1        Linux kernel release 2.6.xx <>
   3These are the release notes for Linux version 2.6.  Read them carefully,
   4as they tell you what this is all about, explain how to install the
   5kernel, 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, 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.
  59INSTALLING 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                gzip -cd linux-2.6.XX.tar.gz | tar xvf -
  67   or
  68                bzip2 -dc linux-2.6.XX.tar.bz2 | tar xvf -
  71   Replace "XX" with the version number of the latest kernel.
  73   Do NOT use the /usr/src/linux area! This area has a (usually
  74   incomplete) set of kernel headers that are used by the library header
  75   files.  They should match the library, and not get messed up by
  76   whatever the kernel-du-jour happens to be.
  78 - You can also upgrade between 2.6.xx releases by patching.  Patches are
  79   distributed in the traditional gzip and the newer bzip2 format.  To
  80   install by patching, get all the newer patch files, enter the
  81   top level directory of the kernel source (linux-2.6.xx) and execute:
  83                gzip -cd ../patch-2.6.xx.gz | patch -p1
  85   or
  86                bzip2 -dc ../patch-2.6.xx.bz2 | patch -p1
  88   (repeat xx for all versions bigger than the version of your current
  89   source tree, _in_order_) and you should be ok.  You may want to remove
  90   the backup files (xxx~ or xxx.orig), and make sure that there are no
  91   failed patches (xxx# or xxx.rej). If there are, either you or me has
  92   made a mistake.
  94   Unlike patches for the 2.6.x kernels, patches for the 2.6.x.y kernels
  95   (also known as the -stable kernels) are not incremental but instead apply
  96   directly to the base 2.6.x kernel.  Please read
  97   Documentation/applying-patches.txt for more information.
  99   Alternatively, the script patch-kernel can be used to automate this
 100   process.  It determines the current kernel version and applies any
 101   patches found.
 103                linux/scripts/patch-kernel linux
 105   The first argument in the command above is the location of the
 106   kernel source.  Patches are applied from the current directory, but
 107   an alternative directory can be specified as the second argument.
 109 - If you are upgrading between releases using the stable series patches
 110   (for example, patch-2.6.xx.y), note that these "dot-releases" are
 111   not incremental and must be applied to the 2.6.xx base tree. For
 112   example, if your base kernel is 2.6.12 and you want to apply the
 113 patch, you do not and indeed must not first apply the
 114 and patches. Similarly, if you are running kernel
 115   version and want to jump to, you must first
 116   reverse the patch (that is, patch -R) _before_ applying
 117   the patch.
 118   You can read more on this in Documentation/applying-patches.txt
 120 - Make sure you have no stale .o files and dependencies lying around:
 122                cd linux
 123                make mrproper
 125   You should now have the sources correctly installed.
 129   Compiling and running the 2.6.xx kernels requires up-to-date
 130   versions of various software packages.  Consult
 131   Documentation/Changes for the minimum version numbers required
 132   and how to get updates for these packages.  Beware that using
 133   excessively old versions of these packages can cause indirect
 134   errors that are very difficult to track down, so don't assume that
 135   you can just update packages when obvious problems arise during
 136   build or operation.
 138BUILD directory for the kernel:
 140   When compiling the kernel all output files will per default be
 141   stored together with the kernel source code.
 142   Using the option "make O=output/dir" allow you to specify an alternate
 143   place for the output files (including .config).
 144   Example:
 145     kernel source code:        /usr/src/linux-2.6.N
 146     build directory:           /home/name/build/kernel
 148   To configure and build the kernel use:
 149   cd /usr/src/linux-2.6.N
 150   make O=/home/name/build/kernel menuconfig
 151   make O=/home/name/build/kernel
 152   sudo make O=/home/name/build/kernel modules_install install
 154   Please note: If the 'O=output/dir' option is used then it must be
 155   used for all invocations of make.
 157CONFIGURING the kernel:
 159   Do not skip this step even if you are only upgrading one minor
 160   version.  New configuration options are added in each release, and
 161   odd problems will turn up if the configuration files are not set up
 162   as expected.  If you want to carry your existing configuration to a
 163   new version with minimal work, use "make oldconfig", which will
 164   only ask you for the answers to new questions.
 166 - Alternate configuration commands are:
 167        "make config"      Plain text interface.
 168        "make menuconfig"  Text based color menus, radiolists & dialogs.
 169        "make xconfig"     X windows (Qt) based configuration tool.
 170        "make gconfig"     X windows (Gtk) based configuration tool.
