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1 | Linux kernel release 2.6.xx |
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 Unix clone written from scratch by Linus Torvalds with | |
10 | assistance from a loosely-knit team of hackers across the Net. | |
11 | It aims towards POSIX compliance. | |
12 | ||
13 | It has all the features you would expect in a modern fully-fledged | |
14 | Unix, including true multitasking, virtual memory, shared libraries, | |
15 | demand loading, shared copy-on-write executables, proper memory | |
16 | management and TCP/IP networking. | |
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 | Linux was first developed for 386/486-based PCs. These days it also | |
24 | runs on ARMs, DEC Alphas, SUN Sparcs, M68000 machines (like Atari and | |
25 | Amiga), MIPS and PowerPC, and others. | |
26 | ||
27 | DOCUMENTATION: | |
28 | ||
29 | - There is a lot of documentation available both in electronic form on | |
30 | the Internet and in books, both Linux-specific and pertaining to | |
31 | general UNIX questions. I'd recommend looking into the documentation | |
32 | subdirectories on any Linux FTP site for the LDP (Linux Documentation | |
33 | Project) books. This README is not meant to be documentation on the | |
34 | system: there are much better sources available. | |
35 | ||
36 | - There are various README files in the Documentation/ subdirectory: | |
37 | these typically contain kernel-specific installation notes for some | |
38 | drivers for example. See Documentation/00-INDEX for a list of what | |
39 | is contained in each file. Please read the Changes file, as it | |
40 | contains information about the problems, which may result by upgrading | |
41 | your kernel. | |
42 | ||
43 | - The Documentation/DocBook/ subdirectory contains several guides for | |
44 | kernel developers and users. These guides can be rendered in a | |
45 | number of formats: PostScript (.ps), PDF, and HTML, among others. | |
46 | After installation, "make psdocs", "make pdfdocs", or "make htmldocs" | |
47 | will render the documentation in the requested format. | |
48 | ||
49 | INSTALLING the kernel: | |
50 | ||
51 | - If you install the full sources, put the kernel tarball in a | |
52 | directory where you have permissions (eg. your home directory) and | |
53 | unpack it: | |
54 | ||
55 | gzip -cd linux-2.6.XX.tar.gz | tar xvf - | |
56 | ||
57 | Replace "XX" with the version number of the latest kernel. | |
58 | ||
59 | Do NOT use the /usr/src/linux area! This area has a (usually | |
60 | incomplete) set of kernel headers that are used by the library header | |
61 | files. They should match the library, and not get messed up by | |
62 | whatever the kernel-du-jour happens to be. | |
63 | ||
64 | - You can also upgrade between 2.6.xx releases by patching. Patches are | |
65 | distributed in the traditional gzip and the new bzip2 format. To | |
66 | install by patching, get all the newer patch files, enter the | |
67 | top level directory of the kernel source (linux-2.6.xx) and execute: | |
68 | ||
69 | gzip -cd ../patch-2.6.xx.gz | patch -p1 | |
70 | ||
71 | or | |
72 | bzip2 -dc ../patch-2.6.xx.bz2 | patch -p1 | |
73 | ||
74 | (repeat xx for all versions bigger than the version of your current | |
75 | source tree, _in_order_) and you should be ok. You may want to remove | |
76 | the backup files (xxx~ or xxx.orig), and make sure that there are no | |
77 | failed patches (xxx# or xxx.rej). If there are, either you or me has | |
78 | made a mistake. | |
79 | ||
80 | Alternatively, the script patch-kernel can be used to automate this | |
81 | process. It determines the current kernel version and applies any | |
82 | patches found. | |
83 | ||
84 | linux/scripts/patch-kernel linux | |
85 | ||
86 | The first argument in the command above is the location of the | |
87 | kernel source. Patches are applied from the current directory, but | |
88 | an alternative directory can be specified as the second argument. | |
89 | ||
90 | - Make sure you have no stale .o files and dependencies lying around: | |
91 | ||
92 | cd linux | |
93 | make mrproper | |
94 | ||
95 | You should now have the sources correctly installed. | |
96 | ||
97 | SOFTWARE REQUIREMENTS | |
98 | ||
99 | Compiling and running the 2.6.xx kernels requires up-to-date | |
100 | versions of various software packages. Consult | |
101 | Documentation/Changes for the minimum version numbers required | |
102 | and how to get updates for these packages. Beware that using | |
103 | excessively old versions of these packages can cause indirect | |
104 | errors that are very difficult to track down, so don't assume that | |
105 | you can just update packages when obvious problems arise during | |
106 | build or operation. | |
107 | ||
108 | BUILD directory for the kernel: | |
109 | ||
110 | When compiling the kernel all output files will per default be | |
111 | stored together with the kernel source code. | |
112 | Using the option "make O=output/dir" allow you to specify an alternate | |
113 | place for the output files (including .config). | |
114 | Example: | |
115 | kernel source code: /usr/src/linux-2.6.N | |
116 | build directory: /home/name/build/kernel | |
117 | ||
