NixOS is a Linux distribution built around the Nix package manager. Unlike traditional Linux distributions, NixOS is configured using Nix's functional programming language or one of Nix's forks. The operating system builds itself according to declarations written by the user within its config files, allowing them to manage and alter all aspects of their system, as well as install identical builds of that system on any other machine. From those files, NixOS generates complete system profiles, enabling reproducible deployments, atomic upgrades, and system rollbacks. Representing the primary implementation of the Nix package manager, NixOS is often just referred to eponymously as Nix.