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<?xml version="1.0" encoding="UTF-8"?> |
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<!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/kernel-upgrade.xml,v 1.11 2005/10/11 03:48:06 swift Exp $ --> |
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|
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<!DOCTYPE guide SYSTEM "/dtd/guide.dtd"> |
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<guide link="/doc/en/kernel-upgrade.xml"> |
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<title>Gentoo Linux Kernel Upgrade Guide</title> |
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<author title="Author"> |
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<mail link="dsd@gentoo.org">Daniel Drake</mail> |
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</author> |
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|
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<abstract> |
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This document describes the process of upgrading your kernel from one release |
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to another. |
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</abstract> |
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|
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<!-- The content of this document is licensed under the CC-BY-SA license --> |
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<!-- See http://creativecommons.org/licenses/by-sa/2.5 --> |
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<license/> |
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|
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<version>0.1.8</version> |
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<date>2005-10-11</date> |
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|
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<chapter> |
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<title>Introduction</title> |
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<section> |
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<body> |
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|
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<p> |
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The kernel is one of the few package classes in portage that requires some |
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manual intervention to complete the upgrade. Portage will download and |
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install the kernel source for you, but then it is up to you to step in and |
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compile the new kernel before any changes will take effect. |
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</p> |
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|
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<p> |
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Although this guide is targeted at users upgrading from one kernel release |
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to another, it will also be useful for users migrating from one kernel |
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package to another. |
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</p> |
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|
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<p> |
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<c>gentoo-sources</c> is used as an example in this document, however, the |
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instructions here also apply to the other packages present in our tree. |
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</p> |
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|
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</body> |
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</section> |
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</chapter> |
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|
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<chapter> |
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<title>Why upgrade the kernel?</title> |
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<section> |
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<body> |
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|
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<p> |
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Generally, upgrading from one minor kernel release to the next won't bring any |
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major differences. There are several reasons to upgrade the kernel. One is to |
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take advantage of a specific new feature or driver; another is to be protected |
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against a security vulnerability, or just to maintain an up-to-date and healthy |
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system. |
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</p> |
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|
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<p> |
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Even if you choose not to update to every new kernel revision, it is |
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recommended that you at least upgrade from time to time. It is strongly |
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recommended that you immediately upgrade to a new kernel if that new release |
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solves a security problem. |
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</p> |
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|
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</body> |
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</section> |
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</chapter> |
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|
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<chapter> |
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<title>Obtaining the newer sources through Portage</title> |
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<section> |
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<body> |
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|
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<p> |
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You upgrade the kernel sources like you would upgrade any other package - |
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using the <c>emerge</c> utility. It will probably be the case that you want to |
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upgrade your kernel when you see the upgrade appearing on your world updates |
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list. For example: |
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</p> |
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|
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<pre caption="New kernel sources appearing on update list"> |
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# <i>emerge -Dup world</i> |
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Calculating dependencies ...done! |
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[ebuild NS ] sys-kernel/gentoo-sources-2.6.9-r2 [2.6.8-r5] |
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</pre> |
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|
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<note> |
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The "NS" label in the above output means that the new kernel will be installed |
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in a New Slot, i.e. the sources of your old kernel will be kept around, until |
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you manually remove them. |
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</note> |
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|
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<p> |
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You can then go ahead and install the update, e.g.: |
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</p> |
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|
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<pre caption="Upgrading your kernel sources"> |
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# <i>emerge -u gentoo-sources</i> |
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</pre> |
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|
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<p> |
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The kernel sources will then be installed into a subdirectory of |
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<path>/usr/src</path>. In the above example, the new kernel sources will be |
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installed at <path>/usr/src/linux-2.6.9-gentoo-r2</path>. |
