linux/README
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   1        Linux kernel release 3.x <http://kernel.org/>
   2
   3These are the release notes for Linux version 3.  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, Tilera TILE, 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-3.X.tar.gz | tar xvf -
  66
  67   or
  68
  69     bzip2 -dc linux-3.X.tar.bz2 | tar xvf -
  70
  71   Replace "X" 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 3.x 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-3.X) and execute:
  82
  83     gzip -cd ../patch-3.x.gz | patch -p1
  84
  85   or
  86
  87     bzip2 -dc ../patch-3.x.bz2 | patch -p1
  88
  89   Replace "x" for all versions bigger than the version "X" of your current
  90   source tree, _in_order_, and you should be ok.  You may want to remove
  91   the backup files (some-file-name~ or some-file-name.orig), and make sure
  92   that there are no failed patches (some-file-name# or some-file-name.rej).
  93   If there are, either you or I have made a mistake.
  94
  95   Unlike patches for the 3.x kernels, patches for the 3.x.y kernels
  96   (also known as the -stable kernels) are not incremental but instead apply
  97   directly to the base 3.x kernel.  For example, if your base kernel is 3.0
  98   and you want to apply the 3.0.3 patch, you must not first apply the 3.0.1
  99   and 3.0.2 patches. Similarly, if you are running kernel version 3.0.2 and
 100   want to jump to 3.0.3, you must first reverse the 3.0.2 patch (that is,
 101   patch -R) _before_ applying the 3.0.3 patch. You can read more on this in
 102   Documentation/applying-patches.txt
 103
 104   Alternatively, the script patch-kernel can be used to automate this
 105   process.  It determines the current kernel version and applies any
 106   patches found.
 107
 108     linux/scripts/patch-kernel linux
 109
 110   The first argument in the command above is the location of the
 111   kernel source.  Patches are applied from the current directory, but
 112   an alternative directory can be specified as the second argument.
 113
 114 - Make sure you have no stale .o files and dependencies lying around:
 115
 116     cd linux
 117     make mrproper
 118
 119   You should now have the sources correctly installed.
 120
 121SOFTWARE REQUIREMENTS
 122
 123   Compiling and running the 3.x kernels requires up-to-date
 124   versions of various software packages.  Consult
 125   Documentation/Changes for the minimum version numbers required
 126   and how to get updates for these packages.  Beware that using
 127   excessively old versions of these packages can cause indirect
 128   errors that are very difficult to track down, so don't assume that
 129   you can just update packages when obvious problems arise during
 130   build or operation.
 131
 132BUILD directory for the kernel:
 133
 134   When compiling the kernel, all output files will per default be
 135   stored together with the kernel source code.
 136   Using the option "make O=output/dir" allow you to specify an alternate
 137   place for the output files (including .config).
 138   Example:
 139
 140     kernel source code: /usr/src/linux-3.X
 141     build directory:    /home/name/build/kernel
 142
 143   To configure and build the kernel, use:
 144
 145     cd /usr/src/linux-3.X
 146     make O=/home/name/build/kernel menuconfig
 147     make O=/home/name/build/kernel
 148     sudo make O=/home/name/build/kernel modules_install install
 149
 150   Please note: If the 'O=output/dir' option is used, then it must be
 151   used for all invocations of make.
 152
 153CONFIGURING the kernel:
 154
 155   Do not skip this step even if you are only upgrading one minor
 156   version.  New configuration options are added in each release, and
 157   odd problems will turn up if the configuration files are not set up
 158   as expected.  If you want to carry your existing configuration to a
 159   new version with minimal work, use "make oldconfig", which will
 160   only ask you for the answers to new questions.
 161
 162 - Alternative configuration commands are:
 163
 164     "make config"      Plain text interface.
 165
 166     "make menuconfig"  Text based color menus, radiolists & dialogs.
 167
 168     "make nconfig"     Enhanced text based color menus.
 169
 170     "make xconfig"     X windows (Qt) based configuration tool.
 171
 172     "make gconfig"     X windows (Gtk) based configuration tool.
 173
 174     "make oldconfig"   Default all questions based on the contents of
 175                        your existing ./.config file and asking about
 176                        new config symbols.
 177
 178     "make silentoldconfig"
 179                        Like above, but avoids cluttering the screen
 180                        with questions already answered.
 181                        Additionally updates the dependencies.
 182
 183     "make defconfig"   Create a ./.config file by using the default
 184                        symbol values from either arch/$ARCH/defconfig
 185                        or arch/$ARCH/configs/${PLATFORM}_defconfig,
 186                        depending on the architecture.
