1 Linux kernel release 2.6.xx 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 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 21ON 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 27DOCUMENTATION: 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 49INSTALLING 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 - If you are upgrading between releases using the stable series patches 91 (for example, patch-2.6.xx.y), note that these "dot-releases" are 92 not incremental and must be applied to the 2.6.xx base tree. For 93 example, if your base kernel is 2.6.12 and you want to apply the 94 2.6.12.3 patch, you do not and indeed must not first apply the 95 2.6.12.1 and 2.6.12.2 patches. Similarly, if you are running kernel 96 version 2.6.12.2 and want to jump to 2.6.12.3, you must first 97 reverse the 2.6.12.2 patch (that is, patch -R) _before_ applying 98 the 2.6.12.3 patch. 99 100 - Make sure you have no stale .o files and dependencies lying around: 101 102 cd linux 103 make mrproper 104 105 You should now have the sources correctly installed. 106 107SOFTWARE REQUIREMENTS 108 109 Compiling and running the 2.6.xx kernels requires up-to-date 110 versions of various software packages. Consult 111 Documentation/Changes for the minimum version numbers required 112 and how to get updates for these packages. Beware that using 113 excessively old versions of these packages can cause indirect 114 errors that are very difficult to track down, so don't assume that 115 you can just update packages when obvious problems arise during 116 build or operation. 117 118BUILD directory for the kernel: 119 120 When compiling the kernel all output files will per default be 121 stored together with the kernel source code. 122 Using the option "make O=output/dir" allow you to specify an alternate 123 place for the output files (including .config). 124 Example: 125 kernel source code: /usr/src/linux-2.6.N 126 build directory: /home/name/build/kernel 127 128 To configure and build the kernel use: 129 cd /usr/src/linux-2.6.N 130 make O=/home/name/build/kernel menuconfig 131 make O=/home/name/build/kernel 132 sudo make O=/home/name/build/kernel modules_install install 133 134 Please note: If the 'O=output/dir' option is used then it must be 135 used for all invocations of make. 136 137CONFIGURING the kernel: 138 139 Do not skip this step even if you are only upgrading one minor 140 version. New configuration options are added in each release, and 141 odd problems will turn up if the configuration files are not set up 142 as expected. If you want to carry your existing configuration to a 143 new version with minimal work, use "make oldconfig", which will 144 only ask you for the answers to new questions. 145 146 - Alternate configuration commands are: 147 "make menuconfig" Text based color menus, radiolists & dialogs. 148 "make xconfig" X windows (Qt) based configuration tool. 149 "make gconfig" X windows (Gtk) based configuration tool. 150 "make oldconfig" Default all questions based on the contents of 151 your existing ./.config file. 152 153 NOTES on "make config": 154 - having unnecessary drivers will make the kernel bigger, and can 155 under some circumstances lead to problems: probing for a 156 nonexistent controller card may confuse your other controllers 157 - compiling the kernel with "Processor type" set higher than 386 158 will result in a kernel that does NOT work on a 386. The 159 kernel will detect this on bootup, and give up. 160 - A kernel with math-emulation compiled in will still use the 161 coprocessor if one is present: the math emulation will just 162 never get used in that case. The kernel will be slightly larger, 163 but will work on different machines regardless of whether they 164 have a math coprocessor or not. 165 - the "kernel hacking" configuration details usually result in a 166 bigger or slower kernel (or both), and can even make the kernel 167 less stable by configuring some routines to actively try to 168 break bad code to find kernel problems (kmalloc()). Thus you 169 should probably answer 'n' to the questions for 170 "development", "experimental", or "debugging" features. 171 172 - Check the top Makefile for further site-dependent configuration 173 (default SVGA mode etc). 174 175COMPILING the kernel: 176 177 - Make sure you have gcc 2.95.3 available. 178 gcc 2.91.66 (egcs-1.1.2), and gcc 2.7.2.3 are known to miscompile 179 some parts of the kernel, and are *no longer supported*. 180 Also remember to upgrade your binutils package (for as/ld/nm and company) 181 if necessary. For more information, refer to Documentation/Changes. 182 183 Please note that you can still run a.out user programs with this kernel. 184 185 - Do a "make" to create a compressed kernel image. It is also 186 possible to do "make install" if you have lilo installed to suit the 187 kernel makefiles, but you may want to check your particular lilo setup first. 188 189 To do the actual install you have to be root, but none of the normal 190 build should require that. Don't take the name of root in vain. 191 192 - If you configured any of the parts of the kernel as `modules', you 193 will also have to do "make modules_install". 194 195 - Keep a backup kernel handy in case something goes wrong. This is 196 especially true for the development releases, since each new release 197 contains new code which has not been debugged. Make sure you keep a 198 backup of the modules corresponding to that kernel, as well. If you 199 are installing a new kernel with the same version number as your 200 working kernel, make a backup of your modules directory before you 201 do a "make modules_install". 