NixOS

A Linux distribution built on a purely functional package manager to ensure reproducible, atomic, and declarative system configurations.

NixOS treats the entire operating system as a function of your configuration file (usually configuration.nix). By leveraging the Nix package manager, it stores every package version in a unique path within /nix/store, preventing dependency conflicts and enabling instant rollbacks if a change fails. You define your users, services, and kernel parameters in one place: the system builds to match that specification exactly. This approach eliminates the 'it works on my machine' problem across your fleet, whether you are managing a single ThinkPad or a thousand production nodes.

https://nixos.org