path: root/README
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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /README
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
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+ Linux kernel release 2.6.xx
+These are the release notes for Linux version 2.6. Read them carefully,
+as they tell you what this is all about, explain how to install the
+kernel, and what to do if something goes wrong.
+ Linux is a Unix clone written from scratch by Linus Torvalds with
+ assistance from a loosely-knit team of hackers across the Net.
+ It aims towards POSIX compliance.
+ It has all the features you would expect in a modern fully-fledged
+ Unix, including true multitasking, virtual memory, shared libraries,
+ demand loading, shared copy-on-write executables, proper memory
+ management and TCP/IP networking.
+ It is distributed under the GNU General Public License - see the
+ accompanying COPYING file for more details.
+ Linux was first developed for 386/486-based PCs. These days it also
+ runs on ARMs, DEC Alphas, SUN Sparcs, M68000 machines (like Atari and
+ Amiga), MIPS and PowerPC, and others.
+ - There is a lot of documentation available both in electronic form on
+ the Internet and in books, both Linux-specific and pertaining to
+ general UNIX questions. I'd recommend looking into the documentation
+ subdirectories on any Linux FTP site for the LDP (Linux Documentation
+ Project) books. This README is not meant to be documentation on the
+ system: there are much better sources available.
+ - There are various README files in the Documentation/ subdirectory:
+ these typically contain kernel-specific installation notes for some
+ drivers for example. See Documentation/00-INDEX for a list of what
+ is contained in each file. Please read the Changes file, as it
+ contains information about the problems, which may result by upgrading
+ your kernel.
+ - The Documentation/DocBook/ subdirectory contains several guides for
+ kernel developers and users. These guides can be rendered in a
+ number of formats: PostScript (.ps), PDF, and HTML, among others.
+ After installation, "make psdocs", "make pdfdocs", or "make htmldocs"
+ will render the documentation in the requested format.
+INSTALLING the kernel:
+ - If you install the full sources, put the kernel tarball in a
+ directory where you have permissions (eg. your home directory) and
+ unpack it:
+ gzip -cd linux-2.6.XX.tar.gz | tar xvf -
+ Replace "XX" with the version number of the latest kernel.
+ Do NOT use the /usr/src/linux area! This area has a (usually
+ incomplete) set of kernel headers that are used by the library header
+ files. They should match the library, and not get messed up by
+ whatever the kernel-du-jour happens to be.
+ - You can also upgrade between 2.6.xx releases by patching. Patches are
+ distributed in the traditional gzip and the new bzip2 format. To
+ install by patching, get all the newer patch files, enter the
+ top level directory of the kernel source (linux-2.6.xx) and execute:
+ gzip -cd ../patch-2.6.xx.gz | patch -p1
+ or
+ bzip2 -dc ../patch-2.6.xx.bz2 | patch -p1
+ (repeat xx for all versions bigger than the version of your current
+ source tree, _in_order_) and you should be ok. You may want to remove
+ the backup files (xxx~ or xxx.orig), and make sure that there are no
+ failed patches (xxx# or xxx.rej). If there are, either you or me has
+ made a mistake.
+ Alternatively, the script patch-kernel can be used to automate this
+ process. It determines the current kernel version and applies any
+ patches found.
+ linux/scripts/patch-kernel linux
+ The first argument in the command above is the location of the
+ kernel source. Patches are applied from the current directory, but
+ an alternative directory can be specified as the second argument.
+ - Make sure you have no stale .o files and dependencies lying around:
+ cd linux
+ make mrproper
+ You should now have the sources correctly installed.
+ Compiling and running the 2.6.xx kernels requires up-to-date
+ versions of various software packages. Consult
+ Documentation/Changes for the minimum version numbers required
+ and how to get updates for these packages. Beware that using
+ excessively old versions of these packages can cause indirect
+ errors that are very difficult to track down, so don't assume that
+ you can just update packages when obvious problems arise during
+ build or operation.
+BUILD directory for the kernel:
+ When compiling the kernel all output files will per default be
+ stored together with the kernel source code.
+ Using the option "make O=output/dir" allow you to specify an alternate
+ place for the output files (including .config).
