buildInputs = with pkgs; [

  packages = with pkgs; [

          # created = "now";

            # This is a very simple overlay, but in general they can be used to manipulate nixpkgs,
            # e.g. to change some piece of software to a different version, or add a patch, or... the sky is the limit.

      # Having the container be created 'now' can be convenient to identify
      # different versions of containers, but it breaks reproducibility.
      # So we let Nix set it to a fixed timestamp 0.

      buildInputs = with pkgs; [

      # Packages available in the development shell
      packages = with pkgs; [