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1 swift 1.1 <?xml version="1.0" encoding="UTF-8"?>
2 neysx 1.8 <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/kernel-upgrade.xml,v 1.7 2005/05/25 17:17:27 swift Exp $ -->
3 swift 1.1
4     <!DOCTYPE guide SYSTEM "/dtd/guide.dtd">
5 neysx 1.3 <guide link="/doc/en/kernel-upgrade.xml">
6 swift 1.1 <title>Gentoo Linux Kernel Upgrade Guide</title>
7     <author title="Author">
8     <mail link="dsd@gentoo.org">Daniel Drake</mail>
9     </author>
10    
11     <abstract>
12     This document describes the process of upgrading your kernel from one release
13     to another.
14     </abstract>
15    
16     <!-- The content of this document is licensed under the CC-BY-SA license -->
17     <!-- See http://creativecommons.org/licenses/by-sa/2.0 -->
18     <license/>
19    
20 neysx 1.8 <version>0.1.6</version>
21     <date>2005-06-04</date>
22 swift 1.1
23     <chapter>
24     <title>Introduction</title>
25     <section>
26     <body>
27    
28     <p>
29     The kernel is one of the few package classes in portage that requires some
30     manual intervention to complete the upgrade. Portage will download and
31     install the kernel source for you, but then it is up to you to step in and
32     compile the new kernel before any changes will take effect.
33     </p>
34    
35     <p>
36 swift 1.4 Although this guide is targeted at users upgrading from one kernel release
37 swift 1.1 to another, it will also be useful for users migrating from one kernel
38     package to another.
39     </p>
40    
41     <p>
42 neysx 1.3 <c>gentoo-sources</c> is used as an example in this document, however, the
43 swift 1.1 instructions here also apply to the other packages present in our tree.
44     </p>
45    
46     </body>
47     </section>
48     </chapter>
49    
50     <chapter>
51 swift 1.4 <title>Why upgrade the kernel?</title>
52 swift 1.1 <section>
53     <body>
54    
55     <p>
56     Generally, upgrading from one minor kernel release to the next won't bring any
57 swift 1.4 major differences. There are several reasons to upgrade the kernel. One is to
58     take advantage of a specific new feature or driver; another is to be protected
59     against a security vulnerability, or just to maintain an up-to-date and healthy
60     system.
61 swift 1.1 </p>
62    
63     <p>
64     Even if you choose not to update to every new kernel revision, it is
65     recommended that you at least upgrade from time to time. It is strongly
66     recommended that you immediately upgrade to a new kernel if that new release
67     solves a security problem.
68     </p>
69    
70     </body>
71     </section>
72     </chapter>
73    
74     <chapter>
75     <title>Obtaining the newer sources through Portage</title>
76     <section>
77     <body>
78    
79     <p>
80     You upgrade the kernel sources like you would upgrade any other package -
81     using the <c>emerge</c> utility. It will probably be the case that you want to
82     upgrade your kernel when you see the upgrade appearing on your world updates
83     list. For example:
84     </p>
85    
86     <pre caption="New kernel sources appearing on update list">
87     # <i>emerge -Dup world</i>
88     Calculating dependencies ...done!
89 neysx 1.3 [ebuild NS ] sys-kernel/gentoo-sources-2.6.9-r2 [2.6.8-r5]
90 swift 1.1 </pre>
91    
92 neysx 1.3 <note>
93     The "NS" label in the above output means that the new kernel will be installed
94     in a New Slot, i.e. the sources of your old kernel will be kept around, until
95     you manually remove them.
96     </note>
97    
98 swift 1.1 <p>
99     You can then go ahead and install the update, e.g.:
100     </p>
101    
102     <pre caption="Upgrading your kernel sources">
103 neysx 1.3 # <i>emerge -u gentoo-sources</i>
104 swift 1.1 </pre>
105    
106     <p>
107     The kernel sources will then be installed into a subdirectory of
108 swift 1.4 <path>/usr/src</path>. In the above example, the new kernel sources will be
109 swift 1.1 installed at <path>/usr/src/linux-2.6.9-gentoo-r2</path>.