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</p> |
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|
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</body> |
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</section> |
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</chapter> |
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|
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<chapter> |
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<title>Updating the /usr/src/linux symbolic link</title> |
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<section> |
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<body> |
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|
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<p> |
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Gentoo requires that the <path>/usr/src/linux</path> symbolic link points to |
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the sources of the kernel you are running. |
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</p> |
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|
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<p> |
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Portage can update the symlink automatically when you emerge new kernel |
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sources. All you have to do is add the <c>symlink</c> flag to the USE variable |
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in <path>/etc/make.conf</path>. |
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</p> |
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|
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<pre caption="Example of USE variable in /etc/make.conf"> |
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<comment>(Add the symlink keyword)</comment> |
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USE="<i>symlink</i> x86 3dnow 3dnowex X aac aalib adns alsa apache2" |
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</pre> |
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|
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<p> |
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If you really want to do it yourself, the following example shows you how to |
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make the link point to <path>linux-2.6.9-gentoo-r2</path>: |
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</p> |
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|
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<pre caption="Updating the /usr/src/linux softlink manually"> |
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# <i>cd /usr/src</i> |
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# <i>ln -sfn linux-2.6.9-gentoo-r2 linux</i> |
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</pre> |
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|
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</body> |
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</section> |
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</chapter> |
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|
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<chapter id="install"> |
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<title>Configuring, compiling and installing the new kernel</title> |
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<section> |
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<body> |
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|
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<p> |
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For either of these options, you should refer to the instructions given in the |
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<uri link="/doc/en/handbook/index.xml">Gentoo |
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Handbook</uri> relating to <e>Configuring the Kernel</e> and <e>Configuring |
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the Bootloader</e>. Below is an outline of the required actions: |
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</p> |
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|
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</body> |
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</section> |
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<section> |
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<title>Option 1: Automatic kernel setup with Genkernel</title> |
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<body> |
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|
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<p> |
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If you are a genkernel user, you just need to repeat the stages you went |
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through when installing your kernel for the first time. |
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</p> |
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|
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<p> |
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Simply run genkernel in the normal way: |
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</p> |
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|
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<pre caption="Invoking genkernel"> |
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<comment>(For 2.4 kernels:)</comment> |
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# <i>genkernel all</i> |
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|
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<comment>(For 2.6 kernels:)</comment> |
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# <i>genkernel --udev all</i> |
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</pre> |
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|
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<p> |
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You can also use extra parameters for other genkernel functionality. For |
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example, if you wish to configure some extra kernel options using |
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<c>menuconfig</c> and you wish genkernel to automatically update your grub |
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boot loader configuration, then invoke genkernel as follows: |
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</p> |
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|
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<pre caption="Invoking genkernel with some common arguments"> |
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# <i>genkernel --menuconfig --bootloader=grub all</i> |
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</pre> |
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|
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<p> |
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For more info, follow the |
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<uri link="/doc/en/genkernel.xml">Gentoo Linux Genkernel |
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Guide</uri>, or refer to the <uri link="/doc/en/handbook/index.xml">Gentoo |
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Handbook</uri>. Many of the options can be set in the configuration file for |
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<c>genkernel</c>, <path>/etc/genkernel.conf</path>. |
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</p> |
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|
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</body> |
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</section> |
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<section> |
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<title>Option 2: Manual configuration</title> |
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<body> |
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|
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<p> |
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To begin, open the <c>menuconfig</c> utility in the kernel source tree: |
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</p> |
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|
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<pre caption="Invoking menuconfig"> |
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# <i>cd /usr/src/linux</i> |
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# <i>make menuconfig</i> |
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</pre> |
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|
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<p> |
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Select the options required for your hardware and operating environment. For |
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additional information on kernel configuration, refer to the chapter entitled |
