README

   1         Linux kernel release 2.6.xx <http://kernel.org>
   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 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.
  12
  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.
  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   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,
  26   IBM S/390, MIPS, HP PA-RISC, Intel IA-64, DEC VAX, AMD x86-64, AXIS CRIS,
  27   and Renesas M32R architectures.
  28
  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
  35 DOCUMENTATION:
  36
  37  - There is a lot of documentation available both in electronic form on
  38    the Internet and in books, both Linux-specific and pertaining to
  39    general UNIX questions.  I'd recommend looking into the documentation
  40    subdirectories on any Linux FTP site for the LDP (Linux Documentation
  41    Project) books.  This README is not meant to be documentation on the
  42    system: there are much better sources available.
  43
  44  - There are various README files in the Documentation/ subdirectory:
  45    these typically contain kernel-specific installation notes for some
  46    drivers for example. See Documentation/00-INDEX for a list of what
  47    is contained in each file.  Please read the Changes file, as it
  48    contains information about the problems, which may result by upgrading
  49    your kernel.
  50
  51  - The Documentation/DocBook/ subdirectory contains several guides for
  52    kernel developers and users.  These guides can be rendered in a
  53    number of formats:  PostScript (.ps), PDF, and HTML, among others.
  54    After installation, "make psdocs", "make pdfdocs", or "make htmldocs"
  55    will render the documentation in the requested format.
  56
  57 INSTALLING the kernel:
  58
  59  - If you install the full sources, put the kernel tarball in a
  60    directory where you have permissions (eg. your home directory) and
  61    unpack it:
  62
  63                 gzip -cd linux-2.6.XX.tar.gz | tar xvf -
  64
  65    or
  66                 bzip2 -dc linux-2.6.XX.tar.bz2 | tar xvf -
  67
  68
  69    Replace "XX" with the version number of the latest kernel.
  70
  71    Do NOT use the /usr/src/linux area! This area has a (usually
  72    incomplete) set of kernel headers that are used by the library header
  73    files.  They should match the library, and not get messed up by
  74    whatever the kernel-du-jour happens to be.
  75
  76  - You can also upgrade between 2.6.xx releases by patching.  Patches are
  77    distributed in the traditional gzip and the newer bzip2 format.  To
  78    install by patching, get all the newer patch files, enter the
  79    top level directory of the kernel source (linux-2.6.xx) and execute:
  80
  81                 gzip -cd ../patch-2.6.xx.gz | patch -p1
  82
  83    or
  84                 bzip2 -dc ../patch-2.6.xx.bz2 | patch -p1
  85
  86    (repeat xx for all versions bigger than the version of your current
  87    source tree, _in_order_) and you should be ok.  You may want to remove
  88    the backup files (xxx~ or xxx.orig), and make sure that there are no
  89    failed patches (xxx# or xxx.rej). If there are, either you or me has
  90    made a mistake.
  91
  92    Unlike patches for the 2.6.x kernels, patches for the 2.6.x.y kernels
  93    (also known as the -stable kernels) are not incremental but instead apply
  94    directly to the base 2.6.x kernel.  Please read
  95    Documentation/applying-patches.txt for more information.
  96
  97    Alternatively, the script patch-kernel can be used to automate this
  98    process.  It determines the current kernel version and applies any
  99    patches found.
 100
 101                 linux/scripts/patch-kernel linux
 102
 103    The first argument in the command above is the location of the
 104    kernel source.  Patches are applied from the current directory, but
 105    an alternative directory can be specified as the second argument.
 106
 107  - If you are upgrading between releases using the stable series patches
 108    (for example, patch-2.6.xx.y), note that these "dot-releases" are
 109    not incremental and must be applied to the 2.6.xx base tree. For
 110    example, if your base kernel is 2.6.12 and you want to apply the
 111    2.6.12.3 patch, you do not and indeed must not first apply the
 112    2.6.12.1 and 2.6.12.2 patches. Similarly, if you are running kernel
 113    version 2.6.12.2 and want to jump to 2.6.12.3, you must first
 114    reverse the 2.6.12.2 patch (that is, patch -R) _before_ applying
 115    the 2.6.12.3 patch.
 116
 117  - Make sure you have no stale .o files and dependencies lying around:
 118
 119                 cd linux
 120                 make mrproper
 121
 122    You should now have the sources correctly installed.
 123
 124 SOFTWARE REQUIREMENTS
 125
 126    Compiling and running the 2.6.xx kernels requires up-to-date
 127    versions of various software packages.  Consult
 128    Documentation/Changes for the minimum version numbers required
 129    and how to get updates for these packages.  Beware that using
 130    excessively old versions of these packages can cause indirect
 131    errors that are very difficult to track down, so don't assume that
 132    you can just update packages when obvious problems arise during
 133    build or operation.
