LPIC 102

Compiling a kernel 1 Aim

We aim to be able to compile a Linux kernel.

2

Background

In this laboratory the old DEC network cards use a driver that is included in the kernel source code, but it is not built in the default setup that we use in this laboratory. We need this built as a module that can be loaded into the kernel so that we can use the network card. There are a number of steps in the process: • We verify that the kernel source code is installed. • I prefer to build the kernel not as root, but as a normal user. We will change the ownership of the kernel source code to our own account. • We edit the Makeﬁle and change the EXTRAVERSION name near the top so that the kernel will have a diﬀerent name from the kernel provided by the distribution. • We copy a suitable conﬁguration ﬁle from those provided by the distribution, or we can go through and choose the details of conﬁguration ourselves, though this is quite time consuming, as there are many conﬁguration options to choose. The name of the conﬁguration ﬁle is .config • We start a conﬁguration program that provides a graphical user interface that edits the conﬁguration ﬁle with make xconfig • We calculate the dependencies (which things need to be compiled) with make dep. • We build the kernel with make bzImage • We build the modules with make modules • We install the modules with sudo make modules install • We copy the kernel to the /boot directory • We also copy the System.map ﬁle and the .config ﬁles to the /boot directory. • Generate a ram disk ﬁle with mkinitrd. • We edit the GRUB conﬁguration so we can boot our new kernel. • We boot into our new kernel and watch with a happy smile as everything works.
Nick Urbanik nicku(at)nicku.org ver. 1.0

Compiling a kernel LPIC 102

2

3
3.1

Procedure
Change the Ownership of the Source Code
1. Notice the dot ‘.’ at the end of the chown command. Use your own username instead of jimmy. $ cd /usr/src ← $ ls ← debug linux-2.4 linux-2.4.21-15.EL $ cd linux-2.4.21-15.EL ← $ chown -R jimmy.jimmy . ←

redhat

We will call the current location the top level of the source directory. 2. Let us clean up any other residue from previous compiles with $ make clean ←

3.2

Change the Name of the Kernel: Edit the Makefile

1. With the editor of your choice (emacs, gedit, vi, nano. . . , edit the ﬁle Makefile in the top level directory, and 2. change the line EXTRAVERSION = -15.EL to EXTRAVERSION = -15.ELde4x5

3.3

Get a Conﬁguration File

1. Red Hat provide some conﬁguration ﬁles in the config directory. Get an appropriate conﬁguration for the computer and. . . $ cd configs ← $ ls ← kernel-2.4.21-athlon.config kernel-2.4.21-ia32e.config kernel-2.4.21-athlon-smp.config kernel-2.4.21-ia64.config kernel-2.4.21-i386-BOOT.config kernel-2.4.21-ppc64.config kernel-2.4.21-i386.config kernel-2.4.21-ppc64iseries.config kernel-2.4.21-i586.config kernel-2.4.21-ppc64pseries.config kernel-2.4.21-i586-smp.config kernel-2.4.21-s390.config kernel-2.4.21-i686.config kernel-2.4.21-s390x.config kernel-2.4.21-i686-hugemem.config kernel-2.4.21-x86_64.config kernel-2.4.21-i686-smp.config kernel-2.4.21-x86_64-smp.config $ cp kernel-2.4.21-i686.config ../.config ← . . . copy it to the name .config in the top level. 2. Have a look at the conﬁguration ﬁle with less or your editor.
Nick Urbanik nicku(at)nicku.org ver. 1.0

Compiling a kernel LPIC 102

3

3.4

Edit the Conﬁguration with make xconfig
$ make xconfig ← This will start a Tk program that allows you to select conﬁguration options.

1. In the top level directory, type:

2. Choose the menu item Network Interfaces 3. Find the item that corresponds the the de4x5 module, and select m for module You can click on the help buttons to ﬁnd what each conﬁguration option is for. 4. Save the conﬁguration and exit the program.

3.5

Make the Dependencies

$ make dep ←

3.6

Build the Kernel

$ make bzImage ←

3.7

Build the Modules

$ make modules ←

3.8

Install the Modules

$ sudo make modules install ←

3.9

Copy the kernel to /boot

$ sudo cp -a arch/i386/boot/bzImage /boot/vmlinuz-2.4.21-15.ELde4x5 ← $ sudo cp -a System.Map /boot/System.map-2.4.21-15.ELde4x5 ← $ sudo cp -a .config /boot/config-2.4.21-15.ELde4x5 ←

3.10

Make an RAM disk ﬁle with mkinitrd

$ cd /boot ← $ /sbin/mkinitrd -v initrd-2.4.21-15.ELde4x5.img 2.4.21-15.ELde4x5 ←

3.11

Edit GRUB Conﬁguration to Boot the New Kernel

1. Edit /boot/grub/grub.conf (or /boot/grub/menu.lst) and copy the section for booting the old kernel 2. Edit it, changing the name of the kernel and initrd ﬁle to match what you have made 3. Boot the computer into your new kernel and rejoice!

Nick Urbanik nicku(at)nicku.org

ver. 1.0