Root/README

Source at commit be977234bfb4a6dca8a39e7c52165e4cd536ad71 created 9 years 3 months ago.
By Lars-Peter Clausen, jz4740: Fix compile error
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, 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-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 nconfig" Enhanced text based color menus.
170    "make xconfig" X windows (Qt) based configuration tool.
171    "make gconfig" X windows (Gtk) based configuration tool.
172    "make oldconfig" Default all questions based on the contents of
173               your existing ./.config file and asking about
174               new config symbols.
175    "make silentoldconfig"
176               Like above, but avoids cluttering the screen
177               with questions already answered.
178               Additionally updates the dependencies.
179    "make defconfig" Create a ./.config file by using the default
180               symbol values from either arch/$ARCH/defconfig
181               or arch/$ARCH/configs/${PLATFORM}_defconfig,
182               depending on the architecture.
183    "make ${PLATFORM}_defconfig"
184              Create a ./.config file by using the default
185              symbol values from
186              arch/$ARCH/configs/${PLATFORM}_defconfig.
187              Use "make help" to get a list of all available
188              platforms of your architecture.
189    "make allyesconfig"
190               Create a ./.config file by setting symbol
191               values to 'y' as much as possible.
192    "make allmodconfig"
193               Create a ./.config file by setting symbol
194               values to 'm' as much as possible.
195    "make allnoconfig" Create a ./.config file by setting symbol
196               values to 'n' as much as possible.
197    "make randconfig" Create a ./.config file by setting symbol
198               values to random values.
199
200   You can find more information on using the Linux kernel config tools
201   in Documentation/kbuild/kconfig.txt.
202
203    NOTES on "make config":
204    - having unnecessary drivers will make the kernel bigger, and can
205      under some circumstances lead to problems: probing for a
206      nonexistent controller card may confuse your other controllers
207    - compiling the kernel with "Processor type" set higher than 386
208      will result in a kernel that does NOT work on a 386. The
209      kernel will detect this on bootup, and give up.
210    - A kernel with math-emulation compiled in will still use the
211      coprocessor if one is present: the math emulation will just
212      never get used in that case. The kernel will be slightly larger,
213      but will work on different machines regardless of whether they
214      have a math coprocessor or not.
215    - the "kernel hacking" configuration details usually result in a
216      bigger or slower kernel (or both), and can even make the kernel
217      less stable by configuring some routines to actively try to
218      break bad code to find kernel problems (kmalloc()). Thus you
219      should probably answer 'n' to the questions for
220          "development", "experimental", or "debugging" features.
221
222COMPILING the kernel:
223
224 - Make sure you have at least gcc 3.2 available.
225   For more information, refer to Documentation/Changes.
226
227   Please note that you can still run a.out user programs with this kernel.
228
229 - Do a "make" to create a compressed kernel image. It is also
230   possible to do "make install" if you have lilo installed to suit the
231   kernel makefiles, but you may want to check your particular lilo setup first.
232
233   To do the actual install you have to be root, but none of the normal
234   build should require that. Don't take the name of root in vain.
235
236 - If you configured any of the parts of the kernel as `modules', you
237   will also have to do "make modules_install".
238
239 - Verbose kernel compile/build output:
240
241   Normally the kernel build system runs in a fairly quiet mode (but not
242   totally silent). However, sometimes you or other kernel developers need
243   to see compile, link, or other commands exactly as they are executed.
244   For this, use "verbose" build mode. This is done by inserting
245   "V=1" in the "make" command. E.g.:
246
247    make V=1 all
248
249   To have the build system also tell the reason for the rebuild of each
250   target, use "V=2". The default is "V=0".
251
252 - Keep a backup kernel handy in case something goes wrong. This is
253   especially true for the development releases, since each new release
254   contains new code which has not been debugged. Make sure you keep a
255   backup of the modules corresponding to that kernel, as well. If you
256   are installing a new kernel with the same version number as your
257   working kernel, make a backup of your modules directory before you
258   do a "make modules_install".
259   Alternatively, before compiling, use the kernel config option
260   "LOCALVERSION" to append a unique suffix to the regular kernel version.
261   LOCALVERSION can be set in the "General Setup" menu.
262
263 - In order to boot your new kernel, you'll need to copy the kernel
264   image (e.g. .../linux/arch/i386/boot/bzImage after compilation)
265   to the place where your regular bootable kernel is found.
266
267 - Booting a kernel directly from a floppy without the assistance of a
268   bootloader such as LILO, is no longer supported.
269
270   If you boot Linux from the hard drive, chances are you use LILO which
271   uses the kernel image as specified in the file /etc/lilo.conf. The
272   kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or
273   /boot/bzImage. To use the new kernel, save a copy of the old image
274   and copy the new image over the old one. Then, you MUST RERUN LILO
275   to update the loading map!! If you don't, you won't be able to boot
276   the new kernel image.
