LILO

LILO, short for Linux Loader, is a boot loader used to start Linux on x86 systems. It was one of the early, widely deployed boot managers and served as the default bootloader for many distributions in the 1990s and early 2000s. LILO’s primary function is to load the Linux kernel into memory and begin executing it; it can also boot other operating systems if configured to do so.

LILO works in a two-stage process. A small first stage is stored in the Master Boot Record or in a partition boot sector, which then loads a second stage from disk. The second stage reads the kernel image and optional initial RAM disk as specified in its configuration. The boot configuration is kept in a plain text file, typically /etc/lilo.conf, where kernel images are declared with image stanzas and optional entries for other operating systems. Boot parameters such as the default entry, timeout, and kernel arguments (append=) can be set in this file. An administrator installs or updates LILO with the lilo command, which writes boot code to the chosen boot sector or MBR and uses the current configuration.

LILO has several limitations by modern standards. It requires manual configuration and reinstallation after kernel updates, as changes are not detected automatically. It provides fewer features than newer bootloaders, such as dynamic OS detection and graphical menus. Its reliance on static disk geometry and explicit paths can make maintenance brittle on changing hardware.

Today, LILO remains available for legacy systems but has largely been superseded by GRUB and other boot managers. It can still perform simple dual-boot setups when correctly configured, though migration to a newer bootloader is common practice.