest kernel.
69 Do NOT use the /usr/src/linux area! This area has a (usually
70 incomplete) set of kernel headers that are used by the library header
71 files. They should match the library, and not get messed up by
72 whatever the kernel-du-jour happens to be.
74 - You can also upgrade between 4.x releases by patching. Patches are
75 distributed in the xz format. To install by patching, get all the
76 newer patch files, enter the top level directory of the kernel source
77 (linux-4.X) and execute::
79 xz -cd ../patch-4.x.xz | patch -p1
81 Replace "x" for all versions bigger than the version "X" of your current
82 source tree, **in_order**, and you should be ok. You may want to remove
83 the backup files (some-file-name~ or some-file-name.orig), and make sure
84 that there are no failed patches (some-file-name# or some-file-name.rej).
85 If there are, either you or I have made a mistake.
87 Unlike patches for the 4.x kernels, patches for the 4.x.y kernels
88 (also known as the -stable kernels) are not incremental but instead apply
89 directly to the base 4.x kernel. For example, if your base kernel is 4.0
90 and you want to apply the 4.0.3 patch, you must not first apply the 4.0.1
91 and 4.0.2 patches. Similarly, if you are running kernel version 4.0.2 and
92 want to jump to 4.0.3, you must first reverse the 4.0.2 patch (that is,
93 patch -R) **before** applying the 4.0.3 patch. You can read more on this in
94 :ref:`Documentation/process/applying-patches.rst <applying_patches>`.
96 Alternatively, the script patch-kernel can be used to automate this
97 process. It determines the current kernel version and applies any
100 linux/scripts/patch-kernel linux
102 The first argument in the command above is the location of the
103 kernel source. Patches are applied from the current directory, but
104 an alternative directory can be specified as the second argument.
106 - Make sure you have no stale .o files and dependencies lying around::
111 You should now have the sources correctly installed.
113 Software requirements
114 ---------------------
116 Compiling and running the 4.x kernels requires up-to-date
117 versions of various software packages. Consult
118 :ref:`Documentation/process/changes.rst <changes>` for the minimum version numbers
119 required and how to get updates for these packages. Beware that using
120 excessively old versions of these packages can cause indirect
121 errors that are very difficult to track down, so don't assume that
122 you can just update packages when obvious problems arise during
125 Build directory for the kernel
126 ------------------------------
128 When compiling the kernel, all output files will per default be
129 stored together with the kernel source code.
130 Using the option ``make O=output/dir`` allows you to specify an alternate
131 place for the output files (including .config).
134 kernel source code: /usr/src/linux-4.X
135 build directory: /home/name/build/kernel
137 To configure and build the kernel, use::
139 cd /usr/src/linux-4.X
140 make O=/home/name/build/kernel menuconfig
141 make O=/home/name/build/kernel
142 sudo make O=/home/name/build/kernel modules_install install
144 Please note: If the ``O=output/dir`` option is used, then it must be
145 used for all invocations of make.
147 Configuring the kernel
148 ----------------------
150 Do not skip this step even if you are only upgrading one minor
151 version. New configuration options are added in each release, and
152 odd problems will turn up if the configuration files are not set up
153 as expected. If you want to carry your existing configuration to a
154 new version with minimal work, use ``make oldconfig``, which will
155 only ask you for the answers to new questions.
157 - Alternative configuration commands are::
159 "make config" Plain text interface.
161 "make menuconfig" Text based color menus, radiolists & dialogs.
163 "make nconfig" Enhanced text based color menus.
165 "make xconfig" Qt based configuration tool.
167 "make gconfig" GTK+ based configuration tool.
169 "make oldconfig" Default all questions based on the contents of
170 your existing ./.config file and asking about
173 "make silentoldconfig"
174 Like above, but avoids cluttering the screen
175 with questions already answered.
176 Additionally updates the dependencies.
179 Like above, but sets new symbols to their default
180 values without prompting.
182 "make defconfig" Create a ./.config file by using the default
183 symbol values from either arch/$ARCH/defconfig
184 or arch/$ARCH/configs/${PLATFORM}_defconfig,
185 depending on the architecture.
187 "make ${PLATFORM}_defconfig"
188 Create a ./.config file by using the default
190 arch/$ARCH/configs/${PLATFORM}_defconfig.
191 Use "make help" to get a list of all available
192 platforms of your architecture.
195 Create a ./.config file by setting symbol
196 values to 'y' as much as possible.
