Modifying the Bootloader For the New Kernel
There are two common Linux kernel bootloaders: GRUB and LILO. GRUB
is the one more commonly used
in modern distributions, and does some things a little more easily than
LILO, but LILO is still seen as well. We'll cover both in this section.
To determine which bootloader your system uses, look in the
/boot/ directory. If there is a
grub subdirectory:
$
ls -F /boot | grep grub
grub/
then you are using the GRUB program to boot with. If
this directory is not present, look for the presence of the
/etc/lilo.conf file:
$
ls /etc/lilo.conf
/etc/lilo.conf
If this is present, you are using the LILO program
to boot with.
The steps involved in adding a new kernel to each of these programs are
different, so follow only the section that corrisponds to the program you
are using.
To let GRUB know that a new kernel is present, all you need
to do is modify the /boot/grub/menu.lst file.
For full details on the structure of this file, and all of the different
options available, please see the GRUB info pages:
$
info grub
The easiest way to add a new kernel entry to the
/boot/grub/menu.lst file is to copy an existing
entry. For example, consider the following menu.lst
file from a Gentoo system:
timeout 300
default 0
splashimage=(hd0,0)/grub/splash.xpm.gz
title 2.6.16.11
root (hd0,0)
kernel /bzImage-2.6.16.11 root=/dev/sda2 vga=0x0305
title 2.6.16
root (hd0,0)
kernel /bzImage-2.6.16 root=/dev/sda2 vga=0x0305
The line starting with the word title defines a new
kernel entry, so this file contains two entries. Simply copy the lines from one instance of the
title word to the next one, such as :
title 2.6.16.11
root (hd0,0)
kernel /bzImage-2.6.16.11 root=/dev/sda2 vga=0x0305
to the end of the file, and edit the version number to contain the version
number of the new kernel you just installed.
The title does not matter, so long as it is unique, but it is
displayed in the boot menu, so you should make it something meaningful. In our example, we installed
the 2.6.17.11 kernel, so the final copy of the file
looks like:
timeout 300
default 0
splashimage=(hd0,0)/grub/splash.xpm.gz
title 2.6.16.11
root (hd0,0)
kernel /bzImage-2.6.16.11 root=/dev/sda2 vga=0x0305
title 2.6.16
root (hd0,0)
kernel /bzImage-2.6.16 root=/dev/sda2 vga=0x0305
title 2.6.17.11
root (hd0,0)
kernel /bzImage-2.6.17.11 root=/dev/sda2 vga=0x0305
After you save the file, reboot the system and ensure that the new
kernel image's title comes up in the boot menu. Use the down arrow to
highlight the new kernel version, and press Enter to
boot the new kernel image.
To let LILO know that a new kernel is present, you must modify the
/etc/lilo.conf configuration file and then run the
lilo
command to apply the changes made to
the configuration file. For full details on the structure of the
LILO configuration file, please see the
LILO man page:
$
man lilo
The easiest way to add a new kernel entry to the
/etc/lilo.conf file is to copy an existing
entry. For example, consider the following LILO
configuration file from a Gentoo system:
boot=/dev/hda
prompt
timeout=50
default=2.6.12
image=/boot/bzImage-2.6.15
label=2.6.15
read-only
root=/dev/hda2
image=/boot/bzImage-2.6.12
label=2.6.12
read-only
root=/dev/hda2
The line starting with the word image= defines a new
kernel entry, so this file contains two entries. Simply copy the lines from one instance of the
image= word to the next one, such as:
image=/boot/bzImage-2.6.15
label=2.6.15
read-only
root=/dev/hda2
to the end of the file, and edit the version number to contain the version
number of the new kernel you just installed. The label does not matter, so long as it is unique, but it is
displayed in the boot menu, so you should make it something meaningful. In our example, we installed
the 2.6.17.11 kernel, so the final copy of the file
looks like:
boot=/dev/hda
prompt
timeout=50
default=2.6.12
image=/boot/bzImage-2.6.15
label=2.6.15
read-only
root=/dev/hda2
image=/boot/bzImage-2.6.12
label=2.6.12
read-only
root=/dev/hda2
image=/boot/bzImage-2.6.17
label=2.6.17
read-only
root=/dev/hda2
After you save the file, run the /sbin/lilo program
to write the configuration changes out to the boot section of
the disk:
# /sbin/lilo
Now the system can be safely rebooted. The new kernel choice can be seen
in the list of kernels that are available at boot time. Use the down arrow
to highlight the new kernel version, and press Enter to
boot the new kernel image.
