Version:  2.0.40 2.2.26 2.4.37 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0 4.1 4.2


  1         Linux kernel release 4.x <>
  3 These are the release notes for Linux version 4.  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. 
  9   Linux is a clone of the operating system Unix, written from scratch by
 10   Linus Torvalds with assistance from a loosely-knit team of hackers across
 11   the Net. It aims towards POSIX and Single UNIX Specification compliance.
 13   It has all the features you would expect in a modern fully-fledged Unix,
 14   including true multitasking, virtual memory, shared libraries, demand
 15   loading, shared copy-on-write executables, proper memory management,
 16   and multistack networking including IPv4 and IPv6.
 18   It is distributed under the GNU General Public License - see the
 19   accompanying COPYING file for more details. 
 23   Although originally developed first for 32-bit x86-based PCs (386 or higher),
 24   today Linux also runs on (at least) the Compaq Alpha AXP, Sun SPARC and
 25   UltraSPARC, Motorola 68000, PowerPC, PowerPC64, ARM, Hitachi SuperH, Cell,
 26   IBM S/390, MIPS, HP PA-RISC, Intel IA-64, DEC VAX, AMD x86-64, AXIS CRIS,
 27   Xtensa, Tilera TILE, AVR32 and Renesas M32R architectures.
 29   Linux is easily portable to most general-purpose 32- or 64-bit architectures
 30   as long as they have a paged memory management unit (PMMU) and a port of the
 31   GNU C compiler (gcc) (part of The GNU Compiler Collection, GCC). Linux has
 32   also been ported to a number of architectures without a PMMU, although
 33   functionality is then obviously somewhat limited.
 34   Linux has also been ported to itself. You can now run the kernel as a
 35   userspace application - this is called UserMode Linux (UML).
 39  - There is a lot of documentation available both in electronic form on
 40    the Internet and in books, both Linux-specific and pertaining to
 41    general UNIX questions.  I'd recommend looking into the documentation
 42    subdirectories on any Linux FTP site for the LDP (Linux Documentation
 43    Project) books.  This README is not meant to be documentation on the
 44    system: there are much better sources available.
 46  - There are various README files in the Documentation/ subdirectory:
 47    these typically contain kernel-specific installation notes for some 
 48    drivers for example. See Documentation/00-INDEX for a list of what
 49    is contained in each file.  Please read the Changes file, as it
 50    contains information about the problems, which may result by upgrading
 51    your kernel.
 53  - The Documentation/DocBook/ subdirectory contains several guides for
 54    kernel developers and users.  These guides can be rendered in a
 55    number of formats:  PostScript (.ps), PDF, HTML, & man-pages, among others.
 56    After installation, "make psdocs", "make pdfdocs", "make htmldocs",
 57    or "make mandocs" will render the documentation in the requested format.
 59 INSTALLING the kernel source:
 61  - If you install the full sources, put the kernel tarball in a
 62    directory where you have permissions (eg. your home directory) and
 63    unpack it:
 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    Documentation/applying-patches.txt
 96    Alternatively, the script patch-kernel can be used to automate this
 97    process.  It determines the current kernel version and applies any
 98    patches found.
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:
108      cd linux
109      make mrproper
111    You should now have the sources correctly installed.
115    Compiling and running the 4.x kernels requires up-to-date
116    versions of various software packages.  Consult
117    Documentation/Changes for the minimum version numbers required
118    and how to get updates for these packages.  Beware that using
119    excessively old versions of these packages can cause indirect
120    errors that are very difficult to track down, so don't assume that
121    you can just update packages when obvious problems arise during
122    build or operation.
124 BUILD directory for the kernel:
126    When compiling the kernel, all output files will per default be
127    stored together with the kernel source code.
128    Using the option "make O=output/dir" allow you to specify an alternate
129    place for the output files (including .config).
