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, 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.
  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   Linux has also been ported to itself. You can now run the kernel as a
  35   userspace application - this is called UserMode Linux (UML).
  36
  37 DOCUMENTATION:
  38
  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.
  45
  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.
  52
  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.
  58
  59 INSTALLING the kernel source:
  60
  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:
  64
  65                 gzip -cd linux-2.6.XX.tar.gz | tar xvf -
  66
  67    or
  68                 bzip2 -dc linux-2.6.XX.tar.bz2 | tar xvf -
  69
  70
  71    Replace "XX" with the version number of the latest kernel.
  72
  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.
  77
  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:
  82
  83                 gzip -cd ../patch-2.6.xx.gz | patch -p1
  84
  85    or
  86                 bzip2 -dc ../patch-2.6.xx.bz2 | patch -p1
  87
  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.
  93
  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.
  98
  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.
 102
 103                 linux/scripts/patch-kernel linux
 104
 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.
 108
 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    2.6.12.3 patch, you do not and indeed must not first apply the
 114    2.6.12.1 and 2.6.12.2 patches. Similarly, if you are running kernel
 115    version 2.6.12.2 and want to jump to 2.6.12.3, you must first
 116    reverse the 2.6.12.2 patch (that is, patch -R) _before_ applying
 117    the 2.6.12.3 patch.
 118    You can read more on this in Documentation/applying-patches.txt
 119
 120  - Make sure you have no stale .o files and dependencies lying around:
 121
 122                 cd linux
 123                 make mrproper
 124
 125    You should now have the sources correctly installed.
 126
 127 SOFTWARE REQUIREMENTS
 128
 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.
 137
 138 BUILD directory for the kernel:
 139
 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
 147
 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
 153
 154    Please note: If the 'O=output/dir' option is used then it must be
 155    used for all invocations of make.
 156
 157 CONFIGURING the kernel:
 158
 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.
 165
 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         "make defconfig"   Create a ./.config file by using the default
 178                            symbol values from arch/$ARCH/defconfig.
 179         "make allyesconfig"
 180                            Create a ./.config file by setting symbol
 181                            values to 'y' as much as possible.
 182         "make allmodconfig"
 183                            Create a ./.config file by setting symbol
 184                            values to 'm' as much as possible.
 185         "make allnoconfig" Create a ./.config file by setting symbol
 186                            values to 'n' as much as possible.
 187         "make randconfig"  Create a ./.config file by setting symbol
 188                            values to random values.
 189
 190    You can find more information on using the Linux kernel config tools
 191    in Documentation/kbuild/kconfig.txt.
 192
 193         NOTES on "make config":
 194         - having unnecessary drivers will make the kernel bigger, and can
 195           under some circumstances lead to problems: probing for a
 196           nonexistent controller card may confuse your other controllers
 197         - compiling the kernel with "Processor type" set higher than 386
 198           will result in a kernel that does NOT work on a 386.  The
 199           kernel will detect this on bootup, and give up.
 200         - A kernel with math-emulation compiled in will still use the
 201           coprocessor if one is present: the math emulation will just
 202           never get used in that case.  The kernel will be slightly larger,
 203           but will work on different machines regardless of whether they
 204           have a math coprocessor or not.
 205         - the "kernel hacking" configuration details usually result in a
 206           bigger or slower kernel (or both), and can even make the kernel
 207           less stable by configuring some routines to actively try to
 208           break bad code to find kernel problems (kmalloc()).  Thus you
 209           should probably answer 'n' to the questions for
 210           "development", "experimental", or "debugging" features.
 211
 212 COMPILING the kernel:
 213
 214  - Make sure you have at least gcc 3.2 available.
 215    For more information, refer to Documentation/Changes.
 216
 217    Please note that you can still run a.out user programs with this kernel.
 218
 219  - Do a "make" to create a compressed kernel image. It is also
 220    possible to do "make install" if you have lilo installed to suit the
 221    kernel makefiles, but you may want to check your particular lilo setup first.
 222
 223    To do the actual install you have to be root, but none of the normal
 224    build should require that. Don't take the name of root in vain.
 225
 226  - If you configured any of the parts of the kernel as `modules', you
 227    will also have to do "make modules_install".
 228
 229  - Verbose kernel compile/build output:
 230
 231    Normally the kernel build system runs in a fairly quiet mode (but not
 232    totally silent).  However, sometimes you or other kernel developers need
 233    to see compile, link, or other commands exactly as they are executed.
 234    For this, use "verbose" build mode.  This is done by inserting
 235    "V=1" in the "make" command.  E.g.:
 236
 237         make V=1 all
 238
 239    To have the build system also tell the reason for the rebuild of each
 240    target, use "V=2".  The default is "V=0".
 241
 242  - Keep a backup kernel handy in case something goes wrong.  This is
 243    especially true for the development releases, since each new release
 244    contains new code which has not been debugged.  Make sure you keep a
 245    backup of the modules corresponding to that kernel, as well.  If you
 246    are installing a new kernel with the same version number as your
 247    working kernel, make a backup of your modules directory before you
 248    do a "make modules_install".
 249    Alternatively, before compiling, use the kernel config option
 250    "LOCALVERSION" to append a unique suffix to the regular kernel version.
 251    LOCALVERSION can be set in the "General Setup" menu.
 252
 253  - In order to boot your new kernel, you'll need to copy the kernel
 254    image (e.g. .../linux/arch/i386/boot/bzImage after compilation)
 255    to the place where your regular bootable kernel is found.