 134
 135 BUILD directory for the kernel:
 136
 137    When compiling the kernel all output files will per default be
 138    stored together with the kernel source code.
 139    Using the option "make O=output/dir" allow you to specify an alternate
 140    place for the output files (including .config).
 141    Example:
 142      kernel source code:        /usr/src/linux-2.6.N
 143      build directory:           /home/name/build/kernel
 144
 145    To configure and build the kernel use:
 146    cd /usr/src/linux-2.6.N
 147    make O=/home/name/build/kernel menuconfig
 148    make O=/home/name/build/kernel
 149    sudo make O=/home/name/build/kernel modules_install install
 150
 151    Please note: If the 'O=output/dir' option is used then it must be
 152    used for all invocations of make.
 153
 154 CONFIGURING the kernel:
 155
 156    Do not skip this step even if you are only upgrading one minor
 157    version.  New configuration options are added in each release, and
 158    odd problems will turn up if the configuration files are not set up
 159    as expected.  If you want to carry your existing configuration to a
 160    new version with minimal work, use "make oldconfig", which will
 161    only ask you for the answers to new questions.
 162
 163  - Alternate configuration commands are:
 164         "make menuconfig"  Text based color menus, radiolists & dialogs.
 165         "make xconfig"     X windows (Qt) based configuration tool.
 166         "make gconfig"     X windows (Gtk) based configuration tool.
 167         "make oldconfig"   Default all questions based on the contents of
 168                            your existing ./.config file.
 169         "make silentoldconfig"
 170                            Like above, but avoids cluttering the screen
 171                            with questions already answered.
 172
 173         NOTES on "make config":
 174         - having unnecessary drivers will make the kernel bigger, and can
 175           under some circumstances lead to problems: probing for a
 176           nonexistent controller card may confuse your other controllers
 177         - compiling the kernel with "Processor type" set higher than 386
 178           will result in a kernel that does NOT work on a 386.  The
 179           kernel will detect this on bootup, and give up.
 180         - A kernel with math-emulation compiled in will still use the
 181           coprocessor if one is present: the math emulation will just
 182           never get used in that case.  The kernel will be slightly larger,
 183           but will work on different machines regardless of whether they
 184           have a math coprocessor or not.
 185         - the "kernel hacking" configuration details usually result in a
 186           bigger or slower kernel (or both), and can even make the kernel
 187           less stable by configuring some routines to actively try to
 188           break bad code to find kernel problems (kmalloc()).  Thus you
 189           should probably answer 'n' to the questions for
 190           "development", "experimental", or "debugging" features.
 191
 192 COMPILING the kernel:
 193
 194  - Make sure you have at least gcc 3.2 available.
 195    For more information, refer to Documentation/Changes.
 196
 197    Please note that you can still run a.out user programs with this kernel.
 198
 199  - Do a "make" to create a compressed kernel image. It is also
 200    possible to do "make install" if you have lilo installed to suit the
 201    kernel makefiles, but you may want to check your particular lilo setup first.
 202
 203    To do the actual install you have to be root, but none of the normal
 204    build should require that. Don't take the name of root in vain.
 205
 206  - If you configured any of the parts of the kernel as `modules', you
 207    will also have to do "make modules_install".
 208
 209  - Keep a backup kernel handy in case something goes wrong.  This is
 210    especially true for the development releases, since each new release
 211    contains new code which has not been debugged.  Make sure you keep a
 212    backup of the modules corresponding to that kernel, as well.  If you
 213    are installing a new kernel with the same version number as your
 214    working kernel, make a backup of your modules directory before you
 215    do a "make modules_install".
 216    Alternatively, before compiling, use the kernel config option
 217    "LOCALVERSION" to append a unique suffix to the regular kernel version.
 218    LOCALVERSION can be set in the "General Setup" menu.
 219
 220  - In order to boot your new kernel, you'll need to copy the kernel
 221    image (e.g. .../linux/arch/i386/boot/bzImage after compilation)
 222    to the place where your regular bootable kernel is found.
 223
 224  - Booting a kernel directly from a floppy without the assistance of a
 225    bootloader such as LILO, is no longer supported.
 226
 227    If you boot Linux from the hard drive, chances are you use LILO which
 228    uses the kernel image as specified in the file /etc/lilo.conf.  The
 229    kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or
 230    /boot/bzImage.  To use the new kernel, save a copy of the old image
 231    and copy the new image over the old one.  Then, you MUST RERUN LILO
 232    to update the loading map!! If you don't, you won't be able to boot
 233    the new kernel image.
