Systemd can inherit orphaned processes, and there are other ways a service can be running without having a unit file for the given service. I want to know what the catch-all is for services that don't have any service definition when a reboot or halt is issued.
I am specifically interested in signals sent and timeouts, i.e systemd sends all remaining services a sigterm in the order of the lexicographical-sorted service names and after 30 seconds, issues a sigkill to any remaining services. (I don't know if that's correct, but its the type of info I am interested in).
I also would love to know where this is configured and documented.