The map installer is the program that updates the boot sector and creates the map file. The map installer is usually the file /etc/lilo/lilo. Whenever the map installer is running, it checks for errors in the boot sector. If an error is detected, no changes to the boot sector are written, and the installer terminates.

When a boot sector is successfully updated by the map installer, the old boot sector contents are copied into the directory /etc/lilo with the name boot.hex_num where hex_num is the hexadecimal device number of the partition that was rewritten. The hexadecimal device numbers were mentioned in the previous section. When the map installer writes to a partition’s boot sector, the old copy of the boot sector is stored in a file with the name part.hex_num. Again, hex_num is the number of the device.

You can modify the map installer’s behavior by supplying command line parameters when the installer is invoked or by making entries in the configuration file /etc/lilo/config. On later versions of Linux, including the version supplied on the CD-ROM with this book, the file is /etc/lilo.conf. A sample /etc/lilo.conf looks like the following:

# LILO configuration file

# generated by ‘liloconfig’

#

# Start LILO global section

boot = /dev/fd0

#compact # faster, but won’t work on all systems.

delay = 50

vga = normal # force sane state

ramdisk = 0 # paranoia setting

# End LILO global section

# Linux bootable partition config begins

image = /vmlinuz

root = /dev/sda3

label = Linux

read-only # Non-UMSDOS filesystems should be mounted read-only for checking

# Linux bootable partition config ends

# DOS bootable partition config begins

other = /dev/sda1

label = DOS

table = /dev/sda

# DOS bootable partition config ends

As you can see, this lilo.conf file uses a boot floppy disk to hold the LILO image (/dev/fd0) and avoids overwriting the MBR or superblock of a partition. The Linux partition is /dev/sda3 and is called Linux. A DOS partition, /dev/sda1, called DOS also exists on the hard drive. You can use many of the available options from either the LILO command line or the configuration file. The following sections discuss the configuration options.