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<e>Configuring the Kernel</e> of the <uri |
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link="/doc/en/handbook/index.xml">Gentoo Handbook</uri>. |
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</p> |
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|
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<p> |
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Next, compile your kernel and copy it over to your boot partition. Again, |
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follow the <uri link="/doc/en/handbook/index.xml">Gentoo Handbook</uri> |
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instructions outlined in the chapter on <e>Configuring the Bootloader</e>. If |
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<path>/boot</path> is a separate partition, ensure it is mounted before copying |
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the compiled kernel to this directory! Failing to do so would keep you from |
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booting the system with your new kernel. |
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</p> |
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|
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<pre caption="Compiling and installing the new kernel"> |
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# <i>make && make modules_install</i> |
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# <i>mount /boot</i> |
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# <i>cp arch/i386/boot/bzImage /boot/bzImage-2.6.9-gentoo-r2</i> |
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</pre> |
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|
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<p> |
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Finally, you should update your boot loader configuration, adding an entry for |
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the new kernel (don't delete the old one just yet!) and unmount the |
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<path>/boot</path> partition. Again, refer to the |
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<uri link="/doc/en/handbook/index.xml">Gentoo Handbook</uri> |
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for detailed instructions on this procedure. |
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</p> |
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|
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</body> |
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</section> |
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</chapter> |
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|
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<chapter> |
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<title>Reinstalling external modules</title> |
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<section> |
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<body> |
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|
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<p> |
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If you use any kernel modules that are not included in the kernel source tree |
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but are provided elsewhere in portage (e.g. NVIDIA or ATI graphics drivers), |
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then you must reinstall these after upgrading the kernel. This is as simple as |
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re-merging the packages involved. For more information, refer to the chapter on |
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<e>Configuring the Kernel</e> in the <uri |
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link="/doc/en/handbook/index.xml">Gentoo Handbook</uri>. |
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To ensure these packages will build against the source tree at |
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<path>/usr/src/linux</path>, first uninstall the packages, then re-emerge them. |
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If old sources for these packages are kept by portage, this uninstall/re-emerge |
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procedure will make sure that they are rebuilt to work with the new kernel. |
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</p> |
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|
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<p> |
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We provide you with an easy tool (<c>sys-kernel/module-rebuild</c>) which |
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rebuilds all the kernel modules you have installed using separate ebuilds. |
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</p> |
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|
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</body> |
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</section> |
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</chapter> |
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|
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<chapter> |
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<title>Rebooting into the new kernel</title> |
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<section> |
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<body> |
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|
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<p> |
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Next, close all applications and reboot your system. If you followed the above |
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instructions correctly, the boot loader menu should include an entry for the |
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new kernel. Select the new kernel and let the system boot. |
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</p> |
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|
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<p> |
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Hopefully, your system successfully boots with the new kernel, and you can log |
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in to resume whatever you were doing. If this is the case, then the upgrade is |
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complete. |
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</p> |
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|
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<p> |
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If you made a mistake and the system fails to boot with the new kernel, reboot |
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the system and select the entry from the boot loader that corresponds to the |
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last known working kernel. You can then restart from the <uri link="#install"> |
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Configuring, compiling, and installing the new kernel</uri> stage -- making |
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the appropriate changes to correct your mistake. In some cases, you might not |
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even need to reboot to do this (e.g. you missed a driver for an audio device, |
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Ethernet adapter, etc.) |
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</p> |
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|
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</body> |
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</section> |
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</chapter> |
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|
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<chapter> |
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<title>Running multiple kernels</title> |
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<section> |
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<body> |
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|
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<p> |
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You may have noticed, that when installing the sources for your newer kernel, |
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the sources for your existing kernel were not removed. This is by design -- it |
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allows you to easily switch between running different kernels. |
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</p> |
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|
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<p> |
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Switching between multiple kernels is as simple as leaving the kernel sources |
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under <path>/usr/src/</path> and leaving the <path>bzImage</path> binaries on |
