LILO
LILO is an acronym for LInux
LOader and has been used to boot Linux on x86
systems for many years. Although GRUB is now the default boot loader,
some prefer to use LILO because it is more familiar to them and others
use it out of necessity, since GRUB may have trouble booting some
hardware.
LILO and the x86 Boot Process
This section will discuss in more detail the specific role LILO plays
when booting an x86 system. For a detailed look at the overall boot
process, see the Section called A Detailed Look at the Boot Process in Chapter 3.
LILO loads itself into memory almost identically to GRUB, except it is
only a two stage loader.
The Stage 1 or primary boot loader is read into
memory by the BIOS from the MBR[1]. The primary boot loader exists on less
than 512 bytes of disk space within the MBR. The only thing it
does is load the Stage 2 boot loader and pass to it disk
geometry information.
The Stage 2 or secondary boot loader is read into
memory. The secondary boot loader displays the Red Hat Linux
initial screen. This screen allows you to select which operating
system or Linux kernel to boot.
The Stage 2 boot loader reads the operating system
or kernel and initrd into
memory. Once LILO determines which operating system
to start, it loads it into memory and hands control of the
machine to that operating system.
Once the Stage 2 boot loader is in memory, LILO displays the initial
Red Hat Linux screen with the different operating systems or kernels it has
been configured to boot. If you only have Red Hat Linux installed and have not
changed anything in LILO's configuration file, you will see only
linux as an option. If you install SMP
kernel support, you will see linux-up as an
option. If you have set up LILO to boot other operating systems as
well, this screen is your chance to select what operating system will
boot. Use your arrow keys to highlight the operating system and press
[Enter]
If you would like to have a command prompt to enter a command to LILO,
press
[Ctrl]-[X]. LILO
displays a LILO: prompt on the screen and waits for
input from the user.
LILO vs. GRUB
In general, LILO works similarly to GRUB except for three major
differences:
It has no interactive command interface.
It stores information about the location of the kernel or other
operating system it is to load on the MBR.
It cannot read ext2 partitions.
The first point means the command prompt for LILO is not interactive and
only allows one command with arguments.
The last two points mean that if you change LILO's configuration file
or install a new kernel, you must rewrite the Stage 1 LILO boot loader
to the MBR by issuing the /sbin/lilo -v -v
command. This is more risky than GRUB's method, because a
misconfigured MBR leaves the system unbootable. With GRUB, if the
configuration file is erroneously configured, it will simply default
to its command line interface.
 | Tip |
|---|
| | If you upgrade the kernel using the Red Hat Update
Agent, the MBR will be updated automatically. For more
information on RHN, refer to the following URL, https://rhn.redhat.com
|
