Arch Linux
Arch Linux is an independently developed, x86_64-optimised Linux distribution targeted at competent Linux users. It uses 'pacman', its home-grown package manager, to provide updates to the latest software applications with full dependency tracking.
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NixOS
NixOS is an independently developed GNU/Linux distribution that aims to improve the state of the art in system configuration management. In NixOS, the entire operating system, including the kernel, applications, system packages and configuration files, are built by the Nix package manager.