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 Unix clone written from scratch by Linus Torvalds with
  10  assistance from a loosely-knit team of hackers across the Net.
  11  It aims towards POSIX compliance. 
  13  It has all the features you would expect in a modern fully-fledged
  14  Unix, including true multitasking, virtual memory, shared libraries,
  15  demand loading, shared copy-on-write executables, proper memory
  16  management and TCP/IP networking. 
  18  It is distributed under the GNU General Public License - see the
  19  accompanying COPYING file for more details. 
  23  Linux was first developed for 386/486-based PCs.  These days it also
  24  runs on ARMs, DEC Alphas, SUN Sparcs, M68000 machines (like Atari and
  25  Amiga), MIPS and PowerPC, and others.
  29 - There is a lot of documentation available both in electronic form on
  30   the Internet and in books, both Linux-specific and pertaining to
  31   general UNIX questions.  I'd recommend looking into the documentation
  32   subdirectories on any Linux FTP site for the LDP (Linux Documentation
  33   Project) books.  This README is not meant to be documentation on the
  34   system: there are much better sources available.
  36 - There are various README files in the Documentation/ subdirectory:
  37   these typically contain kernel-specific installation notes for some 
  38   drivers for example. See ./Documentation/00-INDEX for a list of what
  39   is contained in each file.  Please read the Changes file, as it
  40   contains information about the problems, which may result by upgrading
  41   your kernel.
  43 - The Documentation/DocBook/ subdirectory contains several guides for
  44   kernel developers and users.  These guides can be rendered in a
  45   number of formats:  PostScript (.ps), PDF, and HTML, among others.
  46   After installation, "make psdocs", "make pdfdocs", or "make htmldocs"
  47   will render the documentation in the requested format.
  49INSTALLING the kernel:
  51 - If you install the full sources, put the kernel tarball in a
  52   directory where you have permissions (eg. your home directory) and
  53   unpack it:
  55                gzip -cd linux-2.6.XX.tar.gz | tar xvf -
  57   Replace "XX" with the version number of the latest kernel.
  59   Do NOT use the /usr/src/linux area! This area has a (usually
  60   incomplete) set of kernel headers that are used by the library header
  61   files.  They should match the library, and not get messed up by
  62   whatever the kernel-du-jour happens to be.
  64 - You can also upgrade between 2.6.xx releases by patching.  Patches are
  65   distributed in the traditional gzip and the new bzip2 format.  To
  66   install by patching, get all the newer patch files, enter the
  67   top level directory of the kernel source (linux-2.6.xx) and execute:
  69                gzip -cd ../patch-2.6.xx.gz | patch -p1
  71   or
  72                bzip2 -dc ../patch-2.6.xx.bz2 | patch -p1
  74   (repeat xx for all versions bigger than the version of your current
  75   source tree, _in_order_) and you should be ok.  You may want to remove
  76   the backup files (xxx~ or xxx.orig), and make sure that there are no
  77   failed patches (xxx# or xxx.rej). If there are, either you or me has
  78   made a mistake.
  80   Alternatively, the script patch-kernel can be used to automate this
  81   process.  It determines the current kernel version and applies any
  82   patches found.
  84                linux/scripts/patch-kernel linux
  86   The first argument in the command above is the location of the
  87   kernel source.  Patches are applied from the current directory, but
  88   an alternative directory can be specified as the second argument.
  90 - Make sure you have no stale .o files and dependencies lying around:
  92                cd linux
  93                make mrproper
  95   You should now have the sources correctly installed.
  99   Compiling and running the 2.6.xx kernels requires up-to-date
 100   versions of various software packages.  Consult
 101   ./Documentation/Changes for the minimum version numbers required
 102   and how to get updates for these packages.  Beware that using
 103   excessively old versions of these packages can cause indirect
 104   errors that are very difficult to track down, so don't assume that
 105   you can just update packages when obvious problems arise during
 106   build or operation.
 108BUILD directory for the kernel:
 110   When compiling the kernel all output files will per default be
 111   stored together with the kernel source code.
 112   Using the option "make O=output/dir" allow you to specify an alternate
 113   place for the output files (including .config).
 114   Example:
 115     kernel source code:        /usr/src/linux-2.6.N
 116     build directory:           /home/name/build/kernel
 118   To configure and build the kernel use:
 119   cd /usr/src/linux-2.6.N
 120   make O=/home/name/build/kernel menuconfig
 121   make O=/home/name/build/kernel
 122   sudo make O=/home/name/build/kernel modules_install install
 124   Please note: If the 'O=output/dir' option is used then it must be
 125   used for all invocations of make.