 187
 188     "make ${PLATFORM}_defconfig"
 189                        Create a ./.config file by using the default
 190                        symbol values from
 191                        arch/$ARCH/configs/${PLATFORM}_defconfig.
 192                        Use "make help" to get a list of all available
 193                        platforms of your architecture.
 194
 195     "make allyesconfig"
 196                        Create a ./.config file by setting symbol
 197                        values to 'y' as much as possible.
 198
 199     "make allmodconfig"
 200                        Create a ./.config file by setting symbol
 201                        values to 'm' as much as possible.
 202
 203     "make allnoconfig" Create a ./.config file by setting symbol
 204                        values to 'n' as much as possible.
 205
 206     "make randconfig"  Create a ./.config file by setting symbol
 207                        values to random values.
 208
 209   You can find more information on using the Linux kernel config tools
 210   in Documentation/kbuild/kconfig.txt.
 211
 212 - NOTES on "make config":
 213
 214    - Having unnecessary drivers will make the kernel bigger, and can
 215      under some circumstances lead to problems: probing for a
 216      nonexistent controller card may confuse your other controllers
 217
 218    - Compiling the kernel with "Processor type" set higher than 386
 219      will result in a kernel that does NOT work on a 386.  The
 220      kernel will detect this on bootup, and give up.
 221
 222    - A kernel with math-emulation compiled in will still use the
 223      coprocessor if one is present: the math emulation will just
 224      never get used in that case.  The kernel will be slightly larger,
 225      but will work on different machines regardless of whether they
 226      have a math coprocessor or not.
 227
 228    - The "kernel hacking" configuration details usually result in a
 229      bigger or slower kernel (or both), and can even make the kernel
 230      less stable by configuring some routines to actively try to
 231      break bad code to find kernel problems (kmalloc()).  Thus you
 232      should probably answer 'n' to the questions for "development",
 233      "experimental", or "debugging" features.
 234
 235COMPILING the kernel:
 236
 237 - Make sure you have at least gcc 3.2 available.
 238   For more information, refer to Documentation/Changes.
 239
 240   Please note that you can still run a.out user programs with this kernel.
 241
 242 - Do a "make" to create a compressed kernel image. It is also
 243   possible to do "make install" if you have lilo installed to suit the
 244   kernel makefiles, but you may want to check your particular lilo setup first.
 245
 246   To do the actual install, you have to be root, but none of the normal
 247   build should require that. Don't take the name of root in vain.
 248
 249 - If you configured any of the parts of the kernel as `modules', you
 250   will also have to do "make modules_install".
 251
 252 - Verbose kernel compile/build output:
 253
 254   Normally, the kernel build system runs in a fairly quiet mode (but not
 255   totally silent).  However, sometimes you or other kernel developers need
 256   to see compile, link, or other commands exactly as they are executed.
 257   For this, use "verbose" build mode.  This is done by inserting
 258   "V=1" in the "make" command.  E.g.:
 259
 260     make V=1 all
 261
 262   To have the build system also tell the reason for the rebuild of each
 263   target, use "V=2".  The default is "V=0".
 264
 265 - Keep a backup kernel handy in case something goes wrong.  This is 
 266   especially true for the development releases, since each new release
 267   contains new code which has not been debugged.  Make sure you keep a
 268   backup of the modules corresponding to that kernel, as well.  If you
 269   are installing a new kernel with the same version number as your
 270   working kernel, make a backup of your modules directory before you
 271   do a "make modules_install".
 272
 273   Alternatively, before compiling, use the kernel config option
 274   "LOCALVERSION" to append a unique suffix to the regular kernel version.
 275   LOCALVERSION can be set in the "General Setup" menu.
 276
 277 - In order to boot your new kernel, you'll need to copy the kernel
 278   image (e.g. .../linux/arch/i386/boot/bzImage after compilation)
 279   to the place where your regular bootable kernel is found. 
 280
 281 - Booting a kernel directly from a floppy without the assistance of a
 282   bootloader such as LILO, is no longer supported.
 283
 284   If you boot Linux from the hard drive, chances are you use LILO, which
 285   uses the kernel image as specified in the file /etc/lilo.conf.  The
 286   kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or
 287   /boot/bzImage.  To use the new kernel, save a copy of the old image
 288   and copy the new image over the old one.  Then, you MUST RERUN LILO
 289   to update the loading map!! If you don't, you won't be able to boot
 290   the new kernel image.
 291
 292   Reinstalling LILO is usually a matter of running /sbin/lilo. 
 293   You may wish to edit /etc/lilo.conf to specify an entry for your
 294   old kernel image (say, /vmlinux.old) in case the new one does not
 295   work.  See the LILO docs for more information. 
