The LILO is a small utility designed to load the Linux kernel (or the boot sector of another operating system) into memory and start it. A program that performs this function is commonly called a boot loader. LILO consists of two parts:

The boot loader

This is a two-stage program intended to find and load a kernel. It’s a two-stage operation because the boot sector of the disk is too small to hold the entire boot loader program. The code located in the boot sector is compact because its only function is to launch the second stage, which is the interactive portion. The first stage resides in the MBR or first boot partition of the hard disk. This is the code that is started at boot time by the system BIOS. It locates and launches a second, larger stage of the boot loader that resides elsewhere on disk. The second stage offers a user prompt to allow boot-time and kernel image selection options, finds the kernel, loads it into memory, and launches it.

The lilo command

Also called the map installer, the lilo command is used to install and configure the LILO boot loader. The command reads a configuration file that describes where to find kernel images, video information, the default boot disk, and so on. It encodes this information along with physical disk information and writes it in files for use by the boot loader.

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