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1 | .. _readme: |
2 | ||
0358affb | 3 | Linux kernel release 5.x <http://kernel.org/> |
44b10006 | 4 | ============================================= |
1da177e4 | 5 | |
0358affb | 6 | These are the release notes for Linux version 5. Read them carefully, |
1da177e4 | 7 | as they tell you what this is all about, explain how to install the |
cfaf790f | 8 | kernel, and what to do if something goes wrong. |
1da177e4 | 9 | |
44b10006 MCC |
10 | What is Linux? |
11 | -------------- | |
1da177e4 | 12 | |
4f4e2dc3 XVP |
13 | Linux is a clone of the operating system Unix, written from scratch by |
14 | Linus Torvalds with assistance from a loosely-knit team of hackers across | |
15 | the Net. It aims towards POSIX and Single UNIX Specification compliance. | |
1da177e4 | 16 | |
4f4e2dc3 XVP |
17 | It has all the features you would expect in a modern fully-fledged Unix, |
18 | including true multitasking, virtual memory, shared libraries, demand | |
19 | loading, shared copy-on-write executables, proper memory management, | |
20 | and multistack networking including IPv4 and IPv6. | |
1da177e4 | 21 | |
e57ae44a | 22 | It is distributed under the GNU General Public License v2 - see the |
cfaf790f | 23 | accompanying COPYING file for more details. |
1da177e4 | 24 | |
44b10006 MCC |
25 | On what hardware does it run? |
26 | ----------------------------- | |
1da177e4 | 27 | |
4f4e2dc3 XVP |
28 | Although originally developed first for 32-bit x86-based PCs (386 or higher), |
29 | today Linux also runs on (at least) the Compaq Alpha AXP, Sun SPARC and | |
620034c8 | 30 | UltraSPARC, Motorola 68000, PowerPC, PowerPC64, ARM, Hitachi SuperH, Cell, |
1ea5afd4 AB |
31 | IBM S/390, MIPS, HP PA-RISC, Intel IA-64, DEC VAX, AMD x86-64 Xtensa, and |
32 | ARC architectures. | |
4f4e2dc3 XVP |
33 | |
34 | Linux is easily portable to most general-purpose 32- or 64-bit architectures | |
35 | as long as they have a paged memory management unit (PMMU) and a port of the | |
36 | GNU C compiler (gcc) (part of The GNU Compiler Collection, GCC). Linux has | |
37 | also been ported to a number of architectures without a PMMU, although | |
38 | functionality is then obviously somewhat limited. | |
620034c8 JJ |
39 | Linux has also been ported to itself. You can now run the kernel as a |
40 | userspace application - this is called UserMode Linux (UML). | |
1da177e4 | 41 | |
44b10006 MCC |
42 | Documentation |
43 | ------------- | |
1da177e4 LT |
44 | |
45 | - There is a lot of documentation available both in electronic form on | |
46 | the Internet and in books, both Linux-specific and pertaining to | |
47 | general UNIX questions. I'd recommend looking into the documentation | |
48 | subdirectories on any Linux FTP site for the LDP (Linux Documentation | |
49 | Project) books. This README is not meant to be documentation on the | |
50 | system: there are much better sources available. | |
51 | ||
52 | - There are various README files in the Documentation/ subdirectory: | |
cfaf790f | 53 | these typically contain kernel-specific installation notes for some |
a7ddcea5 | 54 | drivers for example. Please read the |
8c27ceff | 55 | :ref:`Documentation/process/changes.rst <changes>` file, as it |
1da177e4 LT |
56 | contains information about the problems, which may result by upgrading |
57 | your kernel. | |
58 | ||
44b10006 MCC |
59 | Installing the kernel source |
60 | ---------------------------- | |
1da177e4 LT |
61 | |
62 | - If you install the full sources, put the kernel tarball in a | |
3047bcc5 | 63 | directory where you have permissions (e.g. your home directory) and |
44b10006 | 64 | unpack it:: |
1da177e4 | 65 | |
0358affb | 66 | xz -cd linux-5.x.tar.xz | tar xvf - |
b39f72fe | 67 | |
5b4285fb | 68 | Replace "X" with the version number of the latest kernel. |
1da177e4 LT |
