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 "make silentoldconfig" 153 Like above, but avoids cluttering the screen 154 with questions already answered. 155 156 NOTES on "make config": 157 - having unnecessary drivers will make the kernel bigger, and can 158 under some circumstances lead to problems: probing for a 159 nonexistent controller card may confuse your other controllers 160 - compiling the kernel with "Processor type" set higher than 386 161 will result in a kernel that does NOT work on a 386. The 162 kernel will detect this on bootup, and give up. 163 - A kernel with math-emulation compiled in will still use the 164 coprocessor if one is present: the math emulation will just 165 never get used in that case. The kernel will be slightly larger, 166 but will work on different machines regardless of whether they 167 have a math coprocessor or not. 168 - the "kernel hacking" configuration details usually result in a 169 bigger or slower kernel (or both), and can even make the kernel 170 less stable by configuring some routines to actively try to 171 break bad code to find kernel problems (kmalloc()). Thus you 172 should probably answer 'n' to the questions for 173 "development", "experimental", or "debugging" features. 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 Alternatively, before compiling, use the kernel config option 203 "LOCALVERSION" to append a unique suffix to the regular kernel version. 204 LOCALVERSION can be set in the "General Setup" menu. 205 206 - In order to boot your new kernel, you'll need to copy the kernel 207 image (e.g. .../linux/arch/i386/boot/bzImage after compilation) 208 to the place where your regular bootable kernel is found. 209 210 - Booting a kernel directly from a floppy without the assistance of a 211 bootloader such as LILO, is no longer supported. 212 213 If you boot Linux from the hard drive, chances are you use LILO which 214 uses the kernel image as specified in the file /etc/lilo.conf. The 215 kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or 216 /boot/bzImage. To use the new kernel, save a copy of the old image 217 and copy the new image over the old one. Then, you MUST RERUN LILO 218 to update the loading map!! If you don't, you won't be able to boot 219 the new kernel image. 220 221 Reinstalling LILO is usually a matter of running /sbin/lilo. 222 You may wish to edit /etc/lilo.conf to specify an entry for your 223 old kernel image (say, /vmlinux.old) in case the new one does not 224 work. See the LILO docs for more information. 225 226 After reinstalling LILO, you should be all set. Shutdown the system, 227 reboot, and enjoy! 228 229 If you ever need to change the default root device, video mode, 230 ramdisk size, etc. in the kernel image, use the 'rdev' program (or 231 alternatively the LILO boot options when appropriate). No need to 232 recompile the kernel to change these parameters. 233 234 - Reboot with the new kernel and enjoy. 235 236IF SOMETHING GOES WRONG: 237 238 - If you have problems that seem to be due to kernel bugs, please check 239 the file MAINTAINERS to see if there is a particular person associated 240 with the part of the kernel that you are having trouble with. If there 241 isn't anyone listed there, then the second best thing is to mail 242 them to me (torvalds@osdl.org), and possibly to any other relevant 243 mailing-list or to the newsgroup. 244 245 - In all bug-reports, *please* tell what kernel you are talking about, 246 how to duplicate the problem, and what your setup is (use your common 247 sense). If the problem is new, tell me so, and if the problem is 248 old, please try to tell me when you first noticed it. 249 250 - If the bug results in a message like 251 252 unable to handle kernel paging request at address C0000010 253 Oops: 0002 254 EIP: 0010:XXXXXXXX 255 eax: xxxxxxxx ebx: xxxxxxxx ecx: xxxxxxxx edx: xxxxxxxx 256 esi: xxxxxxxx edi: xxxxxxxx ebp: xxxxxxxx 257 ds: xxxx es: xxxx fs: xxxx gs: xxxx 258 Pid: xx, process nr: xx 259 xx xx xx xx xx xx xx xx xx xx 260 261 or similar kernel debugging information on your screen or in your 262 system log, please duplicate it *exactly*. The dump may look 263 incomprehensible to you, but it does contain information that may 264 help debugging the problem. The text above the dump is also 265 important: it tells something about why the kernel dumped code (in 266 the above example it's due to a bad kernel pointer). More information 267 on making sense of the dump is in Documentation/oops-tracing.txt 268 269 - If you compiled the kernel with CONFIG_KALLSYMS you can send the dump 270 as is, otherwise you will have to use the "ksymoops" program to make 271 sense of the dump. This utility can be downloaded from 272 ftp://ftp.<country>.kernel.org/pub/linux/utils/kernel/ksymoops. 273 Alternately you can do the dump lookup by hand: 274 275 - In debugging dumps like the above, it helps enormously if you can 276 look up what the EIP value means. The hex value as such doesn't help 277 me or anybody else very much: it will depend on your particular 278 kernel setup. What you should do is take the hex value from the EIP 279 line (ignore the "0010:"), and look it up in the kernel namelist to 280 see which kernel function contains the offending address. 281 282 To find out the kernel function name, you'll need to find the system 283 binary associated with the kernel that exhibited the symptom. This is 284 the file 'linux/vmlinux'. To extract the namelist and match it against 285 the EIP from the kernel crash, do: 286 287 nm vmlinux | sort | less 288 289 This will give you a list of kernel addresses sorted in ascending 290 order, from which it is simple to find the function that contains the 291 offending address. Note that the address given by the kernel 292 debugging messages will not necessarily match exactly with the 293 function addresses (in fact, that is very unlikely), so you can't 294 just 'grep' the list: the list will, however, give you the starting 295 point of each kernel function, so by looking for the function that 296 has a starting address lower than the one you are searching for but 297 is followed by a function with a higher address you will find the one 298 you want. In fact, it may be a good idea to include a bit of 299 "context" in your problem report, giving a few lines around the 300 interesting one. 301 302 If you for some reason cannot do the above (you have a pre-compiled 303 kernel image or similar), telling me as much about your setup as 304 possible will help. 305 306 - Alternately, you can use gdb on a running kernel. (read-only; i.e. you 307 cannot change values or set break points.) To do this, first compile the 308 kernel with -g; edit arch/i386/Makefile appropriately, then do a "make 309 clean". You'll also need to enable CONFIG_PROC_FS (via "make config"). 310 311 After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore". 312 You can now use all the usual gdb commands. The command to look up the 313 point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes 314 with the EIP value.) 315 316 gdb'ing a non-running kernel currently fails because gdb (wrongly) 317 disregards the starting offset for which the kernel is compiled. 318 319