277
278   Reinstalling LILO is usually a matter of running /sbin/lilo.
279   You may wish to edit /etc/lilo.conf to specify an entry for your
280   old kernel image (say, /vmlinux.old) in case the new one does not
281   work. See the LILO docs for more information.
282
283   After reinstalling LILO, you should be all set. Shutdown the system,
284   reboot, and enjoy!
285
286   If you ever need to change the default root device, video mode,
287   ramdisk size, etc. in the kernel image, use the 'rdev' program (or
288   alternatively the LILO boot options when appropriate). No need to
289   recompile the kernel to change these parameters.
290
291 - Reboot with the new kernel and enjoy.
292
293IF SOMETHING GOES WRONG:
294
295 - If you have problems that seem to be due to kernel bugs, please check
296   the file MAINTAINERS to see if there is a particular person associated
297   with the part of the kernel that you are having trouble with. If there
298   isn't anyone listed there, then the second best thing is to mail
299   them to me (torvalds@linux-foundation.org), and possibly to any other
300   relevant mailing-list or to the newsgroup.
301
302 - In all bug-reports, *please* tell what kernel you are talking about,
303   how to duplicate the problem, and what your setup is (use your common
304   sense). If the problem is new, tell me so, and if the problem is
305   old, please try to tell me when you first noticed it.
306
307 - If the bug results in a message like
308
309    unable to handle kernel paging request at address C0000010
310    Oops: 0002
311    EIP: 0010:XXXXXXXX
312    eax: xxxxxxxx ebx: xxxxxxxx ecx: xxxxxxxx edx: xxxxxxxx
313    esi: xxxxxxxx edi: xxxxxxxx ebp: xxxxxxxx
314    ds: xxxx es: xxxx fs: xxxx gs: xxxx
315    Pid: xx, process nr: xx
316    xx xx xx xx xx xx xx xx xx xx
317
318   or similar kernel debugging information on your screen or in your
319   system log, please duplicate it *exactly*. The dump may look
320   incomprehensible to you, but it does contain information that may
321   help debugging the problem. The text above the dump is also
322   important: it tells something about why the kernel dumped code (in
323   the above example it's due to a bad kernel pointer). More information
324   on making sense of the dump is in Documentation/oops-tracing.txt
325
326 - If you compiled the kernel with CONFIG_KALLSYMS you can send the dump
327   as is, otherwise you will have to use the "ksymoops" program to make
328   sense of the dump (but compiling with CONFIG_KALLSYMS is usually preferred).
329   This utility can be downloaded from
330   ftp://ftp.<country>.kernel.org/pub/linux/utils/kernel/ksymoops/ .
331   Alternately you can do the dump lookup by hand:
332
333 - In debugging dumps like the above, it helps enormously if you can
334   look up what the EIP value means. The hex value as such doesn't help
335   me or anybody else very much: it will depend on your particular
336   kernel setup. What you should do is take the hex value from the EIP
337   line (ignore the "0010:"), and look it up in the kernel namelist to
338   see which kernel function contains the offending address.
339
340   To find out the kernel function name, you'll need to find the system
341   binary associated with the kernel that exhibited the symptom. This is
342   the file 'linux/vmlinux'. To extract the namelist and match it against
343   the EIP from the kernel crash, do:
344
345        nm vmlinux | sort | less
346
347   This will give you a list of kernel addresses sorted in ascending
348   order, from which it is simple to find the function that contains the
349   offending address. Note that the address given by the kernel
350   debugging messages will not necessarily match exactly with the
351   function addresses (in fact, that is very unlikely), so you can't
352   just 'grep' the list: the list will, however, give you the starting
353   point of each kernel function, so by looking for the function that
354   has a starting address lower than the one you are searching for but
355   is followed by a function with a higher address you will find the one
356   you want. In fact, it may be a good idea to include a bit of
357   "context" in your problem report, giving a few lines around the
358   interesting one.
359
360   If you for some reason cannot do the above (you have a pre-compiled
361   kernel image or similar), telling me as much about your setup as
362   possible will help. Please read the REPORTING-BUGS document for details.
363
364 - Alternately, you can use gdb on a running kernel. (read-only; i.e. you
365   cannot change values or set break points.) To do this, first compile the
366   kernel with -g; edit arch/i386/Makefile appropriately, then do a "make
367   clean". You'll also need to enable CONFIG_PROC_FS (via "make config").
368
369   After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore".
370   You can now use all the usual gdb commands. The command to look up the
371   point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes
372   with the EIP value.)
373
374   gdb'ing a non-running kernel currently fails because gdb (wrongly)
375   disregards the starting offset for which the kernel is compiled.
376
377

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