69 | |
70 | Do NOT use the /usr/src/linux area! This area has a (usually | |
71 | incomplete) set of kernel headers that are used by the library header | |
72 | files. They should match the library, and not get messed up by | |
73 | whatever the kernel-du-jour happens to be. | |
74 | ||
0358affb | 75 | - You can also upgrade between 5.x releases by patching. Patches are |
1913c6f4 YB |
76 | distributed in the xz format. To install by patching, get all the |
77 | newer patch files, enter the top level directory of the kernel source | |
0358affb | 78 | (linux-5.x) and execute:: |
88f7a642 | 79 | |
0358affb | 80 | xz -cd ../patch-5.x.xz | patch -p1 |
1da177e4 | 81 | |
0358affb | 82 | Replace "x" for all versions bigger than the version "x" of your current |
44b10006 | 83 | source tree, **in_order**, and you should be ok. You may want to remove |
5b4285fb MW |
84 | the backup files (some-file-name~ or some-file-name.orig), and make sure |
85 | that there are no failed patches (some-file-name# or some-file-name.rej). | |
a20e3a79 | 86 | If there are, either you or I have made a mistake. |
1da177e4 | 87 | |
0358affb | 88 | Unlike patches for the 5.x kernels, patches for the 5.x.y kernels |
6ad44229 | 89 | (also known as the -stable kernels) are not incremental but instead apply |
0358affb AB |
90 | directly to the base 5.x kernel. For example, if your base kernel is 5.0 |
91 | and you want to apply the 5.0.3 patch, you must not first apply the 5.0.1 | |
92 | and 5.0.2 patches. Similarly, if you are running kernel version 5.0.2 and | |
93 | want to jump to 5.0.3, you must first reverse the 5.0.2 patch (that is, | |
94 | patch -R) **before** applying the 5.0.3 patch. You can read more on this in | |
8c27ceff | 95 | :ref:`Documentation/process/applying-patches.rst <applying_patches>`. |
6ad44229 | 96 | |
1da177e4 LT |
97 | Alternatively, the script patch-kernel can be used to automate this |
98 | process. It determines the current kernel version and applies any | |
44b10006 | 99 | patches found:: |
1da177e4 | 100 | |
3773b454 | 101 | linux/scripts/patch-kernel linux |
1da177e4 LT |
102 | |
103 | The first argument in the command above is the location of the | |
104 | kernel source. Patches are applied from the current directory, but | |
105 | an alternative directory can be specified as the second argument. | |
106 | ||
44b10006 | 107 | - Make sure you have no stale .o files and dependencies lying around:: |
1da177e4 | 108 | |
3773b454 MW |
109 | cd linux |
110 | make mrproper | |
1da177e4 LT |
111 | |
112 | You should now have the sources correctly installed. | |
113 | ||
44b10006 MCC |
114 | Software requirements |
115 | --------------------- | |
1da177e4 | 116 | |
0358affb | 117 | Compiling and running the 5.x kernels requires up-to-date |
1da177e4 | 118 | versions of various software packages. Consult |
8c27ceff | 119 | :ref:`Documentation/process/changes.rst <changes>` for the minimum version numbers |
44b10006 | 120 | required and how to get updates for these packages. Beware that using |
1da177e4 LT |
121 | excessively old versions of these packages can cause indirect |
122 | errors that are very difficult to track down, so don't assume that | |
123 | you can just update packages when obvious problems arise during | |
124 | build or operation. | |
125 | ||
44b10006 MCC |
126 | Build directory for the kernel |
127 | ------------------------------ | |
1da177e4 | 128 | |
a6144bb9 | 129 | When compiling the kernel, all output files will per default be |
1da177e4 | 130 | stored together with the kernel source code. |
44b10006 | 131 | Using the option ``make O=output/dir`` allows you to specify an alternate |
1da177e4 | 132 | place for the output files (including .config). |
44b10006 | 133 | Example:: |
88f7a642 | 134 | |
0358affb | 135 | kernel source code: /usr/src/linux-5.x |