 256
 257  - Booting a kernel directly from a floppy without the assistance of a
 258    bootloader such as LILO, is no longer supported.
 259
 260    If you boot Linux from the hard drive, chances are you use LILO which
 261    uses the kernel image as specified in the file /etc/lilo.conf.  The
 262    kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or
 263    /boot/bzImage.  To use the new kernel, save a copy of the old image
 264    and copy the new image over the old one.  Then, you MUST RERUN LILO
 265    to update the loading map!! If you don't, you won't be able to boot
 266    the new kernel image.
 267
 268    Reinstalling LILO is usually a matter of running /sbin/lilo.
 269    You may wish to edit /etc/lilo.conf to specify an entry for your
 270    old kernel image (say, /vmlinux.old) in case the new one does not
 271    work.  See the LILO docs for more information.
 272
 273    After reinstalling LILO, you should be all set.  Shutdown the system,
 274    reboot, and enjoy!
 275
 276    If you ever need to change the default root device, video mode,
 277    ramdisk size, etc.  in the kernel image, use the 'rdev' program (or
 278    alternatively the LILO boot options when appropriate).  No need to
 279    recompile the kernel to change these parameters.
 280
 281  - Reboot with the new kernel and enjoy.
 282
 283 IF SOMETHING GOES WRONG:
 284
 285  - If you have problems that seem to be due to kernel bugs, please check
 286    the file MAINTAINERS to see if there is a particular person associated
 287    with the part of the kernel that you are having trouble with. If there
 288    isn't anyone listed there, then the second best thing is to mail
 289    them to me (torvalds@linux-foundation.org), and possibly to any other
 290    relevant mailing-list or to the newsgroup.
 291
 292  - In all bug-reports, *please* tell what kernel you are talking about,
 293    how to duplicate the problem, and what your setup is (use your common
 294    sense).  If the problem is new, tell me so, and if the problem is
 295    old, please try to tell me when you first noticed it.
 296
 297  - If the bug results in a message like
 298
 299         unable to handle kernel paging request at address C0000010
 300         Oops: 0002
 301         EIP:   0010:XXXXXXXX
 302         eax: xxxxxxxx   ebx: xxxxxxxx   ecx: xxxxxxxx   edx: xxxxxxxx
 303         esi: xxxxxxxx   edi: xxxxxxxx   ebp: xxxxxxxx
 304         ds: xxxx  es: xxxx  fs: xxxx  gs: xxxx
 305         Pid: xx, process nr: xx
 306         xx xx xx xx xx xx xx xx xx xx
 307
 308    or similar kernel debugging information on your screen or in your
 309    system log, please duplicate it *exactly*.  The dump may look
 310    incomprehensible to you, but it does contain information that may
 311    help debugging the problem.  The text above the dump is also
 312    important: it tells something about why the kernel dumped code (in
 313    the above example it's due to a bad kernel pointer). More information
 314    on making sense of the dump is in Documentation/oops-tracing.txt
 315
 316  - If you compiled the kernel with CONFIG_KALLSYMS you can send the dump
 317    as is, otherwise you will have to use the "ksymoops" program to make
 318    sense of the dump (but compiling with CONFIG_KALLSYMS is usually preferred).
 319    This utility can be downloaded from
 320    ftp://ftp.<country>.kernel.org/pub/linux/utils/kernel/ksymoops/ .
 321    Alternately you can do the dump lookup by hand:
 322
 323  - In debugging dumps like the above, it helps enormously if you can
 324    look up what the EIP value means.  The hex value as such doesn't help
 325    me or anybody else very much: it will depend on your particular
 326    kernel setup.  What you should do is take the hex value from the EIP
 327    line (ignore the "0010:"), and look it up in the kernel namelist to
 328    see which kernel function contains the offending address.
 329
 330    To find out the kernel function name, you'll need to find the system
 331    binary associated with the kernel that exhibited the symptom.  This is
 332    the file 'linux/vmlinux'.  To extract the namelist and match it against
 333    the EIP from the kernel crash, do:
 334
 335                 nm vmlinux | sort | less
 336
 337    This will give you a list of kernel addresses sorted in ascending
 338    order, from which it is simple to find the function that contains the
 339    offending address.  Note that the address given by the kernel
 340    debugging messages will not necessarily match exactly with the
 341    function addresses (in fact, that is very unlikely), so you can't
 342    just 'grep' the list: the list will, however, give you the starting
 343    point of each kernel function, so by looking for the function that
 344    has a starting address lower than the one you are searching for but
 345    is followed by a function with a higher address you will find the one
 346    you want.  In fact, it may be a good idea to include a bit of
 347    "context" in your problem report, giving a few lines around the
 348    interesting one.
 349
 350    If you for some reason cannot do the above (you have a pre-compiled
 351    kernel image or similar), telling me as much about your setup as
 352    possible will help.  Please read the REPORTING-BUGS document for details.
 353
 354  - Alternately, you can use gdb on a running kernel. (read-only; i.e. you
 355    cannot change values or set break points.) To do this, first compile the
 356    kernel with -g; edit arch/i386/Makefile appropriately, then do a "make
 357    clean". You'll also need to enable CONFIG_PROC_FS (via "make config").
 358
 359    After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore".
 360    You can now use all the usual gdb commands. The command to look up the
 361    point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes
 362    with the EIP value.)
 363
 364    gdb'ing a non-running kernel currently fails because gdb (wrongly)
 365    disregards the starting offset for which the kernel is compiled.
 366