2 - Raspberry PI Community Projects

8.10.1. Introduction and Prerequisites
Debian manages the kernel in the form of a package, which is not how kernels have traditionally
been compiled and installed. Specific tools have therefore been developed for this purpose.
They allow easy creation of a Debian package from Linux kernel sources, possibly adding patches
along the way. Since the kernel remains under the control of the packaging system, it can then
be removed cleanly, or deployed on several machines. Furthermore, the scripts associated with
these packages automate the interaction with the bootloader.
To compile a Linux kernel the Debian way, you will need to use the tools included in the kernelpackage
package. Furthermore, the configuration step for the kernel requires the libncurses5-dev
package. Finally, the fakeroot package will enable creation of the Debian package without using
administrator's rights.
8.10.2. Geing the Sources
Like anything that can be useful on a Debian system, the Linux kernel sources are available
in a package. To retrieve them, just install the linux-source-version package. The apt-cache
search ˆlinux-source command lists the various kernel versions packaged by Debian. The
latest version is available in the Unstable distribution: you can retrieve them without much risk
(especially if your APT is configured according to the instructions of Section 6.2.6, “Working
with Several Distributions” (page 113)). Note that the source code contained in these packages
does not correspond precisely with that published by Linus Torvalds and the kernel developers;
like all distributions, Debian applies a number of patches. These modifications include patches
(some relevant to security problems) that are waiting to be included in the next version of the
kernel, as well as some features that are specific to Debian (like cramfs, a filesystem specifically
for the initrd image).
CULTURE
Names of kernel packages
Historically, packages containing the Debian kernel were called kernel-image-
*, but they all actually contained a Linux kernel. Since Debian works with
other kernels (Hurd or FreeBSD, for example), this was confusing. Nowadays,
the packages are called “linux-image-*"; the kernel-image-* packages
are now empty shells and their only purpose is to facilitate the transition.
Source packages for the Linux kernel are also called “linux-source-*”. As for
packages containing patches, the transition is still in progress so both linuxpatch-*
packages and kernel-patch-* can still be found. kernel-package remains
kernel-package, since it is not specific to Linux (it could, for example, prepare
FreeBSD kernel packages).
The remainder of this section focuses on the 2.6.32 version of the Linux kernel, but the examples
can, of course, be adapted to the particular version of the kernel that you want.
We assume the linux-source-2.6.32 package has been installed. It contains /usr/src/
linux-source-2.6.32.tar.bz2, a compressed archive of the kernel sources. You must extract
these files in a new directory (not directly under /usr/src/, since there is no need for
special permissions to compile a Linux kernel): ~/kernel/ is appropriate.
174 The Debian Administrator's Handbook