3773b454 | 136 | build directory: /home/name/build/kernel |
1da177e4 | 137 | |
44b10006 | 138 | To configure and build the kernel, use:: |
88f7a642 | 139 | |
0358affb | 140 | cd /usr/src/linux-5.x |
88f7a642 MW |
141 | make O=/home/name/build/kernel menuconfig |
142 | make O=/home/name/build/kernel | |
143 | sudo make O=/home/name/build/kernel modules_install install | |
1da177e4 | 144 | |
44b10006 | 145 | Please note: If the ``O=output/dir`` option is used, then it must be |
1da177e4 LT |
146 | used for all invocations of make. |
147 | ||
44b10006 MCC |
148 | Configuring the kernel |
149 | ---------------------- | |
1da177e4 LT |
150 | |
151 | Do not skip this step even if you are only upgrading one minor | |
152 | version. New configuration options are added in each release, and | |
153 | odd problems will turn up if the configuration files are not set up | |
154 | as expected. If you want to carry your existing configuration to a | |
44b10006 | 155 | new version with minimal work, use ``make oldconfig``, which will |
1da177e4 LT |
156 | only ask you for the answers to new questions. |
157 | ||
44b10006 | 158 | - Alternative configuration commands are:: |
88f7a642 | 159 | |
3773b454 | 160 | "make config" Plain text interface. |
88f7a642 | 161 | |
3773b454 | 162 | "make menuconfig" Text based color menus, radiolists & dialogs. |
88f7a642 | 163 | |
3773b454 | 164 | "make nconfig" Enhanced text based color menus. |
88f7a642 | 165 | |
3047bcc5 | 166 | "make xconfig" Qt based configuration tool. |
88f7a642 | 167 | |
3047bcc5 | 168 | "make gconfig" GTK+ based configuration tool. |
88f7a642 | 169 | |
3773b454 MW |
170 | "make oldconfig" Default all questions based on the contents of |
171 | your existing ./.config file and asking about | |
172 | new config symbols. | |
88f7a642 | 173 | |
fc0d1b93 KC |
174 | "make olddefconfig" |
175 | Like above, but sets new symbols to their default | |
176 | values without prompting. | |
177 | ||
3773b454 MW |
178 | "make defconfig" Create a ./.config file by using the default |
179 | symbol values from either arch/$ARCH/defconfig | |
180 | or arch/$ARCH/configs/${PLATFORM}_defconfig, | |
181 | depending on the architecture. | |
88f7a642 | 182 | |
3773b454 MW |
183 | "make ${PLATFORM}_defconfig" |
184 | Create a ./.config file by using the default | |
185 | symbol values from | |
186 | arch/$ARCH/configs/${PLATFORM}_defconfig. | |
187 | Use "make help" to get a list of all available | |
188 | platforms of your architecture. | |
88f7a642 | 189 | |
3773b454 MW |
190 | "make allyesconfig" |
191 | Create a ./.config file by setting symbol | |
192 | values to 'y' as much as possible. | |
88f7a642 | 193 | |
3773b454 MW |
194 | "make allmodconfig" |
195 | Create a ./.config file by setting symbol | |
196 | values to 'm' as much as possible. | |
88f7a642 | 197 | |
3773b454 MW |
198 | "make allnoconfig" Create a ./.config file by setting symbol |
199 | values to 'n' as much as possible. | |
88f7a642 | 200 | |
3773b454 MW |
201 | "make randconfig" Create a ./.config file by setting symbol |
202 | values to random values. | |
9dfb563b | 203 | |
80b810b2 SR |
204 | "make localmodconfig" Create a config based on current config and |
205 | loaded modules (lsmod). Disables any module | |
206 | option that is not needed for the loaded modules. | |
207 | ||
208 | To create a localmodconfig for another machine, | |
209 | store the lsmod of that machine into a file | |
210 | and pass it in as a LSMOD parameter. | |
211 | ||
c027b02d CD |
212 | Also, you can preserve modules in certain folders |
213 | or kconfig files by specifying their paths in | |
214 | parameter LMC_KEEP. | |
215 | ||
80b810b2 SR |
216 | target$ lsmod > /tmp/mylsmod |
217 | target$ scp /tmp/mylsmod host:/tmp | |
218 | ||
c027b02d CD |
219 | host$ make LSMOD=/tmp/mylsmod \ |
220 | LMC_KEEP="drivers/usb:drivers/gpu:fs" \ | |
