1 Linux kernel !! 1 Linux kernel release 2.6.xx <http://kernel.org/>
2 ============ <<
3 2
4 There are several guides for kernel developers !! 3 These are the release notes for Linux version 2.6. Read them carefully,
5 be rendered in a number of formats, like HTML !! 4 as they tell you what this is all about, explain how to install the
6 Documentation/admin-guide/README.rst first. !! 5 kernel, and what to do if something goes wrong.
7 6
8 In order to build the documentation, use ``mak !! 7 WHAT IS LINUX?
9 ``make pdfdocs``. The formatted documentation <<
10 8
11 https://www.kernel.org/doc/html/latest/ !! 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 12
13 There are various text files in the Documentat !! 13 It has all the features you would expect in a modern fully-fledged Unix,
14 several of them using the reStructuredText mar !! 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 Additionally updates the dependencies.
>> 178 "make defconfig" Create a ./.config file by using the default
>> 179 symbol values from either arch/$ARCH/defconfig
>> 180 or arch/$ARCH/configs/${PLATFORM}_defconfig,
>> 181 depending on the architecture.
>> 182 "make ${PLATFORM}_defconfig"
>> 183 Create a ./.config file by using the default
>> 184 symbol values from
>> 185 arch/$ARCH/configs/${PLATFORM}_defconfig.
>> 186 Use "make help" to get a list of all available
>> 187 platforms of your architecture.
>> 188 "make allyesconfig"
>> 189 Create a ./.config file by setting symbol
>> 190 values to 'y' as much as possible.
>> 191 "make allmodconfig"
>> 192 Create a ./.config file by setting symbol
>> 193 values to 'm' as much as possible.
>> 194 "make allnoconfig" Create a ./.config file by setting symbol
>> 195 values to 'n' as much as possible.
>> 196 "make randconfig" Create a ./.config file by setting symbol
>> 197 values to random values.
>> 198
>> 199 You can find more information on using the Linux kernel config tools
>> 200 in Documentation/kbuild/kconfig.txt.
>> 201
>> 202 NOTES on "make config":
>> 203 - having unnecessary drivers will make the kernel bigger, and can
>> 204 under some circumstances lead to problems: probing for a
>> 205 nonexistent controller card may confuse your other controllers
>> 206 - compiling the kernel with "Processor type" set higher than 386
>> 207 will result in a kernel that does NOT work on a 386. The
>> 208 kernel will detect this on bootup, and give up.
>> 209 - A kernel with math-emulation compiled in will still use the
>> 210 coprocessor if one is present: the math emulation will just
>> 211 never get used in that case. The kernel will be slightly larger,
>> 212 but will work on different machines regardless of whether they
>> 213 have a math coprocessor or not.
>> 214 - the "kernel hacking" configuration details usually result in a
>> 215 bigger or slower kernel (or both), and can even make the kernel
>> 216 less stable by configuring some routines to actively try to
>> 217 break bad code to find kernel problems (kmalloc()). Thus you
>> 218 should probably answer 'n' to the questions for
>> 219 "development", "experimental", or "debugging" features.
>> 220
>> 221 COMPILING the kernel:
>> 222
>> 223 - Make sure you have at least gcc 3.2 available.
>> 224 For more information, refer to Documentation/Changes.
>> 225
>> 226 Please note that you can still run a.out user programs with this kernel.
>> 227
>> 228 - Do a "make" to create a compressed kernel image. It is also
>> 229 possible to do "make install" if you have lilo installed to suit the
>> 230 kernel makefiles, but you may want to check your particular lilo setup first.
>> 231
>> 232 To do the actual install you have to be root, but none of the normal
>> 233 build should require that. Don't take the name of root in vain.
>> 234
>> 235 - If you configured any of the parts of the kernel as `modules', you
>> 236 will also have to do "make modules_install".
>> 237
>> 238 - Verbose kernel compile/build output:
>> 239
>> 240 Normally the kernel build system runs in a fairly quiet mode (but not
>> 241 totally silent). However, sometimes you or other kernel developers need
>> 242 to see compile, link, or other commands exactly as they are executed.
>> 243 For this, use "verbose" build mode. This is done by inserting
>> 244 "V=1" in the "make" command. E.g.:
>> 245
>> 246 make V=1 all
>> 247
>> 248 To have the build system also tell the reason for the rebuild of each
>> 249 target, use "V=2". The default is "V=0".
>> 250
>> 251 - Keep a backup kernel handy in case something goes wrong. This is
>> 252 especially true for the development releases, since each new release
>> 253 contains new code which has not been debugged. Make sure you keep a
>> 254 backup of the modules corresponding to that kernel, as well. If you
>> 255 are installing a new kernel with the same version number as your
>> 256 working kernel, make a backup of your modules directory before you
>> 257 do a "make modules_install".
>> 258 Alternatively, before compiling, use the kernel config option
>> 259 "LOCALVERSION" to append a unique suffix to the regular kernel version.
>> 260 LOCALVERSION can be set in the "General Setup" menu.
>> 261
>> 262 - In order to boot your new kernel, you'll need to copy the kernel
>> 263 image (e.g. .../linux/arch/i386/boot/bzImage after compilation)
>> 264 to the place where your regular bootable kernel is found.
>> 265
>> 266 - Booting a kernel directly from a floppy without the assistance of a
>> 267 bootloader such as LILO, is no longer supported.
>> 268
>> 269 If you boot Linux from the hard drive, chances are you use LILO which
>> 270 uses the kernel image as specified in the file /etc/lilo.conf. The
>> 271 kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or
>> 272 /boot/bzImage. To use the new kernel, save a copy of the old image
>> 273 and copy the new image over the old one. Then, you MUST RERUN LILO
>> 274 to update the loading map!! If you don't, you won't be able to boot
>> 275 the new kernel image.
