This is my NixOS configuration. I use it to manage:

• some vps serving some websites and services (misskey, synapse), etc.
• my laptop (Lenovo R9000P 2023), and my tablet (One Netbook One Mix 4).
• some cluster for scientific computing (vasp, lammps, etc). With the following highlights:
• All binary is compiled for specific CPU (-march=xxx, like that on Gentoo).
• All packages and configurations are managed by Nix, as much reproducible as possible.

Using overlay

An overlay is provided through outputs.overlays.default, you could use it in your configuration.nix like this:

{
  inputs.chn-nixos.url = "github:CHN-beta/nixos";
  outputs.nixosConfigurations.my-host = inputs.nixpkgs.lib.nixosSystem
  {
    modules = [({pkgs, ...}: { config =
    {
      nixpkgs.overlays = [ inputs.chn-nixos.overlays.default ];
      environment.systemPackages = [ pkgs.localPackages.vasp.intel ];
    };})];
  };
}