I'm still confused. What is Nix? Is it an OS, or a package manager? From the looks of it it's a package manager that I should be able to use it on any POSIX system, but I doubt that's the case?

What is Nix?

Nix is a powerful package manager for Linux and other Unix systems that makes package management reliable and reproducible. It provides atomic upgrades and rollbacks, side-by-side installation of multiple versions of a package, multi-user package management and easy setup of build environments.

What is NixOS?

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.

[1]: https://nixos.org/

mehrdadn

Thanks, but that makes me wonder how that's even possible given that distros make their own modifications? Do people port each distro's packages to Nix then? Are they kept up-to-date? Or does it automatically translate from apt/pacman/etc. databases somehow? Or does it just basically install vanilla packages on all distro?

throwaway894345

Yeah, there is a giant repo of package definitions at https://github.com/NixOS/nixpkgs. Those definitions tell nix how to build everything from the ground up.