{ config, pkgs, ...}:

{

  # ... NixOS usual config ellided ...

  users = {
    mutableUsers = false;

    extraUsers =
      let
        andrehUser =  {
          andreh = {
            # my custom user config
          };
        };
        buildUser = (i:
          {
            "guixbuilder${i}" = {                   # guixbuilder$i
              group = "guixbuild";                  # -g guixbuild
              extraGroups = ["guixbuild"];          # -G guixbuild
              home = "/var/empty";                  # -d /var/empty
              shell = pkgs.nologin;                 # -s `which nologin`
              description = "Guix build user ${i}"; # -c "Guix buid user $i"
              isSystemUser = true;                  # --system
            };
          }
        );
      in
        # merge all users
        pkgs.lib.fold (str: acc: acc // buildUser str)
                      andrehUser
                      # for i in `seq -w 1 10`
                      (map (pkgs.lib.fixedWidthNumber 2) (builtins.genList (n: n+1) 10));

    extraGroups.guixbuild = {
      name = "guixbuild";
    };
  };
}