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 or 58 bzip2 -dc linux-2.6.XX.tar.bz2 | tar xvf - 59 60 61 Replace "XX" with the version number of the latest kernel. 62 63 Do NOT use the /usr/src/linux area! This area has a (usually 64 incomplete) set of kernel headers that are used by the library header 65 files. They should match the library, and not get messed up by 66 whatever the kernel-du-jour happens to be. 67 68 - You can also upgrade between 2.6.xx releases by patching. Patches are 69 distributed in the traditional gzip and the new bzip2 format. To 70 install by patching, get all the newer patch files, enter the 71 top level directory of the kernel source (linux-2.6.xx) and execute: 72 73 gzip -cd ../patch-2.6.xx.gz | patch -p1 74 75 or 76 bzip2 -dc ../patch-2.6.xx.bz2 | patch -p1 77 78 (repeat xx for all versions bigger than the version of your current 79 source tree, _in_order_) and you should be ok. You may want to remove 80 the backup files (xxx~ or xxx.orig), and make sure that there are no 81 failed patches (xxx# or xxx.rej). If there are, either you or me has 82 made a mistake. 83 84 Unlike patches for the 2.6.x kernels, patches for the 2.6.x.y kernels 85 (also known as the -stable kernels) are not incremental but instead apply 86 directly to the base 2.6.x kernel. Please read 87 Documentation/applying-patches.txt for more information. 88 89 Alternatively, the script patch-kernel can be used to automate this 90 process. It determines the current kernel version and applies any 91 patches found. 92 93 linux/scripts/patch-kernel linux 94 95 The first argument in the command above is the location of the 96 kernel source. Patches are applied from the current directory, but 97 an alternative directory can be specified as the second argument. 98 99 - If you are upgrading between releases using the stable series patches 100 (for example, patch-2.6.xx.y), note that these "dot-releases" are 101 not incremental and must be applied to the 2.6.xx base tree. For 102 example, if your base kernel is 2.6.12 and you want to apply the 103 2.6.12.3 patch, you do not and indeed must not first apply the 104 2.6.12.1 and 2.6.12.2 patches. Similarly, if you are running kernel 105 version 2.6.12.2 and want to jump to 2.6.12.3, you must first 106 reverse the 2.6.12.2 patch (that is, patch -R) _before_ applying 107 the 2.6.12.3 patch. 108 109 - Make sure you have no stale .o files and dependencies lying around: 110 111 cd linux 112 make mrproper 113 114 You should now have the sources correctly installed. 115 116SOFTWARE REQUIREMENTS 117 118 Compiling and running the 2.6.xx kernels requires up-to-date 119 versions of various software packages. Consult 120 Documentation/Changes for the minimum version numbers required 121 and how to get updates for these packages. Beware that using 122 excessively old versions of these packages can cause indirect 123 errors that are very difficult to track down, so don't assume that 124 you can just update packages when obvious problems arise during 125 build or operation. 126 127BUILD directory for the kernel: 128 129 When compiling the kernel all output files will per default be 130 stored together with the kernel source code. 131 Using the option "make O=output/dir" allow you to specify an alternate 132 place for the output files (including .config). 133 Example: 134 kernel source code: /usr/src/linux-2.6.N 135 build directory: /home/name/build/kernel 136 137 To configure and build the kernel use: 138 cd /usr/src/linux-2.6.N 139 make O=/home/name/build/kernel menuconfig 140 make O=/home/name/build/kernel 141 sudo make O=/home/name/build/kernel modules_install install 142 143 Please note: If the 'O=output/dir' option is used then it must be 144 used for all invocations of make. 145 146CONFIGURING the kernel: 147 148 Do not skip this step even if you are only upgrading one minor 149 version. New configuration options are added in each release, and 150 odd problems will turn up if the configuration files are not set up 151 as expected. If you want to carry your existing configuration to a 152 new version with minimal work, use "make oldconfig", which will 153 only ask you for the answers to new questions. 154 155 - Alternate configuration commands are: 156 "make menuconfig" Text based color menus, radiolists & dialogs. 