+ Example:
+ kernel source code: /usr/src/linux-2.6.N
+ build directory: /home/name/build/kernel
+ To configure and build the kernel use:
+ cd /usr/src/linux-2.6.N
+ make O=/home/name/build/kernel menuconfig
+ make O=/home/name/build/kernel
+ sudo make O=/home/name/build/kernel modules_install install
+ Please note: If the 'O=output/dir' option is used then it must be
+ used for all invocations of make.
+CONFIGURING the kernel:
+ Do not skip this step even if you are only upgrading one minor
+ version. New configuration options are added in each release, and
+ odd problems will turn up if the configuration files are not set up
+ as expected. If you want to carry your existing configuration to a
+ new version with minimal work, use "make oldconfig", which will
+ only ask you for the answers to new questions.
+ - Alternate configuration commands are:
+ "make menuconfig" Text based color menus, radiolists & dialogs.
+ "make xconfig" X windows (Qt) based configuration tool.
+ "make gconfig" X windows (Gtk) based configuration tool.
+ "make oldconfig" Default all questions based on the contents of
+ your existing ./.config file.
+ NOTES on "make config":
+ - having unnecessary drivers will make the kernel bigger, and can
+ under some circumstances lead to problems: probing for a
+ nonexistent controller card may confuse your other controllers
+ - compiling the kernel with "Processor type" set higher than 386
+ will result in a kernel that does NOT work on a 386. The
+ kernel will detect this on bootup, and give up.
+ - A kernel with math-emulation compiled in will still use the
+ coprocessor if one is present: the math emulation will just
+ never get used in that case. The kernel will be slightly larger,
+ but will work on different machines regardless of whether they
+ have a math coprocessor or not.
+ - the "kernel hacking" configuration details usually result in a
+ bigger or slower kernel (or both), and can even make the kernel
+ less stable by configuring some routines to actively try to
+ break bad code to find kernel problems (kmalloc()). Thus you
+ should probably answer 'n' to the questions for
+ "development", "experimental", or "debugging" features.
+ - Check the top Makefile for further site-dependent configuration
+ (default SVGA mode etc).
+COMPILING the kernel:
+ - Make sure you have gcc 2.95.3 available.
+ gcc 2.91.66 (egcs-1.1.2), and gcc are known to miscompile
+ some parts of the kernel, and are *no longer supported*.
+ Also remember to upgrade your binutils package (for as/ld/nm and company)
+ if necessary. For more information, refer to Documentation/Changes.
+ Please note that you can still run a.out user programs with this kernel.
+ - Do a "make" to create a compressed kernel image. It is also
+ possible to do "make install" if you have lilo installed to suit the
+ kernel makefiles, but you may want to check your particular lilo setup first.
+ To do the actual install you have to be root, but none of the normal
+ build should require that. Don't take the name of root in vain.
+ - If you configured any of the parts of the kernel as `modules', you
+ will also have to do "make modules_install".
+ - Keep a backup kernel handy in case something goes wrong. This is
+ especially true for the development releases, since each new release
+ contains new code which has not been debugged. Make sure you keep a
+ backup of the modules corresponding to that kernel, as well. If you
+ are installing a new kernel with the same version number as your
+ working kernel, make a backup of your modules directory before you
+ do a "make modules_install".
+ - In order to boot your new kernel, you'll need to copy the kernel
+ image (e.g. .../linux/arch/i386/boot/bzImage after compilation)
+ to the place where your regular bootable kernel is found.
+ - Booting a kernel directly from a floppy without the assistance of a
+ bootloader such as LILO, is no longer supported.
+ If you boot Linux from the hard drive, chances are you use LILO which
+ uses the kernel image as specified in the file /etc/lilo.conf. The
+ kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or
+ /boot/bzImage. To use the new kernel, save a copy of the old image
+ and copy the new image over the old one. Then, you MUST RERUN LILO
+ to update the loading map!! If you don't, you won't be able to boot
+ the new kernel image.
+ Reinstalling LILO is usually a matter of running /sbin/lilo.
+ You may wish to edit /etc/lilo.conf to specify an entry for your
+ old kernel image (say, /vmlinux.old) in case the new one does not
+ work. See the LILO docs for more information.
