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Chapter 4. Boot Loaders

This file would tell GRUB to build a menu with Red Hat Linux as the default operating system, set

to autoboot it after 10 seconds. Two sections are given, one for each operating system entry, with

commands specific to this system's disk partition table.

Note

Note the default is specified as a number. This refers to the first title line GRUB comes across. If

you want windows to be the default, change the default= value to 1.

Configuring a GRUB menu configuration file to boot multiple operating systems is beyond the scope

of this chapter. Please consult Section 4.11 for detailed information about configuring GRUB to boot

different operating systems.

4.8. 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.

4.8.1. 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 Section 3.2.

LILO loads itself into memory almost identically to GRUB, except it is only a two stage loader.

1. The Stage 1 or primary boot loader is read into memory by the BIOS from the MBR

2

. 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.

2. 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.

3. 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.

2. For more on the system BIOS and the MBR, see Section 3.2.1.