 171        "make oldconfig"   Default all questions based on the contents of
 172                           your existing ./.config file and asking about
 173                           new config symbols.
 174        "make silentoldconfig"
 175                           Like above, but avoids cluttering the screen
 176                           with questions already answered.
 177                           Additionally updates the dependencies.
 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.
 182        "make ${PLATFORM}_defconfig"
 183                          Create a ./.config file by using the default
 184                          symbol values from
 185                          arch/$ARCH/configs/${PLATFORM}_defconfig.
 186                          Use "make help" to get a list of all available
 187                          platforms of your architecture.
 188        "make allyesconfig"
 189                           Create a ./.config file by setting symbol
 190                           values to 'y' as much as possible.
 191        "make allmodconfig"
 192                           Create a ./.config file by setting symbol
 193                           values to 'm' as much as possible.
 194        "make allnoconfig" Create a ./.config file by setting symbol
 195                           values to 'n' as much as possible.
 196        "make randconfig"  Create a ./.config file by setting symbol
 197                           values to random values.
 199   You can find more information on using the Linux kernel config tools
 200   in Documentation/kbuild/kconfig.txt.
 202        NOTES on "make config":
 203        - having unnecessary drivers will make the kernel bigger, and can
 204          under some circumstances lead to problems: probing for a
 205          nonexistent controller card may confuse your other controllers
 206        - compiling the kernel with "Processor type" set higher than 386
 207          will result in a kernel that does NOT work on a 386.  The
 208          kernel will detect this on bootup, and give up.
 209        - A kernel with math-emulation compiled in will still use the
 210          coprocessor if one is present: the math emulation will just
 211          never get used in that case.  The kernel will be slightly larger,
 212          but will work on different machines regardless of whether they
 213          have a math coprocessor or not. 
 214        - the "kernel hacking" configuration details usually result in a
 215          bigger or slower kernel (or both), and can even make the kernel
 216          less stable by configuring some routines to actively try to
 217          break bad code to find kernel problems (kmalloc()).  Thus you
 218          should probably answer 'n' to the questions for
 219          "development", "experimental", or "debugging" features.
 221COMPILING the kernel:
 223 - Make sure you have at least gcc 3.2 available.
 224   For more information, refer to Documentation/Changes.
 226   Please note that you can still run a.out user programs with this kernel.
 228 - Do a "make" to create a compressed kernel image. It is also
 229   possible to do "make install" if you have lilo installed to suit the
 230   kernel makefiles, but you may want to check your particular lilo setup first.
 232   To do the actual install you have to be root, but none of the normal
 233   build should require that. Don't take the name of root in vain.
 235 - If you configured any of the parts of the kernel as `modules', you
 236   will also have to do "make modules_install".
 238 - Verbose kernel compile/build output:
 240   Normally the kernel build system runs in a fairly quiet mode (but not
 241   totally silent).  However, sometimes you or other kernel developers need
 242   to see compile, link, or other commands exactly as they are executed.
 243   For this, use "verbose" build mode.  This is done by inserting
 244   "V=1" in the "make" command.  E.g.:
 246        make V=1 all
 248   To have the build system also tell the reason for the rebuild of each
 249   target, use "V=2".  The default is "V=0".
 251 - Keep a backup kernel handy in case something goes wrong.  This is 
 252   especially true for the development releases, since each new release
 253   contains new code which has not been debugged.  Make sure you keep a
 254   backup of the modules corresponding to that kernel, as well.  If you
 255   are installing a new kernel with the same version number as your
 256   working kernel, make a backup of your modules directory before you
 257   do a "make modules_install".
 258   Alternatively, before compiling, use the kernel config option
 259   "LOCALVERSION" to append a unique suffix to the regular kernel version.
 260   LOCALVERSION can be set in the "General Setup" menu.
 262 - In order to boot your new kernel, you'll need to copy the kernel
 263   image (e.g. .../linux/arch/i386/boot/bzImage after compilation)
 264   to the place where your regular bootable kernel is found. 
 266 - Booting a kernel directly from a floppy without the assistance of a
 267   bootloader such as LILO, is no longer supported.
 269   If you boot Linux from the hard drive, chances are you use LILO which
 270   uses the kernel image as specified in the file /etc/lilo.conf.  The
 271   kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or
 272   /boot/bzImage.  To use the new kernel, save a copy of the old image
 273   and copy the new image over the old one.  Then, you MUST RERUN LILO
 274   to update the loading map!! If you don't, you won't be able to boot
 275   the new kernel image.
