Linux Unleashed, Third Edition:Using LILO





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The Map Installer
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.
The map installer behavior can be modified by command-line parameters supplied when the installer is invoked or by entries in the configuration file /etc/lilo/config. Many of the options can be given both on the command line and in the configuration file. Before looking at the execution of the map installer and boot examples, we should look at the configuration options.
Map Installer Command-line Syntax
The LILO map installer utility accepts a number of options on the command line. Many of the command-line options are mirrored by configuration variables, discussed in the next section. Allowed options are shown in Table 4.2.

Table 4.2.Options that the map installer allows.



Option
Meaning



b dev
Uses dev as the boot device. If no value is specified, the default device given by the boot configuration variable is used.

c
Turns compact on, merging read requests for adjacent sectors into one request to reduce load time. Often used for boot floppies. The compact configuration variable can also be used to specify this option.

C file
Uses file as the configuration file. If no file is specified, /etc/lilo/config is used as the default.

d secs
The number of tenths of seconds to wait before booting the first image. Also can be specified in the configuration variable delay.

f file
Uses file as the name of the disk parameter table (called disktab). If a filename is omitted, the file /etc/lilo/disktab is used.

i sector
Installs the kernel as the new boot sector. Can be read from the install configuration variable.

I name
Displays the path of the name kernel image file. If no matching name is found, an error is generated. The option “v” can be added after the name to verify the existence of the image file. This option uses the BOOT_IMAGE environment variable.

l
Generates linear sector addresses instead of the default sector/head/cylinder addresses. Can also be specified with the configuration variable linear.

m file
Uses file as the location of the map file. If no filename is given, /etc/lilo/map is used.

P fix
Allows LILO to adjust sector/head/cylinder addresses using the table file. Also specified with the fix table configuration variable.

P ignore
Overrides correction of sector/head/cylinder addresses. Also specified with the ignore table configuration variable.

q
Displays the currently mapped files.

r dir
Performs a chroot command on dir before continuing. This is necessary if the root file system is mounted in a different location from the map installer command. Because the current directory is changed with this command, use absolute pathnames for all files.

R words
Stores words in the map file for use by the boot loader. The words are parameters used by the boot process as part of the default command line. The first word must be the name of the boot image.

s file
Copies the original boot sector to file instead of /etc/lilo/ boot.hex_num.

S file
Same as s but overwrites the old file if it exists.

t
Performs a test by executing the entire installation process except writing the map file and boot sector. Ideally used with the v option to verify accurate behavior of the map installer.

u dev
Restores the backup copy of the boot sector for dev. If no device is specified, the default value is used or, failing a valid value, the current root device. The backup copy is checked for a time stamp before the write is completed.

U dev
Same as u except no check for the time stamp.

v level
Uses the verbose output level specified to display messages.

V
Displays the version number of the map installer, then exits.







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