Textbook of Linux

Debian is one of the oldest and most influential Linux distributions, founded by Ian Murdock in 1993. The name combines "Debra" (his then-girlfriend) and "Ian". Debian is entirely community-driven, with no corporate owner, and is governed by its project members via elected leaders and a formal constitution. Its guiding document, the Debian Social Contract, commits to producing a 100% free operating system and to prioritising the free-software community.

Debian ships in three main branches: stable (the current release, with security updates for years), testing (the next release in preparation), and unstable (where new packages land first; code-named "sid"). A stable release is supported for about five years and is famous for being boring in the best sense: it does not break.

Debian is the base of an enormous derivative tree: Ubuntu (and all its flavours and forks), Linux Mint, Kali Linux, Raspberry Pi OS, Tails, Proxmox, Devuan (Debian without systemd), and many more. Its package manager apt and its .deb format are used across all of them.

For servers where stability is paramount, Debian is a classic choice. For desktops, its derivatives (particularly Ubuntu and Mint) are more common, because they bundle friendlier defaults and proprietary firmware that Debian proper keeps at arm's length.