3 Linux kernel release 5.x <http://kernel.org/>
4 =============================================
6 These are the release notes for Linux version 5. Read them carefully,
7 as they tell you what this is all about, explain how to install the
8 kernel, and what to do if something goes wrong.
13 Linux is a clone of the operating system Unix, written from scratch by
14 Linus Torvalds with assistance from a loosely-knit team of hackers across
15 the Net. It aims towards POSIX and Single UNIX Specification compliance.
17 It has all the features you would expect in a modern fully-fledged Unix,
18 including true multitasking, virtual memory, shared libraries, demand
19 loading, shared copy-on-write executables, proper memory management,
20 and multistack networking including IPv4 and IPv6.
22 It is distributed under the GNU General Public License v2 - see the
23 accompanying COPYING file for more details.
25 On what hardware does it run?
26 -----------------------------
28 Although originally developed first for 32-bit x86-based PCs (386 or higher),
29 today Linux also runs on (at least) the Compaq Alpha AXP, Sun SPARC and
30 UltraSPARC, Motorola 68000, PowerPC, PowerPC64, ARM, Hitachi SuperH, Cell,
31 IBM S/390, MIPS, HP PA-RISC, Intel IA-64, DEC VAX, AMD x86-64 Xtensa, and
34 Linux is easily portable to most general-purpose 32- or 64-bit architectures
35 as long as they have a paged memory management unit (PMMU) and a port of the
36 GNU C compiler (gcc) (part of The GNU Compiler Collection, GCC). Linux has
37 also been ported to a number of architectures without a PMMU, although
38 functionality is then obviously somewhat limited.
39 Linux has also been ported to itself. You can now run the kernel as a
40 userspace application - this is called UserMode Linux (UML).
45 - There is a lot of documentation available both in electronic form on
46 the Internet and in books, both Linux-specific and pertaining to
47 general UNIX questions. I'd recommend looking into the documentation
48 subdirectories on any Linux FTP site for the LDP (Linux Documentation
49 Project) books. This README is not meant to be documentation on the
50 system: there are much better sources available.
52 - There are various README files in the Documentation/ subdirectory:
53 these typically contain kernel-specific installation notes for some
54 drivers for example. Please read the
55 :ref:`Documentation/process/changes.rst <changes>` file, as it
56 contains information about the problems, which may result by upgrading
59 Installing the kernel source
60 ----------------------------
62 - If you install the full sources, put the kernel tarball in a
63 directory where you have permissions (e.g. your home directory) and
66 xz -cd linux-5.x.tar.xz | tar xvf -
68 Replace "X" with the version number of the latest kernel.
70 Do NOT use the /usr/src/linux area! This area has a (usually
71 incomplete) set of kernel headers that are used by the library header
72 files. They should match the library, and not get messed up by
73 whatever the kernel-du-jour happens to be.
75 - You can also upgrade between 5.x releases by patching. Patches are
76 distributed in the xz format. To install by patching, get all the
77 newer patch files, enter the top level directory of the kernel source
78 (linux-5.x) and execute::
80 xz -cd ../patch-5.x.xz | patch -p1
82 Replace "x" for all versions bigger than the version "x" of your current
83 source tree, **in_order**, and you should be ok. You may want to remove
84 the backup files (some-file-name~ or some-file-name.orig), and make sure
85 that there are no failed patches (some-file-name# or some-file-name.rej).
86 If there are, either you or I have made a mistake.
88 Unlike patches for the 5.x kernels, patches for the 5.x.y kernels
89 (also known as the -stable kernels) are not incremental but instead apply
90 directly to the base 5.x kernel. For example, if your base kernel is 5.0
91 and you want to apply the 5.0.3 patch, you must not first apply the 5.0.1
92 and 5.0.2 patches. Similarly, if you are running kernel version 5.0.2 and
93 want to jump to 5.0.3, you must first reverse the 5.0.2 patch (that is,
94 patch -R) **before** applying the 5.0.3 patch. You can read more on this in
95 :ref:`Documentation/process/applying-patches.rst <applying_patches>`.