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your <path>/boot</path> partition (referenced by entries in your boot loader |
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configuration). Every time you boot up, you will be presented with a choice of |
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which kernel to boot into. |
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</p> |
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|
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</body> |
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</section> |
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</chapter> |
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|
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<chapter> |
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<title>Removing older kernels</title> |
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<section> |
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<body> |
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|
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<p> |
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Continuing on from the last section, you may be happy with your new kernel and |
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not have any need to keep older kernel versions around. To easily remove all |
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sources for a particular kernel except for the newest one, you can take |
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advantage of the <e>prune</e> option available through <c>emerge</c>. Continuing |
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the example using <c>gentoo-sources</c>: |
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</p> |
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|
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<pre caption="Pruning old versions"> |
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# <i>emerge -P gentoo-sources</i> |
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</pre> |
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|
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<p> |
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In most cases, temporary files used during compilation will still remain under |
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the appropriate source directory under <path>/usr/src</path>. It is safe to |
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remove these using <c>rm</c>. |
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</p> |
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|
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<p> |
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You can also safely delete any modules that were used by this kernel. This can |
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be done by removing the appropriate directories under <path>/lib/modules/</path> |
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that relate to the kernel versions you are removing. Be careful not to delete |
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modules belonging to kernels that you still use! |
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</p> |
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|
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<p> |
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Finally, you can mount your <path>/boot</path> partition and remove the |
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<path>bzImage</path> file(s) for the kernel(s) you are pruning. You should also |
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edit your boot loader configuration so that it no longer references such |
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kernel(s). |
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</p> |
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|
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</body> |
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</section> |
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</chapter> |
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|
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<chapter> |
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<title>Advanced: Using your old kernel .config to configure a new one</title> |
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<section> |
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<body> |
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|
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<p> |
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It is sometimes possible to save time by re-using the configuration file from |
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your old kernel when configuring the new one. Note that this is generally |
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unsafe -- too many changes between every kernel release for this to be a |
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reliable upgrade path. |
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</p> |
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|
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<p> |
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The only situation where this is appropriate is when upgrading from one Gentoo |
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kernel revision to another. For example, the changes made between |
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<c>gentoo-sources-2.6.9-r1</c> and <c>gentoo-sources-2.6.9-r2</c> will be very |
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small, so it is usually OK to use the following method. However, it is not |
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appropriate to use it in the example used throughout this document: upgrading |
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from 2.6.8 to 2.6.9. Too many changes between the official releases, and the |
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method described below does not display enough context to the user, often |
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resulting in the user running into problems because they disabled options that |
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they really didn't want to. |
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</p> |
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|
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<p> |
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To reuse your old <path>.config</path>, you simply need to copy it over and then |
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run <c>make oldconfig</c>. In the following example, we take the configuration |
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from <c>gentoo-sources-2.6.9-r1</c> and import it into |
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<c>gentoo-sources-2.6.9-r2</c>. |
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</p> |
| 406 |
|
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<pre caption="Reusing your old config"> |
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# <i>cd /usr/src/linux-2.6.9-gentoo-r2</i> |
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# <i>cp ../linux-2.6.9-gentoo-r1/.config .</i> |
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# <i>make oldconfig</i> |
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</pre> |
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|
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<p> |
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At this point, you may be asked to produce answers for configuration options |
| 415 |
which have changed between the two versions. Once you have done that, you can |
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compile and install your kernel as normal, without having to go through the |
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<c>menuconfig</c> configuration process. |
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</p> |
| 419 |
|
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</body> |
| 421 |
</section> |
| 422 |
</chapter> |
| 423 |
|
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<chapter> |
| 425 |
<title>Problems after a kernel upgrade?</title> |
| 426 |
<section> |
| 427 |
<body> |
| 428 |
|
| 429 |
<p> |
| 430 |
With the rapid development of the Linux kernel, it is inevitable that some |
| 431 |
changes made from one kernel release to another may cause some problems. If you |
| 432 |
have any issues with the latest versions of <uri |
| 433 |
link="/doc/en/gentoo-kernel.xml#doc_chap2"> Gentoo-supported kernels</uri> then |
| 434 |
please do report the issues to us. |
| 435 |
</p> |
| 436 |
|
| 437 |
</body> |
| 438 |
</section> |
| 439 |
</chapter> |
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|
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</guide> |
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