>> 276
>> 277 Reinstalling LILO is usually a matter of running /sbin/lilo.
>> 278 You may wish to edit /etc/lilo.conf to specify an entry for your
>> 279 old kernel image (say, /vmlinux.old) in case the new one does not
>> 280 work. See the LILO docs for more information.
>> 281
>> 282 After reinstalling LILO, you should be all set. Shutdown the system,
>> 283 reboot, and enjoy!
>> 284
>> 285 If you ever need to change the default root device, video mode,
>> 286 ramdisk size, etc. in the kernel image, use the 'rdev' program (or
>> 287 alternatively the LILO boot options when appropriate). No need to
>> 288 recompile the kernel to change these parameters.
>> 289
>> 290 - Reboot with the new kernel and enjoy.
>> 291
>> 292 IF SOMETHING GOES WRONG:
>> 293
>> 294 - If you have problems that seem to be due to kernel bugs, please check
>> 295 the file MAINTAINERS to see if there is a particular person associated
>> 296 with the part of the kernel that you are having trouble with. If there
>> 297 isn't anyone listed there, then the second best thing is to mail
>> 298 them to me (torvalds@linux-foundation.org), and possibly to any other
>> 299 relevant mailing-list or to the newsgroup.
>> 300
>> 301 - In all bug-reports, *please* tell what kernel you are talking about,
>> 302 how to duplicate the problem, and what your setup is (use your common
>> 303 sense). If the problem is new, tell me so, and if the problem is
>> 304 old, please try to tell me when you first noticed it.
>> 305
>> 306 - If the bug results in a message like
>> 307
>> 308 unable to handle kernel paging request at address C0000010
>> 309 Oops: 0002
>> 310 EIP: 0010:XXXXXXXX
>> 311 eax: xxxxxxxx ebx: xxxxxxxx ecx: xxxxxxxx edx: xxxxxxxx
>> 312 esi: xxxxxxxx edi: xxxxxxxx ebp: xxxxxxxx
>> 313 ds: xxxx es: xxxx fs: xxxx gs: xxxx
>> 314 Pid: xx, process nr: xx
>> 315 xx xx xx xx xx xx xx xx xx xx
>> 316
>> 317 or similar kernel debugging information on your screen or in your
>> 318 system log, please duplicate it *exactly*. The dump may look
>> 319 incomprehensible to you, but it does contain information that may
>> 320 help debugging the problem. The text above the dump is also
>> 321 important: it tells something about why the kernel dumped code (in
>> 322 the above example it's due to a bad kernel pointer). More information
>> 323 on making sense of the dump is in Documentation/oops-tracing.txt
>> 324
>> 325 - If you compiled the kernel with CONFIG_KALLSYMS you can send the dump
>> 326 as is, otherwise you will have to use the "ksymoops" program to make
>> 327 sense of the dump (but compiling with CONFIG_KALLSYMS is usually preferred).
>> 328 This utility can be downloaded from
>> 329 ftp://ftp.<country>.kernel.org/pub/linux/utils/kernel/ksymoops/ .
>> 330 Alternately you can do the dump lookup by hand:
>> 331
>> 332 - In debugging dumps like the above, it helps enormously if you can
>> 333 look up what the EIP value means. The hex value as such doesn't help
>> 334 me or anybody else very much: it will depend on your particular
>> 335 kernel setup. What you should do is take the hex value from the EIP
>> 336 line (ignore the "0010:"), and look it up in the kernel namelist to
>> 337 see which kernel function contains the offending address.
>> 338
>> 339 To find out the kernel function name, you'll need to find the system
>> 340 binary associated with the kernel that exhibited the symptom. This is
>> 341 the file 'linux/vmlinux'. To extract the namelist and match it against
>> 342 the EIP from the kernel crash, do:
>> 343
>> 344 nm vmlinux | sort | less
>> 345
>> 346 This will give you a list of kernel addresses sorted in ascending
>> 347 order, from which it is simple to find the function that contains the
>> 348 offending address. Note that the address given by the kernel
>> 349 debugging messages will not necessarily match exactly with the
>> 350 function addresses (in fact, that is very unlikely), so you can't
>> 351 just 'grep' the list: the list will, however, give you the starting
>> 352 point of each kernel function, so by looking for the function that
>> 353 has a starting address lower than the one you are searching for but
>> 354 is followed by a function with a higher address you will find the one
>> 355 you want. In fact, it may be a good idea to include a bit of
>> 356 "context" in your problem report, giving a few lines around the
>> 357 interesting one.
>> 358
>> 359 If you for some reason cannot do the above (you have a pre-compiled
>> 360 kernel image or similar), telling me as much about your setup as
>> 361 possible will help. Please read the REPORTING-BUGS document for details.
>> 362
>> 363 - Alternately, you can use gdb on a running kernel. (read-only; i.e. you
>> 364 cannot change values or set break points.) To do this, first compile the
>> 365 kernel with -g; edit arch/i386/Makefile appropriately, then do a "make
>> 366 clean". You'll also need to enable CONFIG_PROC_FS (via "make config").
>> 367
>> 368 After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore".
>> 369 You can now use all the usual gdb commands. The command to look up the
>> 370 point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes
>> 371 with the EIP value.)
>> 372
>> 373 gdb'ing a non-running kernel currently fails because gdb (wrongly)
>> 374 disregards the starting offset for which the kernel is compiled.
15 375
16 Please read the Documentation/process/changes. <<
17 requirements for building and running the kern <<
18 the problems which may result by upgrading you <<
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