86

Chapter 4. Boot Loaders

label=linux

initrd=/boot/initrd 2.4.0 0.43.6.img

read only

root=/dev/hda5

other=/dev/hda1

label=dos

This example shows a system configured to boot two operating systems: Red Hat Linux and DOS.

Here is a deeper look at a few of the lines of this file:

  boot=/dev/hda

tells LILO to install itself on the first hard disk on the first IDE controller.

  map=/boot/map

locates the map file. In normal use, this should not be modified.

  install=/boot/boot.b

tells LILO to install the specified file as the new boot sector. In normal

use, this should not be altered. If the

install

line is missing, LILO will assume a default of

/boot/boot.b

as the file to be used.

The existence of

prompt

tells LILO to show you whatever is referenced in the

message

line. While

it is not recommended that you remove the

prompt

line, if you do remove it, you can still get a

prompt by holding down the [Shift] key while your machine starts to boot.

  timeout=50

sets the amount of time that LILO will wait for user input before proceeding with

booting the

default

line entry. This is measured in tenths of a second, with 50 as the default.

  message=/boot/message

refers to the screen that LILO displays to let you select the operating

system or kernel to boot.

  lba32

describes the hard disk geometry to LILO. Another common entry here is

linear

. You

should not change this line unless you are very aware of what you are doing. Otherwise, you could

put your system in an unbootable state.

  default=linux

refers to the default operating system for LILO to boot from the options listed

below this line. The name

linux

refers to the

label

line below in each of the boot options.

  image=/boot/vmlinuz 2.4.0 0.43.6

specifies the linux kernel to boot with this particular

boot option.

  label=linux

names the operating system option in the LILO screen. In this case, it is also the

name referred to by the

default

line.

  initrd=/boot/initrd 2.4.0 0.43.6.img

refers to the initial ram disk image that is used at

boot time to actually initialize and start the devices that makes booting the kernel possible. The

initial ram disk is a collection of machine specific drivers necessary to operate a SCSI card, hard

drive, or any other device needed to load the kernel. You should never try to share initial ram disks

between machines.

read only

specifies that the root partition (see the

root

line below) is read only and cannot be

altered during the boot process.

  root=/dev/hda5

tells LILO what disk partition to use as the root partition.

4.10. Changing Runlevels at Boot Time

Under Red Hat Linux, it is possible to change your default runlevel at boot time.

If you use LILO as your boot loader, access the

boot:

prompt by typing [Ctrl] [X]. Then type:

linux number