202 203 - In order to boot your new kernel, you'll need to copy the kernel 204 image (e.g. .../linux/arch/i386/boot/bzImage after compilation) 205 to the place where your regular bootable kernel is found. 206 207 - Booting a kernel directly from a floppy without the assistance of a 208 bootloader such as LILO, is no longer supported. 209 210 If you boot Linux from the hard drive, chances are you use LILO which 211 uses the kernel image as specified in the file /etc/lilo.conf. The 212 kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or 213 /boot/bzImage. To use the new kernel, save a copy of the old image 214 and copy the new image over the old one. Then, you MUST RERUN LILO 215 to update the loading map!! If you don't, you won't be able to boot 216 the new kernel image. 217 218 Reinstalling LILO is usually a matter of running /sbin/lilo. 219 You may wish to edit /etc/lilo.conf to specify an entry for your 220 old kernel image (say, /vmlinux.old) in case the new one does not 221 work. See the LILO docs for more information. 222 223 After reinstalling LILO, you should be all set. Shutdown the system, 224 reboot, and enjoy! 225 226 If you ever need to change the default root device, video mode, 227 ramdisk size, etc. in the kernel image, use the 'rdev' program (or 228 alternatively the LILO boot options when appropriate). No need to 229 recompile the kernel to change these parameters. 230 231 - Reboot with the new kernel and enjoy. 232 233IF SOMETHING GOES WRONG: 234 235 - If you have problems that seem to be due to kernel bugs, please check 236 the file MAINTAINERS to see if there is a particular person associated 237 with the part of the kernel that you are having trouble with. If there 238 isn't anyone listed there, then the second best thing is to mail 239 them to me (torvalds@osdl.org), and possibly to any other relevant 240 mailing-list or to the newsgroup. 241 242 - In all bug-reports, *please* tell what kernel you are talking about, 243 how to duplicate the problem, and what your setup is (use your common 244 sense). If the problem is new, tell me so, and if the problem is 245 old, please try to tell me when you first noticed it. 246 247 - If the bug results in a message like 248 249 unable to handle kernel paging request at address C0000010 250 Oops: 0002 251 EIP: 0010:XXXXXXXX 252 eax: xxxxxxxx ebx: xxxxxxxx ecx: xxxxxxxx edx: xxxxxxxx 253 esi: xxxxxxxx edi: xxxxxxxx ebp: xxxxxxxx 254 ds: xxxx es: xxxx fs: xxxx gs: xxxx 255 Pid: xx, process nr: xx 256 xx xx xx xx xx xx xx xx xx xx 257 258 or similar kernel debugging information on your screen or in your 259 system log, please duplicate it *exactly*. The dump may look 260 incomprehensible to you, but it does contain information that may 261 help debugging the problem. The text above the dump is also 262 important: it tells something about why the kernel dumped code (in 263 the above example it's due to a bad kernel pointer). More information 264 on making sense of the dump is in Documentation/oops-tracing.txt 265 266 - If you compiled the kernel with CONFIG_KALLSYMS you can send the dump 267 as is, otherwise you will have to use the "ksymoops" program to make 268 sense of the dump. This utility can be downloaded from 269 ftp://ftp.<country>.kernel.org/pub/linux/utils/kernel/ksymoops. 270 Alternately you can do the dump lookup by hand: 271 272 - In debugging dumps like the above, it helps enormously if you can 273 look up what the EIP value means. The hex value as such doesn't help 274 me or anybody else very much: it will depend on your particular 275 kernel setup. What you should do is take the hex value from the EIP 276 line (ignore the "0010:"), and look it up in the kernel namelist to 277 see which kernel function contains the offending address. 278 279 To find out the kernel function name, you'll need to find the system 280 binary associated with the kernel that exhibited the symptom. This is 281 the file 'linux/vmlinux'. To extract the namelist and match it against 282 the EIP from the kernel crash, do: 283 284 nm vmlinux | sort | less 285 286 This will give you a list of kernel addresses sorted in ascending 287 order, from which it is simple to find the function that contains the 288 offending address. Note that the address given by the kernel 289 debugging messages will not necessarily match exactly with the 290 function addresses (in fact, that is very unlikely), so you can't 291 just 'grep' the list: the list will, however, give you the starting 292 point of each kernel function, so by looking for the function that 293 has a starting address lower than the one you are searching for but 294 is followed by a function with a higher address you will find the one 295 you want. In fact, it may be a good idea to include a bit of 296 "context" in your problem report, giving a few lines around the 297 interesting one. 298 299 If you for some reason cannot do the above (you have a pre-compiled 300 kernel image or similar), telling me as much about your setup as 301 possible will help. 302 303 - Alternately, you can use gdb on a running kernel. (read-only; i.e. you 304 cannot change values or set break points.) To do this, first compile the 305 kernel with -g; edit arch/i386/Makefile appropriately, then do a "make 306 clean". You'll also need to enable CONFIG_PROC_FS (via "make config"). 307 308 After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore". 309 You can now use all the usual gdb commands. The command to look up the 310 point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes 311 with the EIP value.) 312 313 gdb'ing a non-running kernel currently fails because gdb (wrongly) 314 disregards the starting offset for which the kernel is compiled. 315 316