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1 swift 1.1 <?xml version="1.0" encoding="UTF-8"?>
2 swift 1.5 <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/kernel-upgrade.xml,v 1.4 2005/05/23 18:35:47 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 swift 1.4 <version>0.1.3</version>
21     <date>2005-05-23</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     Gentoo requires you to maintain a symbolic link, located at
123     <path>/usr/src/linux</path>. This should point to the sources of the
124     kernel you are running.
125     </p>
126    
127     <p>
128 swift 1.4 In any case, we need to update the symbolic link to point at the kernel
129 swift 1.1 sources that we are about to upgrade to. Continuing our example:
130     </p>
131    
132     <pre caption="Updating the /usr/src/linux softlink">
133     # <i>cd /usr/src</i>
134 swift 1.2 # <i>ln -sfn linux-2.6.9-gentoo-r2 linux</i>
135 swift 1.1 </pre>
136    
137     </body>
138     </section>
139     </chapter>
140    
141     <chapter id="install">
142     <title>Configuring, compiling and installing the new kernel</title>
143     <section>
144     <body>
145    
146     <p>
147     For either of these options, you should refer to the instructions given in the
148     <uri link="http://www.gentoo.org/doc/en/handbook/index.xml">Gentoo
149     Handbook</uri> relating to <e>Configuring the Kernel</e> and <e>Configuring
150 swift 1.4 the Bootloader</e>. Below is an outline of the required actions:
151 swift 1.1 </p>
152    
153     </body>
154     </section>
155     <section>
156     <title>Option 1: Automatic kernel setup with Genkernel</title>
157     <body>
158    
159     <p>
160     If you are a genkernel user, you just need to repeat the stages you went
161     through when installing your kernel for the first time.
162     </p>
163    
164     <p>
165     Simply run genkernel in the normal way:
166     </p>
167    
168     <pre caption="Invoking genkernel">
169     # <i>genkernel all</i>
170     </pre>
171    
172     <p>
173     You can also use extra parameters for other genkernel functionality. For
174     example, if you wish to configure some extra kernel options using
175     <c>menuconfig</c> and you wish genkernel to automatically update your grub
176 swift 1.5 boot loader configuration, then invoke genkernel as follows:
177 swift 1.1 </p>
178    
179     <pre caption="Invoking genkernel with some common arguments">
180     # <i>genkernel --menuconfig --bootloader=grub all</i>
181     </pre>
182    
183     <p>
184     For more info, follow the
185     <uri link="http://www.gentoo.org/doc/en/genkernel.xml">Gentoo Linux Genkernel
186 swift 1.4 Guide</uri>, or refer to the <uri link="/doc/en/handbook/index.xml">Gentoo
187     Handbook</uri>. Many of the options can be set in the configuration file for
188     <uri link="/doc/en/genkernel.xml">genkernel</uri>,
189     <path>/etc/genkernel.conf</path>.
190 swift 1.1 </p>
191    
192     </body>
193     </section>
194     <section>
195     <title>Option 2: Manual configuration</title>
196     <body>
197    
198     <p>
199     To begin, open the <c>menuconfig</c> utility in the kernel source tree:
200     </p>
201    
202     <pre caption="Invoking menuconfig">
203     # <i>cd /usr/src/linux</i>
204     # <i>make menuconfig</i>
205     </pre>
206    
207     <p>
208 swift 1.4 Select the options required for your hardware and operating environment. For
209     additional information on kernel configuration, refer to the chapter entitled
210     <e>Configuring the Kernel</e> of the <uri
211     link="/doc/en/handbook/index.xml">Gentoo Handbook</uri>.
212 swift 1.1 </p>
213    
214     <p>
215     Next, compile your kernel and copy it over to your boot partition. Again,
216 swift 1.4 follow the <uri link="/doc/en/handbook/index.xml">Gentoo Handbook</uri>
217     instructions outlined in the chapter on <e>Configuring the Bootloader</e>. If
218     <path>/boot</path> is a separate partition, ensure it is mounted before copying
219     the compiled kernel to this directory! Failing to do so would keep you from
220     booting the system with your new kernel.