221 | localmodconfig | |
80b810b2 SR |
222 | |
223 | The above also works when cross compiling. | |
224 | ||
225 | "make localyesconfig" Similar to localmodconfig, except it will convert | |
c027b02d CD |
226 | all module options to built in (=y) options. You can |
227 | also preserve modules by LMC_KEEP. | |
80b810b2 | 228 | |
52c37d41 MK |
229 | "make kvmconfig" Enable additional options for kvm guest kernel support. |
230 | ||
231 | "make xenconfig" Enable additional options for xen dom0 guest kernel | |
232 | support. | |
233 | ||
234 | "make tinyconfig" Configure the tiniest possible kernel. | |
235 | ||
2af238e4 | 236 | You can find more information on using the Linux kernel config tools |
cd238eff | 237 | in Documentation/kbuild/kconfig.rst. |
2af238e4 | 238 | |
44b10006 | 239 | - NOTES on ``make config``: |
88f7a642 | 240 | |
3773b454 MW |
241 | - Having unnecessary drivers will make the kernel bigger, and can |
242 | under some circumstances lead to problems: probing for a | |
e57ae44a | 243 | nonexistent controller card may confuse your other controllers. |
88f7a642 | 244 | |
3773b454 MW |
245 | - A kernel with math-emulation compiled in will still use the |
246 | coprocessor if one is present: the math emulation will just | |
247 | never get used in that case. The kernel will be slightly larger, | |
248 | but will work on different machines regardless of whether they | |
249 | have a math coprocessor or not. | |
88f7a642 | 250 | |
3773b454 MW |
251 | - The "kernel hacking" configuration details usually result in a |
252 | bigger or slower kernel (or both), and can even make the kernel | |
253 | less stable by configuring some routines to actively try to | |
254 | break bad code to find kernel problems (kmalloc()). Thus you | |
255 | should probably answer 'n' to the questions for "development", | |
256 | "experimental", or "debugging" features. | |
1da177e4 | 257 | |
44b10006 MCC |
258 | Compiling the kernel |
259 | -------------------- | |
1da177e4 | 260 | |
0bddd227 | 261 | - Make sure you have at least gcc 4.9 available. |
8c27ceff | 262 | For more information, refer to :ref:`Documentation/process/changes.rst <changes>`. |
1da177e4 LT |
263 | |
264 | Please note that you can still run a.out user programs with this kernel. | |
265 | ||
44b10006 MCC |
266 | - Do a ``make`` to create a compressed kernel image. It is also |
267 | possible to do ``make install`` if you have lilo installed to suit the | |
1da177e4 LT |
268 | kernel makefiles, but you may want to check your particular lilo setup first. |
269 | ||
a6144bb9 | 270 | To do the actual install, you have to be root, but none of the normal |
1da177e4 LT |
271 | build should require that. Don't take the name of root in vain. |
272 | ||
44b10006 MCC |
273 | - If you configured any of the parts of the kernel as ``modules``, you |
274 | will also have to do ``make modules_install``. | |
1da177e4 | 275 | |
2af238e4 RD |
276 | - Verbose kernel compile/build output: |
277 | ||
a6144bb9 | 278 | Normally, the kernel build system runs in a fairly quiet mode (but not |
2af238e4 RD |
279 | totally silent). However, sometimes you or other kernel developers need |
280 | to see compile, link, or other commands exactly as they are executed. | |
3047bcc5 | 281 | For this, use "verbose" build mode. This is done by passing |
44b10006 | 282 | ``V=1`` to the ``make`` command, e.g.:: |
2af238e4 | 283 | |
3773b454 | 284 | make V=1 all |
2af238e4 RD |
285 | |
286 | To have the build system also tell the reason for the rebuild of each | |
44b10006 | 287 | target, use ``V=2``. The default is ``V=0``. |
2af238e4 | 288 | |
cfaf790f | 289 | - Keep a backup kernel handy in case something goes wrong. This is |
1da177e4 LT |
290 | especially true for the development releases, since each new release |
291 | contains new code which has not been debugged. Make sure you keep a | |