157 "make xconfig" X windows (Qt) based configuration tool. 158 "make gconfig" X windows (Gtk) based configuration tool. 159 "make oldconfig" Default all questions based on the contents of 160 your existing ./.config file. 161 "make silentoldconfig" 162 Like above, but avoids cluttering the screen 163 with questions already answered. 164 165 NOTES on "make config": 166 - having unnecessary drivers will make the kernel bigger, and can 167 under some circumstances lead to problems: probing for a 168 nonexistent controller card may confuse your other controllers 169 - compiling the kernel with "Processor type" set higher than 386 170 will result in a kernel that does NOT work on a 386. The 171 kernel will detect this on bootup, and give up. 172 - A kernel with math-emulation compiled in will still use the 173 coprocessor if one is present: the math emulation will just 174 never get used in that case. The kernel will be slightly larger, 175 but will work on different machines regardless of whether they 176 have a math coprocessor or not. 177 - the "kernel hacking" configuration details usually result in a 178 bigger or slower kernel (or both), and can even make the kernel 179 less stable by configuring some routines to actively try to 180 break bad code to find kernel problems (kmalloc()). Thus you 181 should probably answer 'n' to the questions for 182 "development", "experimental", or "debugging" features. 183 184COMPILING the kernel: 185 186 - Make sure you have gcc 2.95.3 available. 187 gcc 2.91.66 (egcs-1.1.2), and gcc 2.7.2.3 are known to miscompile 188 some parts of the kernel, and are *no longer supported*. 189 Also remember to upgrade your binutils package (for as/ld/nm and company) 190 if necessary. For more information, refer to Documentation/Changes. 191 192 Please note that you can still run a.out user programs with this kernel. 193 194 - Do a "make" to create a compressed kernel image. It is also 195 possible to do "make install" if you have lilo installed to suit the 196 kernel makefiles, but you may want to check your particular lilo setup first. 197 198 To do the actual install you have to be root, but none of the normal 199 build should require that. Don't take the name of root in vain. 200 201 - If you configured any of the parts of the kernel as `modules', you 202 will also have to do "make modules_install". 203 204 - Keep a backup kernel handy in case something goes wrong. This is 205 especially true for the development releases, since each new release 206 contains new code which has not been debugged. Make sure you keep a 207 backup of the modules corresponding to that kernel, as well. If you 208 are installing a new kernel with the same version number as your 209 working kernel, make a backup of your modules directory before you 210 do a "make modules_install". 211 Alternatively, before compiling, use the kernel config option 212 "LOCALVERSION" to append a unique suffix to the regular kernel version. 213 LOCALVERSION can be set in the "General Setup" menu. 214 215 - In order to boot your new kernel, you'll need to copy the kernel 216 image (e.g. .../linux/arch/i386/boot/bzImage after compilation) 217 to the place where your regular bootable kernel is found. 218 219 - Booting a kernel directly from a floppy without the assistance of a 220 bootloader such as LILO, is no longer supported. 221 222 If you boot Linux from the hard drive, chances are you use LILO which 223 uses the kernel image as specified in the file /etc/lilo.conf. The 224 kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or 225 /boot/bzImage. To use the new kernel, save a copy of the old image 226 and copy the new image over the old one. Then, you MUST RERUN LILO 227 to update the loading map!! If you don't, you won't be able to boot 228 the new kernel image. 229 230 Reinstalling LILO is usually a matter of running /sbin/lilo. 231 You may wish to edit /etc/lilo.conf to specify an entry for your 232 old kernel image (say, /vmlinux.old) in case the new one does not 233 work. See the LILO docs for more information. 234 235 After reinstalling LILO, you should be all set. Shutdown the system, 236 reboot, and enjoy! 237 238 If you ever need to change the default root device, video mode, 239 ramdisk size, etc. in the kernel image, use the 'rdev' program (or 240 alternatively the LILO boot options when appropriate). No need to 241 recompile the kernel to change these parameters. 