+ After reinstalling LILO, you should be all set. Shutdown the system,
+ reboot, and enjoy!
+ If you ever need to change the default root device, video mode,
+ ramdisk size, etc. in the kernel image, use the 'rdev' program (or
+ alternatively the LILO boot options when appropriate). No need to
+ recompile the kernel to change these parameters.
+ - Reboot with the new kernel and enjoy.
+ - If you have problems that seem to be due to kernel bugs, please check
+ the file MAINTAINERS to see if there is a particular person associated
+ with the part of the kernel that you are having trouble with. If there
+ isn't anyone listed there, then the second best thing is to mail
+ them to me (torvalds@osdl.org), and possibly to any other relevant
+ mailing-list or to the newsgroup.
+ - In all bug-reports, *please* tell what kernel you are talking about,
+ how to duplicate the problem, and what your setup is (use your common
+ sense). If the problem is new, tell me so, and if the problem is
+ old, please try to tell me when you first noticed it.
+ - If the bug results in a message like
+ unable to handle kernel paging request at address C0000010
+ Oops: 0002
+ eax: xxxxxxxx ebx: xxxxxxxx ecx: xxxxxxxx edx: xxxxxxxx
+ esi: xxxxxxxx edi: xxxxxxxx ebp: xxxxxxxx
+ ds: xxxx es: xxxx fs: xxxx gs: xxxx
+ Pid: xx, process nr: xx
+ xx xx xx xx xx xx xx xx xx xx
+ or similar kernel debugging information on your screen or in your
+ system log, please duplicate it *exactly*. The dump may look
+ incomprehensible to you, but it does contain information that may
+ help debugging the problem. The text above the dump is also
+ important: it tells something about why the kernel dumped code (in
+ the above example it's due to a bad kernel pointer). More information
+ on making sense of the dump is in Documentation/oops-tracing.txt
+ - If you compiled the kernel with CONFIG_KALLSYMS you can send the dump
+ as is, otherwise you will have to use the "ksymoops" program to make
+ sense of the dump. This utility can be downloaded from
+ ftp://ftp.<country>.kernel.org/pub/linux/utils/kernel/ksymoops.
+ Alternately you can do the dump lookup by hand:
+ - In debugging dumps like the above, it helps enormously if you can
+ look up what the EIP value means. The hex value as such doesn't help
+ me or anybody else very much: it will depend on your particular
+ kernel setup. What you should do is take the hex value from the EIP
+ line (ignore the "0010:"), and look it up in the kernel namelist to
+ see which kernel function contains the offending address.
+ To find out the kernel function name, you'll need to find the system
+ binary associated with the kernel that exhibited the symptom. This is
+ the file 'linux/vmlinux'. To extract the namelist and match it against
+ the EIP from the kernel crash, do:
+ nm vmlinux | sort | less
+ This will give you a list of kernel addresses sorted in ascending
+ order, from which it is simple to find the function that contains the
+ offending address. Note that the address given by the kernel
+ debugging messages will not necessarily match exactly with the
+ function addresses (in fact, that is very unlikely), so you can't
+ just 'grep' the list: the list will, however, give you the starting
+ point of each kernel function, so by looking for the function that
+ has a starting address lower than the one you are searching for but
+ is followed by a function with a higher address you will find the one
+ you want. In fact, it may be a good idea to include a bit of
+ "context" in your problem report, giving a few lines around the
+ interesting one.
+ If you for some reason cannot do the above (you have a pre-compiled
+ kernel image or similar), telling me as much about your setup as
+ possible will help.
+ - Alternately, you can use gdb on a running kernel. (read-only; i.e. you
+ cannot change values or set break points.) To do this, first compile the
+ kernel with -g; edit arch/i386/Makefile appropriately, then do a "make
+ clean". You'll also need to enable CONFIG_PROC_FS (via "make config").
+ After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore".
+ You can now use all the usual gdb commands. The command to look up the
+ point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes
+ with the EIP value.)
+ gdb'ing a non-running kernel currently fails because gdb (wrongly)
+ disregards the starting offset for which the kernel is compiled.