130    Example:
132      kernel source code: /usr/src/linux-4.X
133      build directory:    /home/name/build/kernel
135    To configure and build the kernel, use:
137      cd /usr/src/linux-4.X
138      make O=/home/name/build/kernel menuconfig
139      make O=/home/name/build/kernel
140      sudo make O=/home/name/build/kernel modules_install install
142    Please note: If the 'O=output/dir' option is used, then it must be
143    used for all invocations of make.
145 CONFIGURING the kernel:
147    Do not skip this step even if you are only upgrading one minor
148    version.  New configuration options are added in each release, and
149    odd problems will turn up if the configuration files are not set up
150    as expected.  If you want to carry your existing configuration to a
151    new version with minimal work, use "make oldconfig", which will
152    only ask you for the answers to new questions.
154  - Alternative configuration commands are:
156      "make config"      Plain text interface.
158      "make menuconfig"  Text based color menus, radiolists & dialogs.
160      "make nconfig"     Enhanced text based color menus.
162      "make xconfig"     X windows (Qt) based configuration tool.
164      "make gconfig"     X windows (Gtk) based configuration tool.
166      "make oldconfig"   Default all questions based on the contents of
167                         your existing ./.config file and asking about
168                         new config symbols.
170      "make silentoldconfig"
171                         Like above, but avoids cluttering the screen
172                         with questions already answered.
173                         Additionally updates the dependencies.
175      "make olddefconfig"
176                         Like above, but sets new symbols to their default
177                         values without prompting.
179      "make defconfig"   Create a ./.config file by using the default
180                         symbol values from either arch/$ARCH/defconfig
181                         or arch/$ARCH/configs/${PLATFORM}_defconfig,
182                         depending on the architecture.
184      "make ${PLATFORM}_defconfig"
185                         Create a ./.config file by using the default
186                         symbol values from
187                         arch/$ARCH/configs/${PLATFORM}_defconfig.
188                         Use "make help" to get a list of all available
189                         platforms of your architecture.
191      "make allyesconfig"
192                         Create a ./.config file by setting symbol
193                         values to 'y' as much as possible.
195      "make allmodconfig"
196                         Create a ./.config file by setting symbol
197                         values to 'm' as much as possible.
199      "make allnoconfig" Create a ./.config file by setting symbol
200                         values to 'n' as much as possible.
202      "make randconfig"  Create a ./.config file by setting symbol
203                         values to random values.
205      "make localmodconfig" Create a config based on current config and
206                            loaded modules (lsmod). Disables any module
207                            option that is not needed for the loaded modules.
209                            To create a localmodconfig for another machine,
210                            store the lsmod of that machine into a file
211                            and pass it in as a LSMOD parameter.
213                    target$ lsmod > /tmp/mylsmod
214                    target$ scp /tmp/mylsmod host:/tmp
216                    host$ make LSMOD=/tmp/mylsmod localmodconfig
218                            The above also works when cross compiling.
220      "make localyesconfig" Similar to localmodconfig, except it will convert
221                            all module options to built in (=y) options.
223    You can find more information on using the Linux kernel config tools
224    in Documentation/kbuild/kconfig.txt.
226  - NOTES on "make config":
228     - Having unnecessary drivers will make the kernel bigger, and can
229       under some circumstances lead to problems: probing for a
230       nonexistent controller card may confuse your other controllers
232     - Compiling the kernel with "Processor type" set higher than 386
233       will result in a kernel that does NOT work on a 386.  The
234       kernel will detect this on bootup, and give up.
236     - A kernel with math-emulation compiled in will still use the
237       coprocessor if one is present: the math emulation will just
238       never get used in that case.  The kernel will be slightly larger,
239       but will work on different machines regardless of whether they
240       have a math coprocessor or not.
242     - The "kernel hacking" configuration details usually result in a
243       bigger or slower kernel (or both), and can even make the kernel
244       less stable by configuring some routines to actively try to
245       break bad code to find kernel problems (kmalloc()).  Thus you
246       should probably answer 'n' to the questions for "development",
247       "experimental", or "debugging" features.
249 COMPILING the kernel:
251  - Make sure you have at least gcc 3.2 available.