242 243 - Reboot with the new kernel and enjoy. 244 245IF SOMETHING GOES WRONG: 246 247 - If you have problems that seem to be due to kernel bugs, please check 248 the file MAINTAINERS to see if there is a particular person associated 249 with the part of the kernel that you are having trouble with. If there 250 isn't anyone listed there, then the second best thing is to mail 251 them to me (torvalds@osdl.org), and possibly to any other relevant 252 mailing-list or to the newsgroup. 253 254 - In all bug-reports, *please* tell what kernel you are talking about, 255 how to duplicate the problem, and what your setup is (use your common 256 sense). If the problem is new, tell me so, and if the problem is 257 old, please try to tell me when you first noticed it. 258 259 - If the bug results in a message like 260 261 unable to handle kernel paging request at address C0000010 262 Oops: 0002 263 EIP: 0010:XXXXXXXX 264 eax: xxxxxxxx ebx: xxxxxxxx ecx: xxxxxxxx edx: xxxxxxxx 265 esi: xxxxxxxx edi: xxxxxxxx ebp: xxxxxxxx 266 ds: xxxx es: xxxx fs: xxxx gs: xxxx 267 Pid: xx, process nr: xx 268 xx xx xx xx xx xx xx xx xx xx 269 270 or similar kernel debugging information on your screen or in your 271 system log, please duplicate it *exactly*. The dump may look 272 incomprehensible to you, but it does contain information that may 273 help debugging the problem. The text above the dump is also 274 important: it tells something about why the kernel dumped code (in 275 the above example it's due to a bad kernel pointer). More information 276 on making sense of the dump is in Documentation/oops-tracing.txt 277 278 - If you compiled the kernel with CONFIG_KALLSYMS you can send the dump 279 as is, otherwise you will have to use the "ksymoops" program to make 280 sense of the dump. This utility can be downloaded from 281 ftp://ftp.<country>.kernel.org/pub/linux/utils/kernel/ksymoops. 282 Alternately you can do the dump lookup by hand: 283 284 - In debugging dumps like the above, it helps enormously if you can 285 look up what the EIP value means. The hex value as such doesn't help 286 me or anybody else very much: it will depend on your particular 287 kernel setup. What you should do is take the hex value from the EIP 288 line (ignore the "0010:"), and look it up in the kernel namelist to 289 see which kernel function contains the offending address. 290 291 To find out the kernel function name, you'll need to find the system 292 binary associated with the kernel that exhibited the symptom. This is 293 the file 'linux/vmlinux'. To extract the namelist and match it against 294 the EIP from the kernel crash, do: 295 296 nm vmlinux | sort | less 297 298 This will give you a list of kernel addresses sorted in ascending 299 order, from which it is simple to find the function that contains the 300 offending address. Note that the address given by the kernel 301 debugging messages will not necessarily match exactly with the 302 function addresses (in fact, that is very unlikely), so you can't 303 just 'grep' the list: the list will, however, give you the starting 304 point of each kernel function, so by looking for the function that 305 has a starting address lower than the one you are searching for but 306 is followed by a function with a higher address you will find the one 307 you want. In fact, it may be a good idea to include a bit of 308 "context" in your problem report, giving a few lines around the 309 interesting one. 310 311 If you for some reason cannot do the above (you have a pre-compiled 312 kernel image or similar), telling me as much about your setup as 313 possible will help. 314 315 - Alternately, you can use gdb on a running kernel. (read-only; i.e. you 316 cannot change values or set break points.) To do this, first compile the 317 kernel with -g; edit arch/i386/Makefile appropriately, then do a "make 318 clean". You'll also need to enable CONFIG_PROC_FS (via "make config"). 319 320 After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore". 321 You can now use all the usual gdb commands. The command to look up the 322 point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes 323 with the EIP value.) 324 325 gdb'ing a non-running kernel currently fails because gdb (wrongly) 326 disregards the starting offset for which the kernel is compiled. 327 328