 277   Reinstalling LILO is usually a matter of running /sbin/lilo. 
 278   You may wish to edit /etc/lilo.conf to specify an entry for your
 279   old kernel image (say, /vmlinux.old) in case the new one does not
 280   work.  See the LILO docs for more information. 
 282   After reinstalling LILO, you should be all set.  Shutdown the system,
 283   reboot, and enjoy!
 285   If you ever need to change the default root device, video mode,
 286   ramdisk size, etc.  in the kernel image, use the 'rdev' program (or
 287   alternatively the LILO boot options when appropriate).  No need to
 288   recompile the kernel to change these parameters. 
 290 - Reboot with the new kernel and enjoy. 
 294 - If you have problems that seem to be due to kernel bugs, please check
 295   the file MAINTAINERS to see if there is a particular person associated
 296   with the part of the kernel that you are having trouble with. If there
 297   isn't anyone listed there, then the second best thing is to mail
 298   them to me (, and possibly to any other
 299   relevant mailing-list or to the newsgroup.
 301 - In all bug-reports, *please* tell what kernel you are talking about,
 302   how to duplicate the problem, and what your setup is (use your common
 303   sense).  If the problem is new, tell me so, and if the problem is
 304   old, please try to tell me when you first noticed it.
 306 - If the bug results in a message like
 308        unable to handle kernel paging request at address C0000010
 309        Oops: 0002
 310        EIP:   0010:XXXXXXXX
 311        eax: xxxxxxxx   ebx: xxxxxxxx   ecx: xxxxxxxx   edx: xxxxxxxx
 312        esi: xxxxxxxx   edi: xxxxxxxx   ebp: xxxxxxxx
 313        ds: xxxx  es: xxxx  fs: xxxx  gs: xxxx
 314        Pid: xx, process nr: xx
 315        xx xx xx xx xx xx xx xx xx xx
 317   or similar kernel debugging information on your screen or in your
 318   system log, please duplicate it *exactly*.  The dump may look
 319   incomprehensible to you, but it does contain information that may
 320   help debugging the problem.  The text above the dump is also
 321   important: it tells something about why the kernel dumped code (in
 322   the above example it's due to a bad kernel pointer). More information
 323   on making sense of the dump is in Documentation/oops-tracing.txt
 325 - If you compiled the kernel with CONFIG_KALLSYMS you can send the dump
 326   as is, otherwise you will have to use the "ksymoops" program to make
 327   sense of the dump (but compiling with CONFIG_KALLSYMS is usually preferred).
 328   This utility can be downloaded from
 329   ftp://ftp.<country> .
 330   Alternately you can do the dump lookup by hand:
 332 - In debugging dumps like the above, it helps enormously if you can
 333   look up what the EIP value means.  The hex value as such doesn't help
 334   me or anybody else very much: it will depend on your particular
 335   kernel setup.  What you should do is take the hex value from the EIP
 336   line (ignore the "0010:"), and look it up in the kernel namelist to
 337   see which kernel function contains the offending address.
 339   To find out the kernel function name, you'll need to find the system
 340   binary associated with the kernel that exhibited the symptom.  This is
 341   the file 'linux/vmlinux'.  To extract the namelist and match it against
 342   the EIP from the kernel crash, do:
 344                nm vmlinux | sort | less
 346   This will give you a list of kernel addresses sorted in ascending
 347   order, from which it is simple to find the function that contains the
 348   offending address.  Note that the address given by the kernel
 349   debugging messages will not necessarily match exactly with the
 350   function addresses (in fact, that is very unlikely), so you can't
 351   just 'grep' the list: the list will, however, give you the starting
 352   point of each kernel function, so by looking for the function that
 353   has a starting address lower than the one you are searching for but
 354   is followed by a function with a higher address you will find the one
 355   you want.  In fact, it may be a good idea to include a bit of
 356   "context" in your problem report, giving a few lines around the
 357   interesting one. 
 359   If you for some reason cannot do the above (you have a pre-compiled
 360   kernel image or similar), telling me as much about your setup as
 361   possible will help.  Please read the REPORTING-BUGS document for details.
 363 - Alternately, you can use gdb on a running kernel. (read-only; i.e. you
 364   cannot change values or set break points.) To do this, first compile the
 365   kernel with -g; edit arch/i386/Makefile appropriately, then do a "make
 366   clean". You'll also need to enable CONFIG_PROC_FS (via "make config").
 368   After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore".
 369   You can now use all the usual gdb commands. The command to look up the
 370   point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes
 371   with the EIP value.)
 373   gdb'ing a non-running kernel currently fails because gdb (wrongly)
 374   disregards the starting offset for which the kernel is compiled.