252    For more information, refer to Documentation/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 inserting
272    "V=1" in the "make" command.  E.g.:
274      make V=1 all
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/i386/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,
312    reboot, and enjoy!
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. 
323  - If you have problems that seem to be due to kernel bugs, please check
324    the file MAINTAINERS to see if there is a particular person associated
325    with the part of the kernel that you are having trouble with. If there
326    isn't anyone listed there, then the second best thing is to mail
327    them to me (, and possibly to any other
328    relevant mailing-list or to the newsgroup.
330  - In all bug-reports, *please* tell what kernel you are talking about,
331    how to duplicate the problem, and what your setup is (use your common
332    sense).  If the problem is new, tell me so, and if the problem is
333    old, please try to tell me when you first noticed it.
335  - If the bug results in a message like
337      unable to handle kernel paging request at address C0000010
338      Oops: 0002
339      EIP:   0010:XXXXXXXX
340      eax: xxxxxxxx   ebx: xxxxxxxx   ecx: xxxxxxxx   edx: xxxxxxxx
341      esi: xxxxxxxx   edi: xxxxxxxx   ebp: xxxxxxxx
342      ds: xxxx  es: xxxx  fs: xxxx  gs: xxxx
343      Pid: xx, process nr: xx
344      xx xx xx xx xx xx xx xx xx xx
346    or similar kernel debugging information on your screen or in your
347    system log, please duplicate it *exactly*.  The dump may look
348    incomprehensible to you, but it does contain information that may
349    help debugging the problem.  The text above the dump is also
350    important: it tells something about why the kernel dumped code (in
351    the above example, it's due to a bad kernel pointer). More information
352    on making sense of the dump is in Documentation/oops-tracing.txt
354  - If you compiled the kernel with CONFIG_KALLSYMS you can send the dump
355    as is, otherwise you will have to use the "ksymoops" program to make
356    sense of the dump (but compiling with CONFIG_KALLSYMS is usually preferred).
357    This utility can be downloaded from
358    ftp://ftp.<country> .
359    Alternatively, you can do the dump lookup by hand:
361  - In debugging dumps like the above, it helps enormously if you can
362    look up what the EIP value means.  The hex value as such doesn't help
363    me or anybody else very much: it will depend on your particular
364    kernel setup.  What you should do is take the hex value from the EIP
365    line (ignore the "0010:"), and look it up in the kernel namelist to
366    see which kernel function contains the offending address.
368    To find out the kernel function name, you'll need to find the system
369    binary associated with the kernel that exhibited the symptom.  This is
370    the file 'linux/vmlinux'.  To extract the namelist and match it against
371    the EIP from the kernel crash, do:
373      nm vmlinux | sort | less
375    This will give you a list of kernel addresses sorted in ascending
376    order, from which it is simple to find the function that contains the
377    offending address.  Note that the address given by the kernel
378    debugging messages will not necessarily match exactly with the
379    function addresses (in fact, that is very unlikely), so you can't
380    just 'grep' the list: the list will, however, give you the starting
381    point of each kernel function, so by looking for the function that
382    has a starting address lower than the one you are searching for but
383    is followed by a function with a higher address you will find the one
384    you want.  In fact, it may be a good idea to include a bit of
385    "context" in your problem report, giving a few lines around the
386    interesting one. 
388    If you for some reason cannot do the above (you have a pre-compiled
389    kernel image or similar), telling me as much about your setup as
390    possible will help.  Please read the REPORTING-BUGS document for details.
392  - Alternatively, you can use gdb on a running kernel. (read-only; i.e. you
393    cannot change values or set break points.) To do this, first compile the
394    kernel with -g; edit arch/i386/Makefile appropriately, then do a "make
395    clean". You'll also need to enable CONFIG_PROC_FS (via "make config").
397    After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore".
398    You can now use all the usual gdb commands. The command to look up the
399    point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes
400    with the EIP value.)
402    gdb'ing a non-running kernel currently fails because gdb (wrongly)
403    disregards the starting offset for which the kernel is compiled.

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