systemd-suspend.service man page:
Note that scripts or binaries dropped in /lib/systemd/system-sleep/ are intended for local use only and should be considered hacks. If applications want to be notified of system suspend/hibernation and resume, there are much nicer interfaces available.
So what are some of these "nicer interfaces" that I can use to get notified before suspension? (would be nice if it is before n sec/min)
"Nicer interfaces" is probably referring to the Inhibitor Locks implemented in systemd-logind.service, which includes a logic to inhibit system shutdowns and sleep states.
From man systemd-logind.service:
DESCRIPTION
systemd-logind is a system service that manages user logins. It is responsible for:
- ...
- Implementing a shutdown/sleep inhibition logic for applications
...
For more information on the inhibition logic see the Inhibitor Lock Developer Documentation.
Another solution that I can think of is to write a systemd service, see https://www.freedesktop.org/software/systemd/man/systemd.unit.html and this related question for example.