 127CONFIGURING the kernel:
 129   Do not skip this step even if you are only upgrading one minor
 130   version.  New configuration options are added in each release, and
 131   odd problems will turn up if the configuration files are not set up
 132   as expected.  If you want to carry your existing configuration to a
 133   new version with minimal work, use "make oldconfig", which will
 134   only ask you for the answers to new questions.
 136 - Alternate configuration commands are:
 137        "make menuconfig"  Text based color menus, radiolists & dialogs.
 138        "make xconfig"     X windows (Qt) based configuration tool.
 139        "make gconfig"     X windows (Gtk) based configuration tool.
 140        "make oldconfig"   Default all questions based on the contents of
 141                           your existing ./.config file.
 143        NOTES on "make config":
 144        - having unnecessary drivers will make the kernel bigger, and can
 145          under some circumstances lead to problems: probing for a
 146          nonexistent controller card may confuse your other controllers
 147        - compiling the kernel with "Processor type" set higher than 386
 148          will result in a kernel that does NOT work on a 386.  The
 149          kernel will detect this on bootup, and give up.
 150        - A kernel with math-emulation compiled in will still use the
 151          coprocessor if one is present: the math emulation will just
 152          never get used in that case.  The kernel will be slightly larger,
 153          but will work on different machines regardless of whether they
 154          have a math coprocessor or not. 
 155        - the "kernel hacking" configuration details usually result in a
 156          bigger or slower kernel (or both), and can even make the kernel
 157          less stable by configuring some routines to actively try to
 158          break bad code to find kernel problems (kmalloc()).  Thus you
 159          should probably answer 'n' to the questions for
 160          "development", "experimental", or "debugging" features.
 162 - Check the top Makefile for further site-dependent configuration
 163   (default SVGA mode etc). 
 165COMPILING the kernel:
 167 - Make sure you have gcc 2.95.3 available.
 168   gcc 2.91.66 (egcs-1.1.2), and gcc are known to miscompile
 169   some parts of the kernel, and are *no longer supported*.
 170   Also remember to upgrade your binutils package (for as/ld/nm and company)
 171   if necessary. For more information, refer to ./Documentation/Changes.
 173   Please note that you can still run a.out user programs with this kernel.
 175 - Do a "make bzImage" to create a compressed kernel image.  If you want
 176   to make a boot disk (without root filesystem or LILO), insert a floppy
 177   in your A: drive, and do a "make bzdisk".  It is also possible to do
 178   "make install" if you have lilo installed to suit the kernel makefiles,
 179   but you may want to check your particular lilo setup first. 
 181   To do the actual install you have to be root, but none of the normal
 182   build should require that. Don't take the name of root in vain.
 184 - In the unlikely event that your system cannot boot bzImage kernels you
 185   can still compile your kernel as zImage. However, since zImage support
 186   will be removed at some point in the future in favor of bzImage we
 187   encourage people having problems with booting bzImage kernels to report
 188   these, with detailed hardware configuration information, to the
 189   linux-kernel mailing list and to H. Peter Anvin <>.
 191 - If you configured any of the parts of the kernel as `modules', you
 192   will have to do "make modules" followed by "make modules_install".
 194 - Keep a backup kernel handy in case something goes wrong.  This is 
 195   especially true for the development releases, since each new release
 196   contains new code which has not been debugged.  Make sure you keep a
 197   backup of the modules corresponding to that kernel, as well.  If you
 198   are installing a new kernel with the same version number as your
 199   working kernel, make a backup of your modules directory before you
 200   do a "make modules_install".
 202 - In order to boot your new kernel, you'll need to copy the kernel
 203   image (found in .../linux/arch/i386/boot/bzImage after compilation)
 204   to the place where your regular bootable kernel is found. 
 206   For some, this is on a floppy disk, in which case you can copy the
 207   kernel bzImage file to /dev/fd0 to make a bootable floppy.
 209   If you boot Linux from the hard drive, chances are you use LILO which
 210   uses the kernel image as specified in the file /etc/lilo.conf.  The
 211   kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or
 212   /boot/bzImage.  To use the new kernel, save a copy of the old image
 213   and copy the new image over the old one.  Then, you MUST RERUN LILO
 214   to update the loading map!! If you don't, you won't be able to boot
 215   the new kernel image.
