README

   1         Linux kernel release 2.6.xx
   2
   3 These are the release notes for Linux version 2.6.  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.
   6
   7 WHAT IS LINUX?
   8
   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.
  12
  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.
  17
  18   It is distributed under the GNU General Public License - see the
  19   accompanying COPYING file for more details.
  20
  21 ON WHAT HARDWARE DOES IT RUN?
  22
  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.
  26
  27 DOCUMENTATION:
  28
  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.
  35
  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.
  42
  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.
  48
  49 INSTALLING the kernel:
  50
  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:
  54
  55                 gzip -cd linux-2.6.XX.tar.gz | tar xvf -
  56
  57    Replace "XX" with the version number of the latest kernel.
  58
  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.
  63
  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:
  68
  69                 gzip -cd ../patch-2.6.xx.gz | patch -p1
  70
  71    or
  72                 bzip2 -dc ../patch-2.6.xx.bz2 | patch -p1
  73
  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.
  79
  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.
  83
  84                 linux/scripts/patch-kernel linux
  85
  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.
  89
  90  - If you are upgrading between releases using the stable series patches
  91    (for example, patch-2.6.xx.y), note that these "dot-releases" are
  92    not incremental and must be applied to the 2.6.xx base tree. For
  93    example, if your base kernel is 2.6.12 and you want to apply the
  94    2.6.12.3 patch, you do not and indeed must not first apply the
  95    2.6.12.1 and 2.6.12.2 patches. Similarly, if you are running kernel
  96    version 2.6.12.2 and want to jump to 2.6.12.3, you must first
  97    reverse the 2.6.12.2 patch (that is, patch -R) _before_ applying
  98    the 2.6.12.3 patch.
  99
 100  - Make sure you have no stale .o files and dependencies lying around:
 101
 102                 cd linux
 103                 make mrproper
 104
 105    You should now have the sources correctly installed.
 106
 107 SOFTWARE REQUIREMENTS
 108
 109    Compiling and running the 2.6.xx kernels requires up-to-date
 110    versions of various software packages.  Consult
 111    Documentation/Changes for the minimum version numbers required
 112    and how to get updates for these packages.  Beware that using
 113    excessively old versions of these packages can cause indirect
 114    errors that are very difficult to track down, so don't assume that
 115    you can just update packages when obvious problems arise during
 116    build or operation.
 117
 118 BUILD directory for the kernel:
 119
 120    When compiling the kernel all output files will per default be
 121    stored together with the kernel source code.
 122    Using the option "make O=output/dir" allow you to specify an alternate
 123    place for the output files (including .config).
 124    Example:
 125      kernel source code:        /usr/src/linux-2.6.N
 126      build directory:           /home/name/build/kernel
 127
 128    To configure and build the kernel use:
 129    cd /usr/src/linux-2.6.N
 130    make O=/home/name/build/kernel menuconfig
 131    make O=/home/name/build/kernel
 132    sudo make O=/home/name/build/kernel modules_install install
 133
 134    Please note: If the 'O=output/dir' option is used then it must be
 135    used for all invocations of make.
 136
 137 CONFIGURING the kernel:
 138
 139    Do not skip this step even if you are only upgrading one minor
 140    version.  New configuration options are added in each release, and
 141    odd problems will turn up if the configuration files are not set up
 142    as expected.  If you want to carry your existing configuration to a
 143    new version with minimal work, use "make oldconfig", which will
 144    only ask you for the answers to new questions.
 145
 146  - Alternate configuration commands are:
 147         "make menuconfig"  Text based color menus, radiolists & dialogs.
 148         "make xconfig"     X windows (Qt) based configuration tool.
 149         "make gconfig"     X windows (Gtk) based configuration tool.
 150         "make oldconfig"   Default all questions based on the contents of
 151                            your existing ./.config file.
