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, 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, and HTML, among others. 56 After installation, "make psdocs", "make pdfdocs", or "make htmldocs" 57 will render the documentation in the requested format. 58 59INSTALLING the kernel: 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 xconfig" X windows (Qt) based configuration tool. 170 "make gconfig" X windows (Gtk) based configuration tool. 171 "make oldconfig" Default all questions based on the contents of 172 your existing ./.config file and asking about 173 new config symbols. 174 "make silentoldconfig" 175 Like above, but avoids cluttering the screen 176 with questions already answered. 177 "make defconfig" Create a ./.config file by using the default 178 symbol values from arch/$ARCH/defconfig. 179 "make allyesconfig" 180 Create a ./.config file by setting symbol 181 values to 'y' as much as possible. 182 "make allmodconfig" 183 Create a ./.config file by setting symbol 184 values to 'm' as much as possible. 185 "make allnoconfig" Create a ./.config file by setting symbol 186 values to 'n' as much as possible. 187 "make randconfig" Create a ./.config file by setting symbol 188 values to random values. 189 190 The allyesconfig/allmodconfig/allnoconfig/randconfig variants can 191 also use the environment variable KCONFIG_ALLCONFIG to specify a 192 filename that contains config options that the user requires to be 193 set to a specific value. If KCONFIG_ALLCONFIG=filename is not used, 194 "make *config" checks for a file named "all{yes/mod/no/random}.config" 195 for symbol values that are to be forced. If this file is not found, 196 it checks for a file named "all.config" to contain forced values. 197 198 NOTES on "make config": 199 - having unnecessary drivers will make the kernel bigger, and can 200 under some circumstances lead to problems: probing for a 201 nonexistent controller card may confuse your other controllers 202 - compiling the kernel with "Processor type" set higher than 386 203 will result in a kernel that does NOT work on a 386. The 204 kernel will detect this on bootup, and give up. 205 - A kernel with math-emulation compiled in will still use the 206 coprocessor if one is present: the math emulation will just 207 never get used in that case. The kernel will be slightly larger, 208 but will work on different machines regardless of whether they 209 have a math coprocessor or not. 210 - the "kernel hacking" configuration details usually result in a 211 bigger or slower kernel (or both), and can even make the kernel 212 less stable by configuring some routines to actively try to 213 break bad code to find kernel problems (kmalloc()). Thus you 214 should probably answer 'n' to the questions for 215 "development", "experimental", or "debugging" features. 216 217COMPILING the kernel: 218 219 - Make sure you have at least gcc 3.2 available. 220 For more information, refer to Documentation/Changes. 221 222 Please note that you can still run a.out user programs with this kernel. 223 224 - Do a "make" to create a compressed kernel image. It is also 225 possible to do "make install" if you have lilo installed to suit the 226 kernel makefiles, but you may want to check your particular lilo setup first. 227 228 To do the actual install you have to be root, but none of the normal 229 build should require that. Don't take the name of root in vain. 230 231 - If you configured any of the parts of the kernel as `modules', you 232 will also have to do "make modules_install". 233 234 - Keep a backup kernel handy in case something goes wrong. This is 235 especially true for the development releases, since each new release 236 contains new code which has not been debugged. Make sure you keep a 237 backup of the modules corresponding to that kernel, as well. If you 238 are installing a new kernel with the same version number as your 239 working kernel, make a backup of your modules directory before you 240 do a "make modules_install". 241 Alternatively, before compiling, use the kernel config option 242 "LOCALVERSION" to append a unique suffix to the regular kernel version. 243 LOCALVERSION can be set in the "General Setup" menu. 244 245 - In order to boot your new kernel, you'll need to copy the kernel 246 image (e.g. .../linux/arch/i386/boot/bzImage after compilation) 247 to the place where your regular bootable kernel is found. 248 249 - Booting a kernel directly from a floppy without the assistance of a 250 bootloader such as LILO, is no longer supported. 251 252 If you boot Linux from the hard drive, chances are you use LILO which 253 uses the kernel image as specified in the file /etc/lilo.conf. The 254 kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or 255 /boot/bzImage. To use the new kernel, save a copy of the old image 256 and copy the new image over the old one. Then, you MUST RERUN LILO 257 to update the loading map!! If you don't, you won't be able to boot 258 the new kernel image. 