 217   Reinstalling LILO is usually a matter of running /sbin/lilo. 
 218   You may wish to edit /etc/lilo.conf to specify an entry for your
 219   old kernel image (say, /vmlinux.old) in case the new one does not
 220   work.  See the LILO docs for more information. 
 222   After reinstalling LILO, you should be all set.  Shutdown the system,
 223   reboot, and enjoy!
 225   If you ever need to change the default root device, video mode,
 226   ramdisk size, etc.  in the kernel image, use the 'rdev' program (or
 227   alternatively the LILO boot options when appropriate).  No need to
 228   recompile the kernel to change these parameters. 
 230 - Reboot with the new kernel and enjoy. 
 234 - If you have problems that seem to be due to kernel bugs, please check
 235   the file MAINTAINERS to see if there is a particular person associated
 236   with the part of the kernel that you are having trouble with. If there
 237   isn't anyone listed there, then the second best thing is to mail
 238   them to me (, and possibly to any other relevant
 239   mailing-list or to the newsgroup.
 241 - In all bug-reports, *please* tell what kernel you are talking about,
 242   how to duplicate the problem, and what your setup is (use your common
 243   sense).  If the problem is new, tell me so, and if the problem is
 244   old, please try to tell me when you first noticed it.
 246 - If the bug results in a message like
 248        unable to handle kernel paging request at address C0000010
 249        Oops: 0002
 250        EIP:   0010:XXXXXXXX
 251        eax: xxxxxxxx   ebx: xxxxxxxx   ecx: xxxxxxxx   edx: xxxxxxxx
 252        esi: xxxxxxxx   edi: xxxxxxxx   ebp: xxxxxxxx
 253        ds: xxxx  es: xxxx  fs: xxxx  gs: xxxx
 254        Pid: xx, process nr: xx
 255        xx xx xx xx xx xx xx xx xx xx
 257   or similar kernel debugging information on your screen or in your
 258   system log, please duplicate it *exactly*.  The dump may look
 259   incomprehensible to you, but it does contain information that may
 260   help debugging the problem.  The text above the dump is also
 261   important: it tells something about why the kernel dumped code (in
 262   the above example it's due to a bad kernel pointer). More information
 263   on making sense of the dump is in Documentation/oops-tracing.txt
 265 - You can use the "ksymoops" program to make sense of the dump.  This
 266   utility can be downloaded from
 267   ftp://ftp.<country>
 268   Alternately you can do the dump lookup by hand:
 270 - In debugging dumps like the above, it helps enormously if you can
 271   look up what the EIP value means.  The hex value as such doesn't help
 272   me or anybody else very much: it will depend on your particular
 273   kernel setup.  What you should do is take the hex value from the EIP
 274   line (ignore the "0010:"), and look it up in the kernel namelist to
 275   see which kernel function contains the offending address.
 277   To find out the kernel function name, you'll need to find the system
 278   binary associated with the kernel that exhibited the symptom.  This is
 279   the file 'linux/vmlinux'.  To extract the namelist and match it against
 280   the EIP from the kernel crash, do:
 282                nm vmlinux | sort | less
 284   This will give you a list of kernel addresses sorted in ascending
 285   order, from which it is simple to find the function that contains the
 286   offending address.  Note that the address given by the kernel
 287   debugging messages will not necessarily match exactly with the
 288   function addresses (in fact, that is very unlikely), so you can't
 289   just 'grep' the list: the list will, however, give you the starting
 290   point of each kernel function, so by looking for the function that
 291   has a starting address lower than the one you are searching for but
 292   is followed by a function with a higher address you will find the one
 293   you want.  In fact, it may be a good idea to include a bit of
 294   "context" in your problem report, giving a few lines around the
 295   interesting one. 
 297   If you for some reason cannot do the above (you have a pre-compiled
 298   kernel image or similar), telling me as much about your setup as
 299   possible will help. 
 301 - Alternately, you can use gdb on a running kernel. (read-only; i.e. you
 302   cannot change values or set break points.) To do this, first compile the
 303   kernel with -g; edit arch/i386/Makefile appropriately, then do a "make
 304   clean". You'll also need to enable CONFIG_PROC_FS (via "make config").
 306   After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore".
 307   You can now use all the usual gdb commands. The command to look up the
 308   point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes
 309   with the EIP value.)
 311   gdb'ing a non-running kernel currently fails because gdb (wrongly)
 312   disregards the starting offset for which the kernel is compiled.
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