292 | backup of the modules corresponding to that kernel, as well. If you | |
293 | are installing a new kernel with the same version number as your | |
294 | working kernel, make a backup of your modules directory before you | |
44b10006 | 295 | do a ``make modules_install``. |
88f7a642 | 296 | |
e3fc4cc1 RD |
297 | Alternatively, before compiling, use the kernel config option |
298 | "LOCALVERSION" to append a unique suffix to the regular kernel version. | |
299 | LOCALVERSION can be set in the "General Setup" menu. | |
1da177e4 LT |
300 | |
301 | - In order to boot your new kernel, you'll need to copy the kernel | |
35db7e94 | 302 | image (e.g. .../linux/arch/x86/boot/bzImage after compilation) |
cfaf790f | 303 | to the place where your regular bootable kernel is found. |
1da177e4 LT |
304 | |
305 | - Booting a kernel directly from a floppy without the assistance of a | |
306 | bootloader such as LILO, is no longer supported. | |
307 | ||
a6144bb9 | 308 | If you boot Linux from the hard drive, chances are you use LILO, which |
1da177e4 LT |
309 | uses the kernel image as specified in the file /etc/lilo.conf. The |
310 | kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or | |
311 | /boot/bzImage. To use the new kernel, save a copy of the old image | |
312 | and copy the new image over the old one. Then, you MUST RERUN LILO | |
3047bcc5 | 313 | to update the loading map! If you don't, you won't be able to boot |
1da177e4 LT |
314 | the new kernel image. |
315 | ||
cfaf790f | 316 | Reinstalling LILO is usually a matter of running /sbin/lilo. |
1da177e4 LT |
317 | You may wish to edit /etc/lilo.conf to specify an entry for your |
318 | old kernel image (say, /vmlinux.old) in case the new one does not | |
cfaf790f | 319 | work. See the LILO docs for more information. |
1da177e4 LT |
320 | |
321 | After reinstalling LILO, you should be all set. Shutdown the system, | |
322 | reboot, and enjoy! | |
323 | ||
324 | If you ever need to change the default root device, video mode, | |
fc67d5bc RD |
325 | etc. in the kernel image, use your bootloader's boot options |
326 | where appropriate. No need to recompile the kernel to change | |
327 | these parameters. | |
1da177e4 | 328 | |
cfaf790f | 329 | - Reboot with the new kernel and enjoy. |
1da177e4 | 330 | |
44b10006 MCC |
331 | If something goes wrong |
332 | ----------------------- | |
1da177e4 LT |
333 | |
334 | - If you have problems that seem to be due to kernel bugs, please check | |
335 | the file MAINTAINERS to see if there is a particular person associated | |
336 | with the part of the kernel that you are having trouble with. If there | |
337 | isn't anyone listed there, then the second best thing is to mail | |
99ddcc7e LT |
338 | them to me (torvalds@linux-foundation.org), and possibly to any other |
339 | relevant mailing-list or to the newsgroup. | |
1da177e4 LT |
340 | |
341 | - In all bug-reports, *please* tell what kernel you are talking about, | |
342 | how to duplicate the problem, and what your setup is (use your common | |
343 | sense). If the problem is new, tell me so, and if the problem is | |
344 | old, please try to tell me when you first noticed it. | |
345 | ||
44b10006 | 346 | - If the bug results in a message like:: |
1da177e4 | 347 | |
3773b454 MW |
348 | unable to handle kernel paging request at address C0000010 |
349 | Oops: 0002 | |
350 | EIP: 0010:XXXXXXXX | |
351 | eax: xxxxxxxx ebx: xxxxxxxx ecx: xxxxxxxx edx: xxxxxxxx | |
352 | esi: xxxxxxxx edi: xxxxxxxx ebp: xxxxxxxx | |
353 | ds: xxxx es: xxxx fs: xxxx gs: xxxx | |
354 | Pid: xx, process nr: xx | |
355 | xx xx xx xx xx xx xx xx xx xx | |
1da177e4 LT |
356 | |
357 | or similar kernel debugging information on your screen or in your | |
358 | system log, please duplicate it *exactly*. The dump may look | |