97 Alternatively, the script patch-kernel can be used to automate this
98 process. It determines the current kernel version and applies any
101 linux/scripts/patch-kernel linux
103 The first argument in the command above is the location of the
104 kernel source. Patches are applied from the current directory, but
105 an alternative directory can be specified as the second argument.
107 - Make sure you have no stale .o files and dependencies lying around::
112 You should now have the sources correctly installed.
114 Software requirements
115 ---------------------
117 Compiling and running the 5.x kernels requires up-to-date
118 versions of various software packages. Consult
119 :ref:`Documentation/process/changes.rst <changes>` for the minimum version numbers
120 required and how to get updates for these packages. Beware that using
121 excessively old versions of these packages can cause indirect
122 errors that are very difficult to track down, so don't assume that
123 you can just update packages when obvious problems arise during
126 Build directory for the kernel
127 ------------------------------
129 When compiling the kernel, all output files will per default be
130 stored together with the kernel source code.
131 Using the option ``make O=output/dir`` allows you to specify an alternate
132 place for the output files (including .config).
135 kernel source code: /usr/src/linux-5.x
136 build directory: /home/name/build/kernel
138 To configure and build the kernel, use::
140 cd /usr/src/linux-5.x
141 make O=/home/name/build/kernel menuconfig
142 make O=/home/name/build/kernel
143 sudo make O=/home/name/build/kernel modules_install install
145 Please note: If the ``O=output/dir`` option is used, then it must be
146 used for all invocations of make.
148 Configuring the kernel
149 ----------------------
151 Do not skip this step even if you are only upgrading one minor
152 version. New configuration options are added in each release, and
153 odd problems will turn up if the configuration files are not set up
154 as expected. If you want to carry your existing configuration to a
155 new version with minimal work, use ``make oldconfig``, which will
156 only ask you for the answers to new questions.
158 - Alternative configuration commands are::
160 "make config" Plain text interface.
162 "make menuconfig" Text based color menus, radiolists & dialogs.
164 "make nconfig" Enhanced text based color menus.
166 "make xconfig" Qt based configuration tool.
168 "make gconfig" GTK+ based configuration tool.
170 "make oldconfig" Default all questions based on the contents of
171 your existing ./.config file and asking about
175 Like above, but sets new symbols to their default
176 values without prompting.
178 "make defconfig" Create a ./.config file by using the default
179 symbol values from either arch/$ARCH/defconfig
180 or arch/$ARCH/configs/${PLATFORM}_defconfig,
181 depending on the architecture.
183 "make ${PLATFORM}_defconfig"
184 Create a ./.config file by using the default
186 arch/$ARCH/configs/${PLATFORM}_defconfig.
187 Use "make help" to get a list of all available
188 platforms of your architecture.
191 Create a ./.config file by setting symbol
192 values to 'y' as much as possible.
195 Create a ./.config file by setting symbol
196 values to 'm' as much as possible.
198 "make allnoconfig" Create a ./.config file by setting symbol
199 values to 'n' as much as possible.
201 "make randconfig" Create a ./.config file by setting symbol
202 values to random values.
204 "make localmodconfig" Create a config based on current config and
205 loaded modules (lsmod). Disables any module
206 option that is not needed for the loaded modules.
208 To create a localmodconfig for another machine,
209 store the lsmod of that machine into a file
210 and pass it in as a LSMOD parameter.
212 Also, you can preserve modules in certain folders
213 or kconfig files by specifying their paths in
216 target$ lsmod > /tmp/mylsmod
217 target$ scp /tmp/mylsmod host:/tmp
219 host$ make LSMOD=/tmp/mylsmod \
220 LMC_KEEP="drivers/usb:drivers/gpu:fs" \
223 The above also works when cross compiling.
225 "make localyesconfig" Similar to localmodconfig, except it will convert
226 all module options to built in (=y) options. You can
227 also preserve modules by LMC_KEEP.
