Module Release May 2003: Booting

This month's offering concentrates on the basics of booting a Linux system.

LPI 101 objective 2.6.1 asks you to:

Guide the system through the booting process, including giving options to the kernel at boot time, and check the events in the log files.

The module begins by introducing the concept of a boot loader and explaining its rôle in booting the system. In essence, a boot loader specifies where to find an operating system kernel, loads it into memory, then passes parameters (options) to it, e.g., giving the kernel particular hardware options to use. Most people use a bootloader to run different Linux configurations or multiple operating systems (i.e., dual booting).

For a long time LILO (the LInux LOader) has been the default boot loader on Linux systems. Most distributions offer alternatives, and several (including Redhat) use the somewhat more complex Grub boot loader as their default. This module only deals with LILO, because it is both the most widespread boot loader and because it is specified for the Linux Professional Institute (LPI) 101 exam.

A suitable level of detail is provided on how to edit the configuration file /etc/lilo.conf to select different OS kernels and to pass particular parameters to them. In addition to explaining the general syntax and meaning of the configuration file, the module also identifies and explains a few of the most common kernel parameters that people might want to use.

Towards the end of the module details are provided on how to use the dmesg command and the file /var/log/dmesg to access the useful diagnostic messages that the kernel generates as it starts up. Finally, a small amount of information is provided about how to identify, load and unload kernel modules.