Controls when systemd restarts the service after it exits. This writes Restart=.

no disables automatic restarts. on-failure restarts after non-zero exits, signals, timeouts, and watchdog failures. always restarts after almost any exit except an explicit stop by systemd.

on-success, on-abnormal, on-abort, and on-watchdog are narrower policies. For ordinary server processes, on-failure is usually the practical choice.