110     </p>
111    
112     </body>
113     </section>
114     </chapter>
115    
116     <chapter>
117     <title>Updating the /usr/src/linux symbolic link</title>
118     <section>
119     <body>
120    
121     <p>
122 neysx 1.8 Gentoo requires that the <path>/usr/src/linux</path> symbolic link points to
123     the sources of the kernel you are running.
124 swift 1.1 </p>
125    
126     <p>
127 neysx 1.8 Portage can update the symlink automatically when you emerge new kernel
128     sources. All you have to do is add the <c>symlink</c> flag to the USE variable
129     in <path>/etc/make.conf</path>.
130 swift 1.1 </p>
131    
132 neysx 1.8 <pre caption="Example of USE variable in /etc/make.conf">
133     <comment>(Add the symlink keyword)</comment>
134     USE="<i>symlink</i> x86 3dnow 3dnowex X aac aalib adns alsa apache2"
135     </pre>
136    
137     <p>
138     If you really want to do it yourself, the following example shows you how to
139     make the link point to <path>linux-2.6.9-gentoo-r2</path>:
140     </p>
141    
142     <pre caption="Updating the /usr/src/linux softlink manually">
143 swift 1.1 # <i>cd /usr/src</i>
144 swift 1.2 # <i>ln -sfn linux-2.6.9-gentoo-r2 linux</i>
145 swift 1.1 </pre>
146    
147     </body>
148     </section>
149     </chapter>
150    
151     <chapter id="install">
152     <title>Configuring, compiling and installing the new kernel</title>
153     <section>
154     <body>
155    
156     <p>
157     For either of these options, you should refer to the instructions given in the
158 swift 1.6 <uri link="/doc/en/handbook/index.xml">Gentoo
159 swift 1.1 Handbook</uri> relating to <e>Configuring the Kernel</e> and <e>Configuring
160 swift 1.4 the Bootloader</e>. Below is an outline of the required actions:
161 swift 1.1 </p>
162    
163     </body>
164     </section>
165     <section>
166     <title>Option 1: Automatic kernel setup with Genkernel</title>
167     <body>
168    
169     <p>
170     If you are a genkernel user, you just need to repeat the stages you went
171     through when installing your kernel for the first time.
172     </p>
173    
174     <p>
175     Simply run genkernel in the normal way:
176     </p>
177    
178     <pre caption="Invoking genkernel">
179 swift 1.7 <comment>(For 2.4 kernels:)</comment>
180 swift 1.1 # <i>genkernel all</i>
181 swift 1.7
182     <comment>(For 2.6 kernels:)</comment>
183     # <i>genkernel --udev all</i>
184 swift 1.1 </pre>
185    
186     <p>
187     You can also use extra parameters for other genkernel functionality. For
188     example, if you wish to configure some extra kernel options using
189     <c>menuconfig</c> and you wish genkernel to automatically update your grub
190 swift 1.5 boot loader configuration, then invoke genkernel as follows:
191 swift 1.1 </p>
192    
193     <pre caption="Invoking genkernel with some common arguments">
194     # <i>genkernel --menuconfig --bootloader=grub all</i>
195     </pre>
196    
197     <p>
198     For more info, follow the
199 swift 1.6 <uri link="/doc/en/genkernel.xml">Gentoo Linux Genkernel
200 swift 1.4 Guide</uri>, or refer to the <uri link="/doc/en/handbook/index.xml">Gentoo
201     Handbook</uri>. Many of the options can be set in the configuration file for
202 swift 1.6 <c>genkernel</c>, <path>/etc/genkernel.conf</path>.
203 swift 1.1 </p>
204    
205     </body>
206     </section>
207     <section>
208     <title>Option 2: Manual configuration</title>
209     <body>
210    
211     <p>
212     To begin, open the <c>menuconfig</c> utility in the kernel source tree:
213     </p>
214    
215     <pre caption="Invoking menuconfig">
216     # <i>cd /usr/src/linux</i>
217     # <i>make menuconfig</i>
218     </pre>
219    
220     <p>
221 swift 1.4 Select the options required for your hardware and operating environment. For
222     additional information on kernel configuration, refer to the chapter entitled
223     <e>Configuring the Kernel</e> of the <uri
224     link="/doc/en/handbook/index.xml">Gentoo Handbook</uri>.