229 "make kvmconfig" Enable additional options for kvm guest kernel support.
231 "make xenconfig" Enable additional options for xen dom0 guest kernel
234 "make tinyconfig" Configure the tiniest possible kernel.
236 You can find more information on using the Linux kernel config tools
237 in Documentation/kbuild/kconfig.rst.
239 - NOTES on ``make config``:
241 - Having unnecessary drivers will make the kernel bigger, and can
242 under some circumstances lead to problems: probing for a
243 nonexistent controller card may confuse your other controllers.
245 - A kernel with math-emulation compiled in will still use the
246 coprocessor if one is present: the math emulation will just
247 never get used in that case. The kernel will be slightly larger,
248 but will work on different machines regardless of whether they
249 have a math coprocessor or not.
251 - The "kernel hacking" configuration details usually result in a
252 bigger or slower kernel (or both), and can even make the kernel
253 less stable by configuring some routines to actively try to
254 break bad code to find kernel problems (kmalloc()). Thus you
255 should probably answer 'n' to the questions for "development",
256 "experimental", or "debugging" features.
261 - Make sure you have at least gcc 4.9 available.
262 For more information, refer to :ref:`Documentation/process/changes.rst <changes>`.
264 Please note that you can still run a.out user programs with this kernel.
266 - Do a ``make`` to create a compressed kernel image. It is also
267 possible to do ``make install`` if you have lilo installed to suit the
268 kernel makefiles, but you may want to check your particular lilo setup first.
270 To do the actual install, you have to be root, but none of the normal
271 build should require that. Don't take the name of root in vain.
273 - If you configured any of the parts of the kernel as ``modules``, you
274 will also have to do ``make modules_install``.
276 - Verbose kernel compile/build output:
278 Normally, the kernel build system runs in a fairly quiet mode (but not
279 totally silent). However, sometimes you or other kernel developers need
280 to see compile, link, or other commands exactly as they are executed.
281 For this, use "verbose" build mode. This is done by passing
282 ``V=1`` to the ``make`` command, e.g.::
286 To have the build system also tell the reason for the rebuild of each
287 target, use ``V=2``. The default is ``V=0``.
289 - Keep a backup kernel handy in case something goes wrong. This is
290 especially true for the development releases, since each new release
291 contains new code which has not been debugged. Make sure you keep a
292 backup of the modules corresponding to that kernel, as well. If you
293 are installing a new kernel with the same version number as your
294 working kernel, make a backup of your modules directory before you
295 do a ``make modules_install``.
297 Alternatively, before compiling, use the kernel config option
298 "LOCALVERSION" to append a unique suffix to the regular kernel version.
299 LOCALVERSION can be set in the "General Setup" menu.
301 - In order to boot your new kernel, you'll need to copy the kernel
302 image (e.g. .../linux/arch/x86/boot/bzImage after compilation)
303 to the place where your regular bootable kernel is found.
305 - Booting a kernel directly from a floppy without the assistance of a
306 bootloader such as LILO, is no longer supported.
308 If you boot Linux from the hard drive, chances are you use LILO, which
309 uses the kernel image as specified in the file /etc/lilo.conf. The
310 kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or
311 /boot/bzImage. To use the new kernel, save a copy of the old image
312 and copy the new image over the old one. Then, you MUST RERUN LILO
313 to update the loading map! If you don't, you won't be able to boot
314 the new kernel image.
316 Reinstalling LILO is usually a matter of running /sbin/lilo.
317 You may wish to edit /etc/lilo.conf to specify an entry for your
318 old kernel image (say, /vmlinux.old) in case the new one does not
319 work. See the LILO docs for more information.
321 After reinstalling LILO, you should be all set. Shutdown the system,
324 If you ever need to change the default root device, video mode,
325 etc. in the kernel image, use your bootloader's boot options
326 where appropriate. No need to recompile the kernel to change
329 - Reboot with the new kernel and enjoy.
