Write and Enable a systemd Service

/opt/relay/bin/relay is a daemon that has been started by hand. This server image is built offline, so systemd is not running yet. Prepare the service the way it will run in production.

Task

Create the unit /etc/systemd/system/relay.service so that:

• it runs /opt/relay/bin/relay --config /etc/relay.conf
• it runs as user relay and group relay
• it starts only after the network is online (network-online.target), and wants that target
• it restarts on failure, waiting 5 seconds between attempts
• it has a Description mentioning relay

Then enable it for the normal multi-user boot, exactly as systemctl enable would.