{ lib
, pkgs
}:

# assumes nspawn-tarball.nix is mixed into it
nixosConfiguration:

let

  hostname = nixosConfiguration.config.networking.hostName;

  setup = pkgs.substituteAll {
    src = ./setup-nspawn.sh;
    isExecutable = true;
    inherit hostname;
  };

  inherit (nixosConfiguration.config.system.build) tarball;

in

pkgs.runCommandNoCC "nspawn-setup-${hostname}.sh" {
  nativeBuildInputs = with pkgs; [ makeself ];
} ''
  mkdir -p archive/
  ln -s ${setup}     archive/setup.sh
  ln -s ${tarball}/* archive/nixos-${hostname}.tar
  makeself --follow archive/ $out setup-nixos-nspawn-${hostname} ./setup.sh
''