221 swift 1.1 </p>
222    
223     <pre caption="Compiling and installing the new kernel">
224     # <i>make &amp;&amp; make modules_install</i>
225     # <i>mount /boot</i>
226     # <i>cp arch/i386/boot/bzImage /boot/bzImage-2.6.9-gentoo-r2</i>
227     # <i>cp System.map /boot/System.map-2.6.9-gentoo-r2</i>
228     </pre>
229    
230     <p>
231 swift 1.5 Finally, you should update your boot loader configuration, adding an entry for
232     the new kernel (don't delete the old one just yet!) and unmount the
233 swift 1.4 <path>/boot</path> partition. Again, refer to the
234     <uri link="/doc/en/handbook/index.xml">Gentoo Handbook</uri>
235     for detailed instructions on this procedure.
236 swift 1.1 </p>
237    
238     </body>
239     </section>
240     </chapter>
241    
242     <chapter>
243     <title>Reinstalling external modules</title>
244     <section>
245     <body>
246    
247     <p>
248     If you use any kernel modules that are not included in the kernel source tree
249 swift 1.4 but are provided elsewhere in portage (e.g. NVIDIA or ATI graphics drivers),
250     then you must reinstall these after upgrading the kernel. This is as simple as
251     re-merging the packages involved. For more information, refer to the chapter on
252     <e>Configuring the Kernel</e> in the <uri
253     link="/doc/en/handbook/index.xml">Gentoo Handbook</uri>.
254     To ensure these packages will build against the source tree at
255     <path>/usr/src/linux</path>, first uninstall the packages, then re-emerge them.
256     If old sources for these packages are kept by portage, this uninstall/re-emerge
257     procedure will make sure that they are rebuilt to work with the new kernel.
258 swift 1.1 </p>
259    
260     </body>
261     </section>
262     </chapter>
263    
264     <chapter>
265     <title>Rebooting into the new kernel</title>
266     <section>
267     <body>
268    
269     <p>
270     Next, close all applications and reboot your system. If you followed the above
271 swift 1.5 instructions correctly, the boot loader menu should include an entry for the
272 swift 1.4 new kernel. Select the new kernel and let the system boot.
273 swift 1.1 </p>
274    
275     <p>
276 swift 1.4 Hopefully, your system successfully boots with the new kernel, and you can log
277     in to resume whatever you were doing. If this is the case, then the upgrade is
278     complete.
279 swift 1.1 </p>
280    
281     <p>
282 swift 1.4 If you made a mistake and the system fails to boot with the new kernel, reboot
283 swift 1.5 the system and select the entry from the boot loader that corresponds to the
284 swift 1.4 last known working kernel. You can then restart from the <uri link="#install">
285     Configuring, compiling, and installing the new kernel</uri> stage -- making
286     the appropriate changes to correct your mistake. In some cases, you might not
287     even need to reboot to do this (e.g. you missed a driver for an audio device,
288 swift 1.5 Ethernet adapter, etc.)
289 swift 1.1 </p>
290    
291     </body>
292     </section>
293     </chapter>
294    
295     <chapter>
296     <title>Running multiple kernels</title>
297     <section>
298     <body>
299    
300     <p>
301     You may have noticed, that when installing the sources for your newer kernel,
302 swift 1.4 the sources for your existing kernel were not removed. This is by design -- it
303 swift 1.1 allows you to easily switch between running different kernels.
304     </p>
305    
306     <p>
307     Switching between multiple kernels is as simple as leaving the kernel sources
308     under <path>/usr/src/</path> and leaving the <path>bzImage</path> binaries on
309 swift 1.5 your <path>/boot</path> partition (referenced by entries in your boot loader
310     configuration). Every time you boot up, you will be presented with a choice of
311     which kernel to boot into.
