[Unit]
     Description=runs only upon shutdown
     DefaultDependencies=no
     Conflicts=reboot.target
     Before=shutdown.target
     Requires=poweroff.target
     After=network.target

     [Service]
     Type=oneshot
     ExecStart=/bin/true
     ExecStop=/bin/bash /usr/local/bin/shutdown_screen
     RemainAfterExit=yes

     [Install]
     WantedBy=multi-user.target