331 If something goes wrong
332 -----------------------
334 - If you have problems that seem to be due to kernel bugs, please check
335 the file MAINTAINERS to see if there is a particular person associated
336 with the part of the kernel that you are having trouble with. If there
337 isn't anyone listed there, then the second best thing is to mail
338 them to me (torvalds@linux-foundation.org), and possibly to any other
339 relevant mailing-list or to the newsgroup.
341 - In all bug-reports, *please* tell what kernel you are talking about,
342 how to duplicate the problem, and what your setup is (use your common
343 sense). If the problem is new, tell me so, and if the problem is
344 old, please try to tell me when you first noticed it.
346 - If the bug results in a message like::
348 unable to handle kernel paging request at address C0000010
351 eax: xxxxxxxx ebx: xxxxxxxx ecx: xxxxxxxx edx: xxxxxxxx
352 esi: xxxxxxxx edi: xxxxxxxx ebp: xxxxxxxx
353 ds: xxxx es: xxxx fs: xxxx gs: xxxx
354 Pid: xx, process nr: xx
355 xx xx xx xx xx xx xx xx xx xx
357 or similar kernel debugging information on your screen or in your
358 system log, please duplicate it *exactly*. The dump may look
359 incomprehensible to you, but it does contain information that may
360 help debugging the problem. The text above the dump is also
361 important: it tells something about why the kernel dumped code (in
362 the above example, it's due to a bad kernel pointer). More information
363 on making sense of the dump is in Documentation/admin-guide/bug-hunting.rst
365 - If you compiled the kernel with CONFIG_KALLSYMS you can send the dump
366 as is, otherwise you will have to use the ``ksymoops`` program to make
367 sense of the dump (but compiling with CONFIG_KALLSYMS is usually preferred).
368 This utility can be downloaded from
369 https://www.kernel.org/pub/linux/utils/kernel/ksymoops/ .
370 Alternatively, you can do the dump lookup by hand:
372 - In debugging dumps like the above, it helps enormously if you can
373 look up what the EIP value means. The hex value as such doesn't help
374 me or anybody else very much: it will depend on your particular
375 kernel setup. What you should do is take the hex value from the EIP
376 line (ignore the ``0010:``), and look it up in the kernel namelist to
377 see which kernel function contains the offending address.
379 To find out the kernel function name, you'll need to find the system
380 binary associated with the kernel that exhibited the symptom. This is
381 the file 'linux/vmlinux'. To extract the namelist and match it against
382 the EIP from the kernel crash, do::
384 nm vmlinux | sort | less
386 This will give you a list of kernel addresses sorted in ascending
387 order, from which it is simple to find the function that contains the
388 offending address. Note that the address given by the kernel
389 debugging messages will not necessarily match exactly with the
390 function addresses (in fact, that is very unlikely), so you can't
391 just 'grep' the list: the list will, however, give you the starting
392 point of each kernel function, so by looking for the function that
393 has a starting address lower than the one you are searching for but
394 is followed by a function with a higher address you will find the one
395 you want. In fact, it may be a good idea to include a bit of
396 "context" in your problem report, giving a few lines around the
399 If you for some reason cannot do the above (you have a pre-compiled
400 kernel image or similar), telling me as much about your setup as
401 possible will help. Please read
402 'Documentation/admin-guide/reporting-issues.rst' for details.
404 - Alternatively, you can use gdb on a running kernel. (read-only; i.e. you
405 cannot change values or set break points.) To do this, first compile the
406 kernel with -g; edit arch/x86/Makefile appropriately, then do a ``make
407 clean``. You'll also need to enable CONFIG_PROC_FS (via ``make config``).
409 After you've rebooted with the new kernel, do ``gdb vmlinux /proc/kcore``.
410 You can now use all the usual gdb commands. The command to look up the
411 point where your system crashed is ``l *0xXXXXXXXX``. (Replace the XXXes
414 gdb'ing a non-running kernel currently fails because ``gdb`` (wrongly)
415 disregards the starting offset for which the kernel is compiled.
projects / mirror_ubuntu-jammy-kernel.git / blob