225 swift 1.1 </p>
226    
227     <p>
228     Next, compile your kernel and copy it over to your boot partition. Again,
229 swift 1.4 follow the <uri link="/doc/en/handbook/index.xml">Gentoo Handbook</uri>
230     instructions outlined in the chapter on <e>Configuring the Bootloader</e>. If
231     <path>/boot</path> is a separate partition, ensure it is mounted before copying
232     the compiled kernel to this directory! Failing to do so would keep you from
233     booting the system with your new kernel.
234 swift 1.1 </p>
235    
236     <pre caption="Compiling and installing the new kernel">
237     # <i>make &amp;&amp; make modules_install</i>
238     # <i>mount /boot</i>
239     # <i>cp arch/i386/boot/bzImage /boot/bzImage-2.6.9-gentoo-r2</i>
240     # <i>cp System.map /boot/System.map-2.6.9-gentoo-r2</i>
241     </pre>
242    
243     <p>
244 swift 1.5 Finally, you should update your boot loader configuration, adding an entry for
245     the new kernel (don't delete the old one just yet!) and unmount the
246 swift 1.4 <path>/boot</path> partition. Again, refer to the
247     <uri link="/doc/en/handbook/index.xml">Gentoo Handbook</uri>
248     for detailed instructions on this procedure.
249 swift 1.1 </p>
250    
251     </body>
252     </section>
253     </chapter>
254    
255     <chapter>
256     <title>Reinstalling external modules</title>
257     <section>
258     <body>
259    
260     <p>
261     If you use any kernel modules that are not included in the kernel source tree
262 swift 1.4 but are provided elsewhere in portage (e.g. NVIDIA or ATI graphics drivers),
263     then you must reinstall these after upgrading the kernel. This is as simple as
264     re-merging the packages involved. For more information, refer to the chapter on
265     <e>Configuring the Kernel</e> in the <uri
266     link="/doc/en/handbook/index.xml">Gentoo Handbook</uri>.
267     To ensure these packages will build against the source tree at
268     <path>/usr/src/linux</path>, first uninstall the packages, then re-emerge them.
269     If old sources for these packages are kept by portage, this uninstall/re-emerge
270     procedure will make sure that they are rebuilt to work with the new kernel.
271 swift 1.1 </p>
272    
273     </body>
274     </section>
275     </chapter>
276    
277     <chapter>
278     <title>Rebooting into the new kernel</title>
279     <section>
280     <body>
281    
282     <p>
283     Next, close all applications and reboot your system. If you followed the above
284 swift 1.5 instructions correctly, the boot loader menu should include an entry for the
285 swift 1.4 new kernel. Select the new kernel and let the system boot.
286 swift 1.1 </p>
287    
288     <p>
289 swift 1.4 Hopefully, your system successfully boots with the new kernel, and you can log
290     in to resume whatever you were doing. If this is the case, then the upgrade is
291     complete.
292 swift 1.1 </p>
293    
294     <p>
295 swift 1.4 If you made a mistake and the system fails to boot with the new kernel, reboot
296 swift 1.5 the system and select the entry from the boot loader that corresponds to the
297 swift 1.4 last known working kernel. You can then restart from the <uri link="#install">
298     Configuring, compiling, and installing the new kernel</uri> stage -- making
299     the appropriate changes to correct your mistake. In some cases, you might not
300     even need to reboot to do this (e.g. you missed a driver for an audio device,
301 swift 1.5 Ethernet adapter, etc.)
302 swift 1.1 </p>
303    
304     </body>
305     </section>
306     </chapter>
307    
308     <chapter>
309     <title>Running multiple kernels</title>
310     <section>
311     <body>
312    
313     <p>
314     You may have noticed, that when installing the sources for your newer kernel,
315 swift 1.4 the sources for your existing kernel were not removed. This is by design -- it
316 swift 1.1 allows you to easily switch between running different kernels.
317     </p>
318    
319     <p>
320     Switching between multiple kernels is as simple as leaving the kernel sources
321     under <path>/usr/src/</path> and leaving the <path>bzImage</path> binaries on
322 swift 1.5 your <path>/boot</path> partition (referenced by entries in your boot loader
323     configuration). Every time you boot up, you will be presented with a choice of
324     which kernel to boot into.