312 swift 1.1 </p>
313    
314     </body>
315     </section>
316     </chapter>
317    
318     <chapter>
319     <title>Removing older kernels</title>
320     <section>
321     <body>
322    
323     <p>
324     Continuing on from the last section, you may be happy with your new kernel and
325     not have any need to keep older kernel versions around. To easily remove all
326     sources for a particular kernel except for the newest one, you can take
327 swift 1.4 advantage of the <e>prune</e> option available through <c>emerge</c>. Continuing
328     the example using <c>gentoo-sources</c>:
329 swift 1.1 </p>
330    
331     <pre caption="Pruning old versions">
332 neysx 1.3 # <i>emerge -P gentoo-sources</i>
333 swift 1.1 </pre>
334    
335     <p>
336     In most cases, temporary files used during compilation will still remain under
337     the appropriate source directory under <path>/usr/src</path>. It is safe to
338     remove these using <c>rm</c>.
339     </p>
340    
341     <p>
342     You can also safely delete any modules that were used by this kernel. This can
343     be done by removing the appropriate directories under <path>/lib/modules/</path>
344     that relate to the kernel versions you are removing. Be careful not to delete
345     modules belonging to kernels that you still use!
346     </p>
347    
348     <p>
349     Finally, you can mount your <path>/boot</path> partition and remove the
350     <path>bzImage</path> and <path>System.map</path> files for the kernel(s)
351 swift 1.5 you are pruning. You should also edit your boot loader configuration so that it
352 swift 1.4 no longer references such kernel(s).
353 swift 1.1 </p>
354    
355     </body>
356     </section>
357     </chapter>
358    
359     <chapter>
360 neysx 1.3 <title>Advanced: Using your old kernel .config to configure a new one</title>
361     <section>
362     <body>
363    
364     <p>
365     It is sometimes possible to save time by re-using the configuration file from
366     your old kernel when configuring the new one. Note that this is generally
367 swift 1.4 unsafe -- too many changes between every kernel release for this to be a
368 neysx 1.3 reliable upgrade path.
369     </p>
370    
371     <p>
372     The only situation where this is appropriate is when upgrading from one Gentoo
373     kernel revision to another. For example, the changes made between
374     <c>gentoo-sources-2.6.9-r1</c> and <c>gentoo-sources-2.6.9-r2</c> will be very
375     small, so it is usually OK to use the following method. However, it is not
376     appropriate to use it in the example used throughout this document: upgrading
377     from 2.6.8 to 2.6.9. Too many changes between the official releases, and the
378     method described below does not display enough context to the user, often
379     resulting in the user running into problems because they disabled options that
380     they really didn't want to.
381     </p>
382    
383     <p>
384 swift 1.5 To reuse your old <path>.config</path>, you simply need to copy it over and then
385     run <c>make oldconfig</c>. In the following example, we take the configuration
386     from <c>gentoo-sources-2.6.9-r1</c> and import it into
387 neysx 1.3 <c>gentoo-sources-2.6.9-r2</c>.
388     </p>
389    
390     <pre caption="Reusing your old config">
391     # <i>cd /usr/src/linux-2.6.9-gentoo-r2</i>
392     # <i>cp ../linux-2.6.9-gentoo-r1/.config .</i>
393     # <i>make oldconfig</i>
394     </pre>
395    
396     <p>
397     At this point, you may be asked to produce answers for configuration options
398     which have changed between the two versions. Once you have done that, you can
399     compile and install your kernel as normal, without having to go through the
400     <c>menuconfig</c> configuration process.
401     </p>
402    
403     </body>
404     </section>
405     </chapter>
406    
407     <chapter>
408 swift 1.1 <title>Problems after a kernel upgrade?</title>
409     <section>
410     <body>
411    
412     <p>
413     With the rapid development of the Linux kernel, it is inevitable that some
414 neysx 1.3 changes made from one kernel release to another may cause some problems. If you
415     have any issues with the latest versions of <uri
416     link="/doc/en/gentoo-kernel.xml#doc_chap2"> Gentoo-supported kernels</uri> then
417     please do report the issues to us.
418 swift 1.1 </p>
419    
420     </body>
421     </section>
422     </chapter>
423    
424     </guide>

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