199 Create a ./.config file by setting symbol
200 values to 'm' as much as possible.
202 "make allnoconfig" Create a ./.config file by setting symbol
203 values to 'n' as much as possible.
205 "make randconfig" Create a ./.config file by setting symbol
206 values to random values.
208 "make localmodconfig" Create a config based on current config and
209 loaded modules (lsmod). Disables any module
210 option that is not needed for the loaded modules.
212 To create a localmodconfig for another machine,
213 store the lsmod of that machine into a file
214 and pass it in as a LSMOD parameter.
216 target$ lsmod > /tmp/mylsmod
217 target$ scp /tmp/mylsmod host:/tmp
219 host$ make LSMOD=/tmp/mylsmod localmodconfig
221 The above also works when cross compiling.
223 "make localyesconfig" Similar to localmodconfig, except it will convert
224 all module options to built in (=y) options.
226 You can find more information on using the Linux kernel config tools
227 in Documentation/kbuild/kconfig.txt.
229 - NOTES on ``make config``:
231 - Having unnecessary drivers will make the kernel bigger, and can
232 under some circumstances lead to problems: probing for a
233 nonexistent controller card may confuse your other controllers.
235 - A kernel with math-emulation compiled in will still use the
236 coprocessor if one is present: the math emulation will just
237 never get used in that case. The kernel will be slightly larger,
238 but will work on different machines regardless of whether they
239 have a math coprocessor or not.
241 - The "kernel hacking" configuration details usually result in a
242 bigger or slower kernel (or both), and can even make the kernel
243 less stable by configuring some routines to actively try to
244 break bad code to find kernel problems (kmalloc()). Thus you
245 should probably answer 'n' to the questions for "development",
246 "experimental", or "debugging" features.
251 - Make sure you have at least gcc 3.2 available.
252 For more information, refer to :ref:`Documentation/process/changes.rst <changes>`.
254 Please note that you can still run a.out user programs with this kernel.
256 - Do a ``make`` to create a compressed kernel image. It is also
257 possible to do ``make install`` if you have lilo installed to suit the
258 kernel makefiles, but you may want to check your particular lilo setup first.
260 To do the actual install, you have to be root, but none of the normal
261 build should require that. Don't take the name of root in vain.
263 - If you configured any of the parts of the kernel as ``modules``, you
264 will also have to do ``make modules_install``.
266 - Verbose kernel compile/build output:
268 Normally, the kernel build system runs in a fairly quiet mode (but not
269 totally silent). However, sometimes you or other kernel developers need
270 to see compile, link, or other commands exactly as they are executed.
271 For this, use "verbose" build mode. This is done by passing
272 ``V=1`` to the ``make`` command, e.g.::
276 To have the build system also tell the reason for the rebuild of each
277 target, use ``V=2``. The default is ``V=0``.
279 - Keep a backup kernel handy in case something goes wrong. This is
280 especially true for the development releases, since each new release
281 contains new code which has not been debugged. Make sure you keep a
282 backup of the modules corresponding to that kernel, as well. If you
283 are installing a new kernel with the same version number as your
284 working kernel, make a backup of your modules directory before you
285 do a ``make modules_install``.
287 Alternatively, before compiling, use the kernel config option
288 "LOCALVERSION" to append a unique suffix to the regular kernel version.
289 LOCALVERSION can be set in the "General Setup" menu.
291 - In order to boot your new kernel, you'll need to copy the kernel
292 image (e.g. .../linux/arch/x86/boot/bzImage after compilation)
293 to the place where your regular bootable kernel is found.
295 - Booting a kernel directly from a floppy without the assistance of a
296 bootloader such as LILO, is no longer supported.
298 If you boot Linux from the hard drive, chances are you use LILO, which
299 uses the kernel image as specified in the file /etc/lilo.conf. The
300 kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or
301 /boot/bzImage. To use the new kernel, save a copy of the old image
302 and copy the new image over the old one. Then, you MUST RERUN LILO
303 to update the loading map! If you don't, you won't be able to boot
304 the new kernel image.
306 Reinstalling LILO is usually a matter of running /sbin/lilo.
307 You may wish to edit /etc/lilo.conf to specify an entry for your
308 old kernel image (say, /vmlinux.old) in case the new one does not
309 work. See the LILO docs for more information.
