Fedora
Fedora Linux (formerly Fedora, formerly Fedora Core) is a Linux distribution developed by the community-supported Fedora Project and owned by Red Hat. Fedora Linux contains software distributed under a free and open-source license and aims to be on the leading edge of such technologies.
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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.