NixOS is a Linux distribution whose first version was released in 2013. It is different from Nix, the package manager on which it is based. When applied to the entire system, Nix's purely functional deployment model makes NixOS stand out from other distributions. Among its strengths:

• System reproducibility: NixOS is based on a declarative model. The entire OS is built by Nix from configuration files (the main one is configuration.nix, located in /etc/nixos/). The configuration can be modified and rebuilt at any time using the nixos-rebuild switch command. This makes NixOS easily reproducible. It allows you to get the desired configuration files on the target machine and to launch a build on this machine.
• Atomic and reliable updates and rollback system: Each build is kept in memory which allows to come back to any previous version. In case of interruption during a build, a power failure for example, the system restarts autonomously on the previous version.
• Package management: Nix manages packages in an isolated way. It allows different versions of the same dependency to coexist on the same device. This management is also facilitated and optimized between several users.