 296
 297   After reinstalling LILO, you should be all set.  Shutdown the system,
 298   reboot, and enjoy!
 299
 300   If you ever need to change the default root device, video mode,
 301   ramdisk size, etc.  in the kernel image, use the 'rdev' program (or
 302   alternatively the LILO boot options when appropriate).  No need to
 303   recompile the kernel to change these parameters. 
 304
 305 - Reboot with the new kernel and enjoy. 
 306
 307IF SOMETHING GOES WRONG:
 308
 309 - If you have problems that seem to be due to kernel bugs, please check
 310   the file MAINTAINERS to see if there is a particular person associated
 311   with the part of the kernel that you are having trouble with. If there
 312   isn't anyone listed there, then the second best thing is to mail
 313   them to me (torvalds@linux-foundation.org), and possibly to any other
 314   relevant mailing-list or to the newsgroup.
 315
 316 - In all bug-reports, *please* tell what kernel you are talking about,
 317   how to duplicate the problem, and what your setup is (use your common
 318   sense).  If the problem is new, tell me so, and if the problem is
 319   old, please try to tell me when you first noticed it.
 320
 321 - If the bug results in a message like
 322
 323     unable to handle kernel paging request at address C0000010
 324     Oops: 0002
 325     EIP:   0010:XXXXXXXX
 326     eax: xxxxxxxx   ebx: xxxxxxxx   ecx: xxxxxxxx   edx: xxxxxxxx
 327     esi: xxxxxxxx   edi: xxxxxxxx   ebp: xxxxxxxx
 328     ds: xxxx  es: xxxx  fs: xxxx  gs: xxxx
 329     Pid: xx, process nr: xx
 330     xx xx xx xx xx xx xx xx xx xx
 331
 332   or similar kernel debugging information on your screen or in your
 333   system log, please duplicate it *exactly*.  The dump may look
 334   incomprehensible to you, but it does contain information that may
 335   help debugging the problem.  The text above the dump is also
 336   important: it tells something about why the kernel dumped code (in
 337   the above example, it's due to a bad kernel pointer). More information
 338   on making sense of the dump is in Documentation/oops-tracing.txt
 339
 340 - If you compiled the kernel with CONFIG_KALLSYMS you can send the dump
 341   as is, otherwise you will have to use the "ksymoops" program to make
 342   sense of the dump (but compiling with CONFIG_KALLSYMS is usually preferred).
 343   This utility can be downloaded from
 344   ftp://ftp.<country>.kernel.org/pub/linux/utils/kernel/ksymoops/ .
 345   Alternatively, you can do the dump lookup by hand:
 346
 347 - In debugging dumps like the above, it helps enormously if you can
 348   look up what the EIP value means.  The hex value as such doesn't help
 349   me or anybody else very much: it will depend on your particular
 350   kernel setup.  What you should do is take the hex value from the EIP
 351   line (ignore the "0010:"), and look it up in the kernel namelist to
 352   see which kernel function contains the offending address.
 353
 354   To find out the kernel function name, you'll need to find the system
 355   binary associated with the kernel that exhibited the symptom.  This is
 356   the file 'linux/vmlinux'.  To extract the namelist and match it against
 357   the EIP from the kernel crash, do:
 358
 359     nm vmlinux | sort | less
 360
 361   This will give you a list of kernel addresses sorted in ascending
 362   order, from which it is simple to find the function that contains the
 363   offending address.  Note that the address given by the kernel
 364   debugging messages will not necessarily match exactly with the
 365   function addresses (in fact, that is very unlikely), so you can't
 366   just 'grep' the list: the list will, however, give you the starting
 367   point of each kernel function, so by looking for the function that
 368   has a starting address lower than the one you are searching for but
 369   is followed by a function with a higher address you will find the one
 370   you want.  In fact, it may be a good idea to include a bit of
 371   "context" in your problem report, giving a few lines around the
 372   interesting one. 
 373
 374   If you for some reason cannot do the above (you have a pre-compiled
 375   kernel image or similar), telling me as much about your setup as
 376   possible will help.  Please read the REPORTING-BUGS document for details.
 377
 378 - Alternatively, you can use gdb on a running kernel. (read-only; i.e. you
 379   cannot change values or set break points.) To do this, first compile the
 380   kernel with -g; edit arch/i386/Makefile appropriately, then do a "make
 381   clean". You'll also need to enable CONFIG_PROC_FS (via "make config").
 382
 383   After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore".
 384   You can now use all the usual gdb commands. The command to look up the
 385   point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes
 386   with the EIP value.)
 387
 388   gdb'ing a non-running kernel currently fails because gdb (wrongly)
 389   disregards the starting offset for which the kernel is compiled.
 390
 391
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