 152
 153         NOTES on "make config":
 154         - having unnecessary drivers will make the kernel bigger, and can
 155           under some circumstances lead to problems: probing for a
 156           nonexistent controller card may confuse your other controllers
 157         - compiling the kernel with "Processor type" set higher than 386
 158           will result in a kernel that does NOT work on a 386.  The
 159           kernel will detect this on bootup, and give up.
 160         - A kernel with math-emulation compiled in will still use the
 161           coprocessor if one is present: the math emulation will just
 162           never get used in that case.  The kernel will be slightly larger,
 163           but will work on different machines regardless of whether they
 164           have a math coprocessor or not.
 165         - the "kernel hacking" configuration details usually result in a
 166           bigger or slower kernel (or both), and can even make the kernel
 167           less stable by configuring some routines to actively try to
 168           break bad code to find kernel problems (kmalloc()).  Thus you
 169           should probably answer 'n' to the questions for
 170           "development", "experimental", or "debugging" features.
 171
 172  - Check the top Makefile for further site-dependent configuration
 173    (default SVGA mode etc).
 174
 175 COMPILING the kernel:
 176
 177  - Make sure you have gcc 2.95.3 available.
 178    gcc 2.91.66 (egcs-1.1.2), and gcc 2.7.2.3 are known to miscompile
 179    some parts of the kernel, and are *no longer supported*.
 180    Also remember to upgrade your binutils package (for as/ld/nm and company)
 181    if necessary. For more information, refer to Documentation/Changes.
 182
 183    Please note that you can still run a.out user programs with this kernel.
 184
 185  - Do a "make" to create a compressed kernel image. It is also
 186    possible to do "make install" if you have lilo installed to suit the
 187    kernel makefiles, but you may want to check your particular lilo setup first.
 188
 189    To do the actual install you have to be root, but none of the normal
 190    build should require that. Don't take the name of root in vain.
 191
 192  - If you configured any of the parts of the kernel as `modules', you
 193    will also have to do "make modules_install".
 194
 195  - Keep a backup kernel handy in case something goes wrong.  This is
 196    especially true for the development releases, since each new release
 197    contains new code which has not been debugged.  Make sure you keep a
 198    backup of the modules corresponding to that kernel, as well.  If you
 199    are installing a new kernel with the same version number as your
 200    working kernel, make a backup of your modules directory before you
 201    do a "make modules_install".
 202
 203  - In order to boot your new kernel, you'll need to copy the kernel
 204    image (e.g. .../linux/arch/i386/boot/bzImage after compilation)
 205    to the place where your regular bootable kernel is found.
 206
 207  - Booting a kernel directly from a floppy without the assistance of a
 208    bootloader such as LILO, is no longer supported.
 209
 210    If you boot Linux from the hard drive, chances are you use LILO which
 211    uses the kernel image as specified in the file /etc/lilo.conf.  The
 212    kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or
 213    /boot/bzImage.  To use the new kernel, save a copy of the old image
 214    and copy the new image over the old one.  Then, you MUST RERUN LILO
 215    to update the loading map!! If you don't, you won't be able to boot
 216    the new kernel image.
 217
 218    Reinstalling LILO is usually a matter of running /sbin/lilo.
 219    You may wish to edit /etc/lilo.conf to specify an entry for your
 220    old kernel image (say, /vmlinux.old) in case the new one does not
 221    work.  See the LILO docs for more information.
 222
 223    After reinstalling LILO, you should be all set.  Shutdown the system,
 224    reboot, and enjoy!
 225
 226    If you ever need to change the default root device, video mode,
 227    ramdisk size, etc.  in the kernel image, use the 'rdev' program (or
 228    alternatively the LILO boot options when appropriate).  No need to
 229    recompile the kernel to change these parameters.
 230
 231  - Reboot with the new kernel and enjoy.
 232
 233 IF SOMETHING GOES WRONG:
 234
 235  - If you have problems that seem to be due to kernel bugs, please check
 236    the file MAINTAINERS to see if there is a particular person associated
 237    with the part of the kernel that you are having trouble with. If there
 238    isn't anyone listed there, then the second best thing is to mail
 239    them to me (torvalds@osdl.org), and possibly to any other relevant
 240    mailing-list or to the newsgroup.