311 After reinstalling LILO, you should be all set. Shutdown the system,
314 If you ever need to change the default root device, video mode,
315 ramdisk size, etc. in the kernel image, use the ``rdev`` program (or
316 alternatively the LILO boot options when appropriate). No need to
317 recompile the kernel to change these parameters.
319 - Reboot with the new kernel and enjoy.
321 If something goes wrong
322 -----------------------
324 - If you have problems that seem to be due to kernel bugs, please check
325 the file MAINTAINERS to see if there is a particular person associated
326 with the part of the kernel that you are having trouble with. If there
327 isn't anyone listed there, then the second best thing is to mail
328 them to me (torvalds@linux-foundation.org), and possibly to any other
329 relevant mailing-list or to the newsgroup.
331 - In all bug-reports, *please* tell what kernel you are talking about,
332 how to duplicate the problem, and what your setup is (use your common
333 sense). If the problem is new, tell me so, and if the problem is
334 old, please try to tell me when you first noticed it.
336 - If the bug results in a message like::
338 unable to handle kernel paging request at address C0000010
341 eax: xxxxxxxx ebx: xxxxxxxx ecx: xxxxxxxx edx: xxxxxxxx
342 esi: xxxxxxxx edi: xxxxxxxx ebp: xxxxxxxx
343 ds: xxxx es: xxxx fs: xxxx gs: xxxx
344 Pid: xx, process nr: xx
345 xx xx xx xx xx xx xx xx xx xx
347 or similar kernel debugging information on your screen or in your
348 system log, please duplicate it *exactly*. The dump may look
349 incomprehensible to you, but it does contain information that may
350 help debugging the problem. The text above the dump is also
351 important: it tells something about why the kernel dumped code (in
352 the above example, it's due to a bad kernel pointer). More information
353 on making sense of the dump is in Documentation/admin-guide/bug-hunting.rst
355 - If you compiled the kernel with CONFIG_KALLSYMS you can send the dump
356 as is, otherwise you will have to use the ``ksymoops`` program to make
357 sense of the dump (but compiling with CONFIG_KALLSYMS is usually preferred).
358 This utility can be downloaded from
359 https://www.kernel.org/pub/linux/utils/kernel/ksymoops/ .
360 Alternatively, you can do the dump lookup by hand:
362 - In debugging dumps like the above, it helps enormously if you can
363 look up what the EIP value means. The hex value as such doesn't help
364 me or anybody else very much: it will depend on your particular
365 kernel setup. What you should do is take the hex value from the EIP
366 line (ignore the ``0010:``), and look it up in the kernel namelist to
367 see which kernel function contains the offending address.
369 To find out the kernel function name, you'll need to find the system
370 binary associated with the kernel that exhibited the symptom. This is
371 the file 'linux/vmlinux'. To extract the namelist and match it against
372 the EIP from the kernel crash, do::
374 nm vmlinux | sort | less
376 This will give you a list of kernel addresses sorted in ascending
377 order, from which it is simple to find the function that contains the
378 offending address. Note that the address given by the kernel
379 debugging messages will not necessarily match exactly with the
380 function addresses (in fact, that is very unlikely), so you can't
381 just 'grep' the list: the list will, however, give you the starting
382 point of each kernel function, so by looking for the function that
383 has a starting address lower than the one you are searching for but
384 is followed by a function with a higher address you will find the one
385 you want. In fact, it may be a good idea to include a bit of
386 "context" in your problem report, giving a few lines around the
389 If you for some reason cannot do the above (you have a pre-compiled
390 kernel image or similar), telling me as much about your setup as
391 possible will help. Please read the :ref:`admin-guide/reporting-bugs.rst <reportingbugs>`
392 document for details.
394 - Alternatively, you can use gdb on a running kernel. (read-only; i.e. you
395 cannot change values or set break points.) To do this, first compile the
396 kernel with -g; edit arch/x86/Makefile appropriately, then do a ``make
397 clean``. You'll also need to enable CONFIG_PROC_FS (via ``make config``).
399 After you've rebooted with the new kernel, do ``gdb vmlinux /proc/kcore``.
400 You can now use all the usual gdb commands. The command to look up the
401 point where your system crashed is ``l *0xXXXXXXXX``. (Replace the XXXes
404 gdb'ing a non-running kernel currently fails because ``gdb`` (wrongly)
405 disregards the starting offset for which the kernel is compiled.
git.samba.org / sfrench / cifs-2.6.git / blob