118 | To configure and build the kernel use: | |
119 | cd /usr/src/linux-2.6.N | |
120 | make O=/home/name/build/kernel menuconfig | |
121 | make O=/home/name/build/kernel | |
122 | sudo make O=/home/name/build/kernel modules_install install | |
123 | ||
124 | Please note: If the 'O=output/dir' option is used then it must be | |
125 | used for all invocations of make. | |
126 | ||
127 | CONFIGURING the kernel: | |
128 | ||
129 | Do not skip this step even if you are only upgrading one minor | |
130 | version. New configuration options are added in each release, and | |
131 | odd problems will turn up if the configuration files are not set up | |
132 | as expected. If you want to carry your existing configuration to a | |
133 | new version with minimal work, use "make oldconfig", which will | |
134 | only ask you for the answers to new questions. | |
135 | ||
136 | - Alternate configuration commands are: | |
137 | "make menuconfig" Text based color menus, radiolists & dialogs. | |
138 | "make xconfig" X windows (Qt) based configuration tool. | |
139 | "make gconfig" X windows (Gtk) based configuration tool. | |
140 | "make oldconfig" Default all questions based on the contents of | |
141 | your existing ./.config file. | |
142 | ||
143 | NOTES on "make config": | |
144 | - having unnecessary drivers will make the kernel bigger, and can | |
145 | under some circumstances lead to problems: probing for a | |
146 | nonexistent controller card may confuse your other controllers | |
147 | - compiling the kernel with "Processor type" set higher than 386 | |
148 | will result in a kernel that does NOT work on a 386. The | |
149 | kernel will detect this on bootup, and give up. | |
150 | - A kernel with math-emulation compiled in will still use the | |
151 | coprocessor if one is present: the math emulation will just | |
152 | never get used in that case. The kernel will be slightly larger, | |
153 | but will work on different machines regardless of whether they | |
154 | have a math coprocessor or not. | |
155 | - the "kernel hacking" configuration details usually result in a | |
156 | bigger or slower kernel (or both), and can even make the kernel | |
157 | less stable by configuring some routines to actively try to | |
158 | break bad code to find kernel problems (kmalloc()). Thus you | |
159 | should probably answer 'n' to the questions for | |
160 | "development", "experimental", or "debugging" features. | |
161 | ||
162 | - Check the top Makefile for further site-dependent configuration | |
163 | (default SVGA mode etc). | |
164 | ||
165 | COMPILING the kernel: | |
166 | ||
167 | - Make sure you have gcc 2.95.3 available. | |
168 | gcc 2.91.66 (egcs-1.1.2), and gcc 2.7.2.3 are known to miscompile | |
169 | some parts of the kernel, and are *no longer supported*. | |
170 | Also remember to upgrade your binutils package (for as/ld/nm and company) | |
171 | if necessary. For more information, refer to Documentation/Changes. | |
172 | ||
173 | Please note that you can still run a.out user programs with this kernel. | |
174 | ||
175 | - Do a "make" to create a compressed kernel image. It is also | |
176 | possible to do "make install" if you have lilo installed to suit the | |
177 | kernel makefiles, but you may want to check your particular lilo setup first. | |
178 | ||
179 | To do the actual install you have to be root, but none of the normal | |
180 | build should require that. Don't take the name of root in vain. | |
181 | ||
182 | - If you configured any of the parts of the kernel as `modules', you | |
183 | will also have to do "make modules_install". | |
184 | ||
185 | - Keep a backup kernel handy in case something goes wrong. This is | |
186 | especially true for the development releases, since each new release | |
187 | contains new code which has not been debugged. Make sure you keep a | |
188 | backup of the modules corresponding to that kernel, as well. If you | |
189 | are installing a new kernel with the same version number as your | |
190 | working kernel, make a backup of your modules directory before you | |
191 | do a "make modules_install". | |
192 | ||
193 | - In order to boot your new kernel, you'll need to copy the kernel | |
194 | image (e.g. .../linux/arch/i386/boot/bzImage after compilation) | |
195 | to the place where your regular bootable kernel is found. | |
196 | ||
197 | - Booting a kernel directly from a floppy without the assistance of a | |
198 | bootloader such as LILO, is no longer supported. | |
199 | ||
200 | If you boot Linux from the hard drive, chances are you use LILO which | |
201 | uses the kernel image as specified in the file /etc/lilo.conf. The | |
202 | kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or | |
203 | /boot/bzImage. To use the new kernel, save a copy of the old image | |
204 | and copy the new image over the old one. Then, you MUST RERUN LILO | |
205 | to update the loading map!! If you don't, you won't be able to boot | |
206 | the new kernel image. | |
207 | ||
208 | Reinstalling LILO is usually a matter of running /sbin/lilo. | |
209 | You may wish to edit /etc/lilo.conf to specify an entry for your | |
210 | old kernel image (say, /vmlinux.old) in case the new one does not | |
211 | work. See the LILO docs for more information. | |
