nixos/tzupdate: use timedatectl to actually set the timezone

      description = "tzupdate timezone update service";

      wants = [ "network-online.target" ];

      after = [ "network-online.target" ];

      script = ''

        timedatectl set-timezone $(${lib.getExe pkgs.tzupdate} --print-only)

      '';

      serviceConfig = {

        Type = "oneshot";

        # We could link directly into pkgs.tzdata, but at least timedatectl seems

        # to expect the symlink to point directly to a file in etc.

        # Setting the "debian timezone file" to point at /dev/null stops it doing anything.

        ExecStart = "${pkgs.tzupdate}/bin/tzupdate -z /etc/zoneinfo -d /dev/null";

      };

    };

  };