Kernel/Upgrade/zh-cn

这篇文章描述了升级到新内核步骤.

Installing and using a new kernel
A kernel upgrade may be a good idea when new kernel sources are installed. New kernel sources are sometimes installed while updating the system by running emerge -a --update --deep --with-bdeps=y --newuse @world, or of course when installed directly.

Installing new kernel sources doesn't provide the user with a new kernel. It is necessary to make and install a new kernel from the new sources and then reboot the system to actually run the new kernel.

Making a new kernel from the new sources is basically the same process as making a kernel when installing the system. The difference is that one can use the configuration of the old kernel to create a configuration for the new kernel. Using the old configuration saves the user from going through all the kernel options (like make menuconfig) again.

The configuration of the kernel is saved in a file named in the directory that holds the kernel sources. A new kernel may have options or features the old kernel does not have, or it might not have a feature or option anymore which the old kernel still has. The kernel configuration specifies whether the features and options of a kernel are to be enabled or not, perhaps built into the kernel, or perhaps built as modules which can be loaded into the running kernel on demand. Hence the configuration file of the new kernel may have new entries the configuration file of the old kernel doesn't have, and it might not have entries anymore which are present in the configuration file of the old kernel.

To deal with such changes of the configuration file, the configuration file of the old kernel needs to be converted to a configuration that can be used with the new kernel. This article shows how to make a new kernel from new kernel sources with converting the configuration file of the old kernel.

Make a backup of the current kernel configuration
It is wise to make a backup of the kernel configuration so that the previous configurations are not lost. After all, many users devote considerable time to figure out the best configuration for the system, and losing that information is definitely not wanted.

It is easy to make a backup of the current kernel configuration:

Provided that the symlink to the kernel sources has been set correctly, this copies the configuration of the currently used kernel to the home directory of root, renaming the configuration to followed by the version of the current running Linux kernel.

Set symlink to new kernel sources
The symlink should always point to the directory that holds the sources of the kernel which currently runs. This can be done in one of three ways:


 * 1) Installing the kernel sources with
 * 2) Setting the link with eselect
 * 3) Manually updating the symbolic link

Installing the kernel sources with the symlink USE flag
This will make the point to the newly installed kernel sources.

If necessary, it can still be modified later with one of the other two methods.

Setting the link with eselect
To set the symlink with eselect:

This outputs the available kernel sources. The asterisk indicates the chosen sources.

To change the kernel sources, e.g. to the second entry, do:

Manually updating the symbolic link
To set the symbolic link manually:

Copy previous kernel configuration
The configuration of the old kernel needs to be copied to the new one. It can be found in several places:


 * In the procfs filesystem, if the kernel option Enable access to .config through /proc/config.gz was activated in the present kernel:


 * In the directory, if the configuration was installed installed there:


 * In the kernel directory of the currently-running kernel:

Configure the new kernel
To use the configuration of the old kernel with the new kernel, it needs to be converted. The conversion can be done by running either make silentoldconfig or make olddefconfig.

make silentoldconfig gives choices for new options, make olddefconfig does not. Use either, not both.

make silentoldconfig
The following configuration is like the text based configuration with make config. For new configuration options, it gives a choice. For example:

The string (NEW) at the end of the line marks this option as new. Left to the string in square brackets are the possible answers: Yes, no, module or ? to show the help. The recommend answer is capitalized (here Y). The help explains the option or driver.

Unfortunately make silentoldconfig</tt> doesn't show - next to the help - a lot more information for each option, like the context, so that it is sometimes difficult to give the right answer. In this case the best way to go is to remember the option name and revise it afterwards through one of the graphical kernel configuration tools.

make olddefconfig
If interactivity is not wanted (no questions should be asked), then use make olddefconfig</tt>:

编译
这一步请参考 manual configuration.

重新安装外部内核模块
任何外部的内核模块，像 binary kernel modules, 需要为新的内核重新编译. 如果新内核还没有编译，需要首先为编译外部内核模块做准备：

你可以使用"@module-rebuild"命令重新编译包：

Solving build problems
When experiencing build problems while rebuilding the current kernel, it might help to sanitize the kernel sources. Make sure to backup the file first, as the operation will remove it. Make sure not to use a or  suffix as backup as make distclean</tt> will clean those up as well.

删除旧内核
参考 kernel removal.

外部资源

 * kernel changelog with some explanations of new features