259 260 Reinstalling LILO is usually a matter of running /sbin/lilo. 261 You may wish to edit /etc/lilo.conf to specify an entry for your 262 old kernel image (say, /vmlinux.old) in case the new one does not 263 work. See the LILO docs for more information. 264 265 After reinstalling LILO, you should be all set. Shutdown the system, 266 reboot, and enjoy! 267 268 If you ever need to change the default root device, video mode, 269 ramdisk size, etc. in the kernel image, use the 'rdev' program (or 270 alternatively the LILO boot options when appropriate). No need to 271 recompile the kernel to change these parameters. 272 273 - Reboot with the new kernel and enjoy. 274 275IF SOMETHING GOES WRONG: 276 277 - If you have problems that seem to be due to kernel bugs, please check 278 the file MAINTAINERS to see if there is a particular person associated 279 with the part of the kernel that you are having trouble with. If there 280 isn't anyone listed there, then the second best thing is to mail 281 them to me (torvalds@linux-foundation.org), and possibly to any other 282 relevant mailing-list or to the newsgroup. 283 284 - In all bug-reports, *please* tell what kernel you are talking about, 285 how to duplicate the problem, and what your setup is (use your common 286 sense). If the problem is new, tell me so, and if the problem is 287 old, please try to tell me when you first noticed it. 288 289 - If the bug results in a message like 290 291 unable to handle kernel paging request at address C0000010 292 Oops: 0002 293 EIP: 0010:XXXXXXXX 294 eax: xxxxxxxx ebx: xxxxxxxx ecx: xxxxxxxx edx: xxxxxxxx 295 esi: xxxxxxxx edi: xxxxxxxx ebp: xxxxxxxx 296 ds: xxxx es: xxxx fs: xxxx gs: xxxx 297 Pid: xx, process nr: xx 298 xx xx xx xx xx xx xx xx xx xx 299 300 or similar kernel debugging information on your screen or in your 301 system log, please duplicate it *exactly*. The dump may look 302 incomprehensible to you, but it does contain information that may 303 help debugging the problem. The text above the dump is also 304 important: it tells something about why the kernel dumped code (in 305 the above example it's due to a bad kernel pointer). More information 306 on making sense of the dump is in Documentation/oops-tracing.txt 307 308 - If you compiled the kernel with CONFIG_KALLSYMS you can send the dump 309 as is, otherwise you will have to use the "ksymoops" program to make 310 sense of the dump (but compiling with CONFIG_KALLSYMS is usually preferred). 311 This utility can be downloaded from 312 ftp://ftp.<country>.kernel.org/pub/linux/utils/kernel/ksymoops/ . 313 Alternately you can do the dump lookup by hand: 314 315 - In debugging dumps like the above, it helps enormously if you can 316 look up what the EIP value means. The hex value as such doesn't help 317 me or anybody else very much: it will depend on your particular 318 kernel setup. What you should do is take the hex value from the EIP 319 line (ignore the "0010:"), and look it up in the kernel namelist to 320 see which kernel function contains the offending address. 321 322 To find out the kernel function name, you'll need to find the system 323 binary associated with the kernel that exhibited the symptom. This is 324 the file 'linux/vmlinux'. To extract the namelist and match it against 325 the EIP from the kernel crash, do: 326 327 nm vmlinux | sort | less 328 329 This will give you a list of kernel addresses sorted in ascending 330 order, from which it is simple to find the function that contains the 331 offending address. Note that the address given by the kernel 332 debugging messages will not necessarily match exactly with the 333 function addresses (in fact, that is very unlikely), so you can't 334 just 'grep' the list: the list will, however, give you the starting 335 point of each kernel function, so by looking for the function that 336 has a starting address lower than the one you are searching for but 337 is followed by a function with a higher address you will find the one 338 you want. In fact, it may be a good idea to include a bit of 339 "context" in your problem report, giving a few lines around the 340 interesting one. 341 342 If you for some reason cannot do the above (you have a pre-compiled 343 kernel image or similar), telling me as much about your setup as 344 possible will help. Please read the REPORTING-BUGS document for details. 345 346 - Alternately, you can use gdb on a running kernel. (read-only; i.e. you 347 cannot change values or set break points.) To do this, first compile the 348 kernel with -g; edit arch/i386/Makefile appropriately, then do a "make 349 clean". You'll also need to enable CONFIG_PROC_FS (via "make config"). 350 351 After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore". 352 You can now use all the usual gdb commands. The command to look up the 353 point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes 354 with the EIP value.) 355 356 gdb'ing a non-running kernel currently fails because gdb (wrongly) 357 disregards the starting offset for which the kernel is compiled. 358 359