Write PID file when starting server as daemon

[t-erxleben]

A PID file would be nice to have when starting the server as daemon. This would be useful for writing a systemd unit (or whatever init system).

[michaelkuhn]

If we start the server as part of a systemd service, couldn't we simply use the foreground mode (without --daemon), so systemd can determine its PID?

The systemd man page actually states:

Note that PID files should be avoided in modern projects. Use Type=notify or Type=simple where possible, which does not require use of PID files to determine the main process of a service and avoids needless forking.