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   1        Linux kernel release 2.6.xx <http://kernel.org/>
   2
   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. 
   6
   7WHAT 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
  21ON 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
  37DOCUMENTATION:
  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
  59INSTALLING 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
 127SOFTWARE 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
 138BUILD 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
 157CONFIGURING 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
 212COMPILING 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
 283IF 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
 367
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