325 swift 1.1 </p>
326    
327     </body>
328     </section>
329     </chapter>
330    
331     <chapter>
332     <title>Removing older kernels</title>
333     <section>
334     <body>
335    
336     <p>
337     Continuing on from the last section, you may be happy with your new kernel and
338     not have any need to keep older kernel versions around. To easily remove all
339     sources for a particular kernel except for the newest one, you can take
340 swift 1.4 advantage of the <e>prune</e> option available through <c>emerge</c>. Continuing
341     the example using <c>gentoo-sources</c>:
342 swift 1.1 </p>
343    
344     <pre caption="Pruning old versions">
345 neysx 1.3 # <i>emerge -P gentoo-sources</i>
346 swift 1.1 </pre>
347    
348     <p>
349     In most cases, temporary files used during compilation will still remain under
350     the appropriate source directory under <path>/usr/src</path>. It is safe to
351     remove these using <c>rm</c>.
352     </p>
353    
354     <p>
355     You can also safely delete any modules that were used by this kernel. This can
356     be done by removing the appropriate directories under <path>/lib/modules/</path>
357     that relate to the kernel versions you are removing. Be careful not to delete
358     modules belonging to kernels that you still use!
359     </p>
360    
361     <p>
362     Finally, you can mount your <path>/boot</path> partition and remove the
363     <path>bzImage</path> and <path>System.map</path> files for the kernel(s)
364 swift 1.5 you are pruning. You should also edit your boot loader configuration so that it
365 swift 1.4 no longer references such kernel(s).
366 swift 1.1 </p>
367    
368     </body>
369     </section>
370     </chapter>
371    
372     <chapter>
373 neysx 1.3 <title>Advanced: Using your old kernel .config to configure a new one</title>
374     <section>
375     <body>
376    
377     <p>
378     It is sometimes possible to save time by re-using the configuration file from
379     your old kernel when configuring the new one. Note that this is generally
380 swift 1.4 unsafe -- too many changes between every kernel release for this to be a
381 neysx 1.3 reliable upgrade path.
382     </p>
383    
384     <p>
385     The only situation where this is appropriate is when upgrading from one Gentoo
386     kernel revision to another. For example, the changes made between
387     <c>gentoo-sources-2.6.9-r1</c> and <c>gentoo-sources-2.6.9-r2</c> will be very
388     small, so it is usually OK to use the following method. However, it is not
389     appropriate to use it in the example used throughout this document: upgrading
390     from 2.6.8 to 2.6.9. Too many changes between the official releases, and the
391     method described below does not display enough context to the user, often
392     resulting in the user running into problems because they disabled options that
393     they really didn't want to.
394     </p>
395    
396     <p>
397 swift 1.5 To reuse your old <path>.config</path>, you simply need to copy it over and then
398     run <c>make oldconfig</c>. In the following example, we take the configuration
399     from <c>gentoo-sources-2.6.9-r1</c> and import it into
400 neysx 1.3 <c>gentoo-sources-2.6.9-r2</c>.
401     </p>
402    
403     <pre caption="Reusing your old config">
404     # <i>cd /usr/src/linux-2.6.9-gentoo-r2</i>
405     # <i>cp ../linux-2.6.9-gentoo-r1/.config .</i>
406     # <i>make oldconfig</i>
407     </pre>
408    
409     <p>
410     At this point, you may be asked to produce answers for configuration options
411     which have changed between the two versions. Once you have done that, you can
412     compile and install your kernel as normal, without having to go through the
413     <c>menuconfig</c> configuration process.
414     </p>
415    
416     </body>
417     </section>
418     </chapter>
419    
420     <chapter>
421 swift 1.1 <title>Problems after a kernel upgrade?</title>
422     <section>
423     <body>
424    
425     <p>
426     With the rapid development of the Linux kernel, it is inevitable that some
427 neysx 1.3 changes made from one kernel release to another may cause some problems. If you
428     have any issues with the latest versions of <uri
429     link="/doc/en/gentoo-kernel.xml#doc_chap2"> Gentoo-supported kernels</uri> then
430     please do report the issues to us.
431 swift 1.1 </p>
432    
433     </body>
434     </section>
435     </chapter>
436    
437     </guide>

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