212 | ||
213 | After reinstalling LILO, you should be all set. Shutdown the system, | |
214 | reboot, and enjoy! | |
215 | ||
216 | If you ever need to change the default root device, video mode, | |
217 | ramdisk size, etc. in the kernel image, use the 'rdev' program (or | |
218 | alternatively the LILO boot options when appropriate). No need to | |
219 | recompile the kernel to change these parameters. | |
220 | ||
221 | - Reboot with the new kernel and enjoy. | |
222 | ||
223 | IF SOMETHING GOES WRONG: | |
224 | ||
225 | - If you have problems that seem to be due to kernel bugs, please check | |
226 | the file MAINTAINERS to see if there is a particular person associated | |
227 | with the part of the kernel that you are having trouble with. If there | |
228 | isn't anyone listed there, then the second best thing is to mail | |
229 | them to me (torvalds@osdl.org), and possibly to any other relevant | |
230 | mailing-list or to the newsgroup. | |
231 | ||
232 | - In all bug-reports, *please* tell what kernel you are talking about, | |
233 | how to duplicate the problem, and what your setup is (use your common | |
234 | sense). If the problem is new, tell me so, and if the problem is | |
235 | old, please try to tell me when you first noticed it. | |
236 | ||
237 | - If the bug results in a message like | |
238 | ||
239 | unable to handle kernel paging request at address C0000010 | |
240 | Oops: 0002 | |
241 | EIP: 0010:XXXXXXXX | |
242 | eax: xxxxxxxx ebx: xxxxxxxx ecx: xxxxxxxx edx: xxxxxxxx | |
243 | esi: xxxxxxxx edi: xxxxxxxx ebp: xxxxxxxx | |
244 | ds: xxxx es: xxxx fs: xxxx gs: xxxx | |
245 | Pid: xx, process nr: xx | |
246 | xx xx xx xx xx xx xx xx xx xx | |
247 | ||
248 | or similar kernel debugging information on your screen or in your | |
249 | system log, please duplicate it *exactly*. The dump may look | |
250 | incomprehensible to you, but it does contain information that may | |
251 | help debugging the problem. The text above the dump is also | |
252 | important: it tells something about why the kernel dumped code (in | |
253 | the above example it's due to a bad kernel pointer). More information | |
254 | on making sense of the dump is in Documentation/oops-tracing.txt | |
255 | ||
256 | - If you compiled the kernel with CONFIG_KALLSYMS you can send the dump | |
257 | as is, otherwise you will have to use the "ksymoops" program to make | |
258 | sense of the dump. This utility can be downloaded from | |
259 | ftp://ftp.<country>.kernel.org/pub/linux/utils/kernel/ksymoops. | |
260 | Alternately you can do the dump lookup by hand: | |
261 | ||
262 | - In debugging dumps like the above, it helps enormously if you can | |
263 | look up what the EIP value means. The hex value as such doesn't help | |
264 | me or anybody else very much: it will depend on your particular | |
265 | kernel setup. What you should do is take the hex value from the EIP | |
266 | line (ignore the "0010:"), and look it up in the kernel namelist to | |
267 | see which kernel function contains the offending address. | |
268 | ||
269 | To find out the kernel function name, you'll need to find the system | |
270 | binary associated with the kernel that exhibited the symptom. This is | |
271 | the file 'linux/vmlinux'. To extract the namelist and match it against | |
272 | the EIP from the kernel crash, do: | |
273 | ||
274 | nm vmlinux | sort | less | |
275 | ||
276 | This will give you a list of kernel addresses sorted in ascending | |
277 | order, from which it is simple to find the function that contains the | |
278 | offending address. Note that the address given by the kernel | |
279 | debugging messages will not necessarily match exactly with the | |
280 | function addresses (in fact, that is very unlikely), so you can't | |
281 | just 'grep' the list: the list will, however, give you the starting | |
282 | point of each kernel function, so by looking for the function that | |
283 | has a starting address lower than the one you are searching for but | |
284 | is followed by a function with a higher address you will find the one | |
285 | you want. In fact, it may be a good idea to include a bit of | |
286 | "context" in your problem report, giving a few lines around the | |
287 | interesting one. | |
288 | ||
289 | If you for some reason cannot do the above (you have a pre-compiled | |
290 | kernel image or similar), telling me as much about your setup as | |
291 | possible will help. | |
292 | ||
293 | - Alternately, you can use gdb on a running kernel. (read-only; i.e. you | |
294 | cannot change values or set break points.) To do this, first compile the | |
295 | kernel with -g; edit arch/i386/Makefile appropriately, then do a "make | |
296 | clean". You'll also need to enable CONFIG_PROC_FS (via "make config"). | |
297 | ||
298 | After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore". | |
299 | You can now use all the usual gdb commands. The command to look up the | |
300 | point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes | |
301 | with the EIP value.) | |
302 | ||
303 | gdb'ing a non-running kernel currently fails because gdb (wrongly) | |
304 | disregards the starting offset for which the kernel is compiled. | |
305 |