[franknord23]

I believe this allows you to have cascading restart strategies, similar to what can be done in Erlang/OTP: Only after the StartLimit= has been reached, systemd considers the service as failed. Then services that have Required= set on the failed service will be restarted/marked failed as well.

I think you can even have systemd reboot or move the system into a recovery mode (target) if an essential unit does not come up. That way, you can get pretty robust systems that are highly tolerant to failures.

(Now after reading `man systemd.unit`, i am not fully sure how exactly restarts are cascaded to requiring units.)

[vidarh]

You can trigger units explicitly on failure with OnFailure=someservice as well (and since you can parameterize service names, you can have e.g. a single failure@.service that'll do whatever you prefer once a service fails.

OnFailure makes it easy to implement more complex restart or notification logic.