NixOS is a Linux distribution with a unique approach to package and configuration management. Built on top of the Nix package manager, it is completely declarative, makes upgrading systems reliable, and has many other advantages.
NixOS has a completely declarative approach to configuration management: you write a specification of the desired configuration of your system in NixOS’s modular language, and NixOS takes care of making it happen.
NixOS has atomic upgrades and rollbacks. It’s always safe to try an upgrade or configuration change: if things go wrong, you can always roll back to the previous configuration.
Declarative specs and safe upgrades make NixOS a great system for DevOps use. NixOps, the NixOS cloud deployment tool, allows you to provision and manage networks of NixOS machines in environments like Amazon EC2 and VirtualBox.