 234
 235    Reinstalling LILO is usually a matter of running /sbin/lilo.
 236    You may wish to edit /etc/lilo.conf to specify an entry for your
 237    old kernel image (say, /vmlinux.old) in case the new one does not
 238    work.  See the LILO docs for more information.
 239
 240    After reinstalling LILO, you should be all set.  Shutdown the system,
 241    reboot, and enjoy!
 242
 243    If you ever need to change the default root device, video mode,
 244    ramdisk size, etc.  in the kernel image, use the 'rdev' program (or
 245    alternatively the LILO boot options when appropriate).  No need to
 246    recompile the kernel to change these parameters.
 247
 248  - Reboot with the new kernel and enjoy.
 249
 250 IF SOMETHING GOES WRONG:
 251
 252  - If you have problems that seem to be due to kernel bugs, please check
 253    the file MAINTAINERS to see if there is a particular person associated
 254    with the part of the kernel that you are having trouble with. If there
 255    isn't anyone listed there, then the second best thing is to mail
 256    them to me (torvalds@osdl.org), and possibly to any other relevant
 257    mailing-list or to the newsgroup.
 258
 259  - In all bug-reports, *please* tell what kernel you are talking about,
 260    how to duplicate the problem, and what your setup is (use your common
 261    sense).  If the problem is new, tell me so, and if the problem is
 262    old, please try to tell me when you first noticed it.
 263
 264  - If the bug results in a message like
 265
 266         unable to handle kernel paging request at address C0000010
 267         Oops: 0002
 268         EIP:   0010:XXXXXXXX
 269         eax: xxxxxxxx   ebx: xxxxxxxx   ecx: xxxxxxxx   edx: xxxxxxxx
 270         esi: xxxxxxxx   edi: xxxxxxxx   ebp: xxxxxxxx
 271         ds: xxxx  es: xxxx  fs: xxxx  gs: xxxx
 272         Pid: xx, process nr: xx
 273         xx xx xx xx xx xx xx xx xx xx
 274
 275    or similar kernel debugging information on your screen or in your
 276    system log, please duplicate it *exactly*.  The dump may look
 277    incomprehensible to you, but it does contain information that may
 278    help debugging the problem.  The text above the dump is also
 279    important: it tells something about why the kernel dumped code (in
 280    the above example it's due to a bad kernel pointer). More information
 281    on making sense of the dump is in Documentation/oops-tracing.txt
 282
 283  - If you compiled the kernel with CONFIG_KALLSYMS you can send the dump
 284    as is, otherwise you will have to use the "ksymoops" program to make
 285    sense of the dump.  This utility can be downloaded from
 286    ftp://ftp.<country>.kernel.org/pub/linux/utils/kernel/ksymoops.
 287    Alternately you can do the dump lookup by hand:
 288
 289  - In debugging dumps like the above, it helps enormously if you can
 290    look up what the EIP value means.  The hex value as such doesn't help
 291    me or anybody else very much: it will depend on your particular
 292    kernel setup.  What you should do is take the hex value from the EIP
 293    line (ignore the "0010:"), and look it up in the kernel namelist to
 294    see which kernel function contains the offending address.
 295
 296    To find out the kernel function name, you'll need to find the system
 297    binary associated with the kernel that exhibited the symptom.  This is
 298    the file 'linux/vmlinux'.  To extract the namelist and match it against
 299    the EIP from the kernel crash, do:
 300
 301                 nm vmlinux | sort | less
 302
 303    This will give you a list of kernel addresses sorted in ascending
 304    order, from which it is simple to find the function that contains the
 305    offending address.  Note that the address given by the kernel
 306    debugging messages will not necessarily match exactly with the
 307    function addresses (in fact, that is very unlikely), so you can't
 308    just 'grep' the list: the list will, however, give you the starting
 309    point of each kernel function, so by looking for the function that
 310    has a starting address lower than the one you are searching for but
 311    is followed by a function with a higher address you will find the one
 312    you want.  In fact, it may be a good idea to include a bit of
 313    "context" in your problem report, giving a few lines around the
 314    interesting one.
 315
 316    If you for some reason cannot do the above (you have a pre-compiled
 317    kernel image or similar), telling me as much about your setup as
 318    possible will help.
 319
 320  - Alternately, you can use gdb on a running kernel. (read-only; i.e. you
 321    cannot change values or set break points.) To do this, first compile the
 322    kernel with -g; edit arch/i386/Makefile appropriately, then do a "make
 323    clean". You'll also need to enable CONFIG_PROC_FS (via "make config").
 324
 325    After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore".
 326    You can now use all the usual gdb commands. The command to look up the
 327    point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes
 328    with the EIP value.)
 329
 330    gdb'ing a non-running kernel currently fails because gdb (wrongly)
 331    disregards the starting offset for which the kernel is compiled.
 332