359 | incomprehensible to you, but it does contain information that may | |
360 | help debugging the problem. The text above the dump is also | |
361 | important: it tells something about why the kernel dumped code (in | |
a6144bb9 | 362 | the above example, it's due to a bad kernel pointer). More information |
3ba9b1b8 | 363 | on making sense of the dump is in Documentation/admin-guide/bug-hunting.rst |
1da177e4 LT |
364 | |
365 | - If you compiled the kernel with CONFIG_KALLSYMS you can send the dump | |
44b10006 | 366 | as is, otherwise you will have to use the ``ksymoops`` program to make |
620034c8 JJ |
367 | sense of the dump (but compiling with CONFIG_KALLSYMS is usually preferred). |
368 | This utility can be downloaded from | |
25a0da73 | 369 | https://www.kernel.org/pub/linux/utils/kernel/ksymoops/ . |
6d12760c | 370 | Alternatively, you can do the dump lookup by hand: |
1da177e4 LT |
371 | |
372 | - In debugging dumps like the above, it helps enormously if you can | |
373 | look up what the EIP value means. The hex value as such doesn't help | |
374 | me or anybody else very much: it will depend on your particular | |
375 | kernel setup. What you should do is take the hex value from the EIP | |
44b10006 | 376 | line (ignore the ``0010:``), and look it up in the kernel namelist to |
1da177e4 LT |
377 | see which kernel function contains the offending address. |
378 | ||
379 | To find out the kernel function name, you'll need to find the system | |
380 | binary associated with the kernel that exhibited the symptom. This is | |
381 | the file 'linux/vmlinux'. To extract the namelist and match it against | |
44b10006 | 382 | the EIP from the kernel crash, do:: |
1da177e4 | 383 | |
3773b454 | 384 | nm vmlinux | sort | less |
1da177e4 LT |
385 | |
386 | This will give you a list of kernel addresses sorted in ascending | |
387 | order, from which it is simple to find the function that contains the | |
388 | offending address. Note that the address given by the kernel | |
389 | debugging messages will not necessarily match exactly with the | |
390 | function addresses (in fact, that is very unlikely), so you can't | |
391 | just 'grep' the list: the list will, however, give you the starting | |
392 | point of each kernel function, so by looking for the function that | |
393 | has a starting address lower than the one you are searching for but | |
394 | is followed by a function with a higher address you will find the one | |
395 | you want. In fact, it may be a good idea to include a bit of | |
396 | "context" in your problem report, giving a few lines around the | |
cfaf790f | 397 | interesting one. |
1da177e4 LT |
398 | |
399 | If you for some reason cannot do the above (you have a pre-compiled | |
400 | kernel image or similar), telling me as much about your setup as | |
8c27ceff | 401 | possible will help. Please read the :ref:`admin-guide/reporting-bugs.rst <reportingbugs>` |
44b10006 | 402 | document for details. |
1da177e4 | 403 | |
6d12760c | 404 | - Alternatively, you can use gdb on a running kernel. (read-only; i.e. you |
1da177e4 | 405 | cannot change values or set break points.) To do this, first compile the |
44b10006 MCC |
406 | kernel with -g; edit arch/x86/Makefile appropriately, then do a ``make |
407 | clean``. You'll also need to enable CONFIG_PROC_FS (via ``make config``). | |
1da177e4 | 408 | |
44b10006 | 409 | After you've rebooted with the new kernel, do ``gdb vmlinux /proc/kcore``. |
1da177e4 | 410 | You can now use all the usual gdb commands. The command to look up the |
44b10006 | 411 | point where your system crashed is ``l *0xXXXXXXXX``. (Replace the XXXes |
1da177e4 LT |
412 | with the EIP value.) |
413 | ||
44b10006 | 414 | gdb'ing a non-running kernel currently fails because ``gdb`` (wrongly) |
1da177e4 | 415 | disregards the starting offset for which the kernel is compiled. |