 241
 242  - In all bug-reports, *please* tell what kernel you are talking about,
 243    how to duplicate the problem, and what your setup is (use your common
 244    sense).  If the problem is new, tell me so, and if the problem is
 245    old, please try to tell me when you first noticed it.
 246
 247  - If the bug results in a message like
 248
 249         unable to handle kernel paging request at address C0000010
 250         Oops: 0002
 251         EIP:   0010:XXXXXXXX
 252         eax: xxxxxxxx   ebx: xxxxxxxx   ecx: xxxxxxxx   edx: xxxxxxxx
 253         esi: xxxxxxxx   edi: xxxxxxxx   ebp: xxxxxxxx
 254         ds: xxxx  es: xxxx  fs: xxxx  gs: xxxx
 255         Pid: xx, process nr: xx
 256         xx xx xx xx xx xx xx xx xx xx
 257
 258    or similar kernel debugging information on your screen or in your
 259    system log, please duplicate it *exactly*.  The dump may look
 260    incomprehensible to you, but it does contain information that may
 261    help debugging the problem.  The text above the dump is also
 262    important: it tells something about why the kernel dumped code (in
 263    the above example it's due to a bad kernel pointer). More information
 264    on making sense of the dump is in Documentation/oops-tracing.txt
 265
 266  - If you compiled the kernel with CONFIG_KALLSYMS you can send the dump
 267    as is, otherwise you will have to use the "ksymoops" program to make
 268    sense of the dump.  This utility can be downloaded from
 269    ftp://ftp.<country>.kernel.org/pub/linux/utils/kernel/ksymoops.
 270    Alternately you can do the dump lookup by hand:
 271
 272  - In debugging dumps like the above, it helps enormously if you can
 273    look up what the EIP value means.  The hex value as such doesn't help
 274    me or anybody else very much: it will depend on your particular
 275    kernel setup.  What you should do is take the hex value from the EIP
 276    line (ignore the "0010:"), and look it up in the kernel namelist to
 277    see which kernel function contains the offending address.
 278
 279    To find out the kernel function name, you'll need to find the system
 280    binary associated with the kernel that exhibited the symptom.  This is
 281    the file 'linux/vmlinux'.  To extract the namelist and match it against
 282    the EIP from the kernel crash, do:
 283
 284                 nm vmlinux | sort | less
 285
 286    This will give you a list of kernel addresses sorted in ascending
 287    order, from which it is simple to find the function that contains the
 288    offending address.  Note that the address given by the kernel
 289    debugging messages will not necessarily match exactly with the
 290    function addresses (in fact, that is very unlikely), so you can't
 291    just 'grep' the list: the list will, however, give you the starting
 292    point of each kernel function, so by looking for the function that
 293    has a starting address lower than the one you are searching for but
 294    is followed by a function with a higher address you will find the one
 295    you want.  In fact, it may be a good idea to include a bit of
 296    "context" in your problem report, giving a few lines around the
 297    interesting one.
 298
 299    If you for some reason cannot do the above (you have a pre-compiled
 300    kernel image or similar), telling me as much about your setup as
 301    possible will help.
 302
 303  - Alternately, you can use gdb on a running kernel. (read-only; i.e. you
 304    cannot change values or set break points.) To do this, first compile the
 305    kernel with -g; edit arch/i386/Makefile appropriately, then do a "make
 306    clean". You'll also need to enable CONFIG_PROC_FS (via "make config").
 307
 308    After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore".
 309    You can now use all the usual gdb commands. The command to look up the
 310    point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes
 311    with the EIP value.)
 312
 313    gdb'ing a non-running kernel currently fails because gdb (wrongly)
 314    disregards the starting offset for which the kernel is compiled.
 315