> like "at least one real IP address is available" or "time has been synced"

"network-online.target is a target that actively waits until the network is “up”, where the definition of “up” is defined by the network management software. Usually it indicates a configured, routable IP address of some kind. Its primary purpose is to actively delay activation of services until the network has been set up."

For time sync checks, I assume one of the targets available will effectively mean a time sync has happened. Or you can do something with ExecStartPre. You could run a shell command that checks for the most recent time sync or forces one.

it's the "usually" that's the problem

this service (untouched by me) had:

After=local-fs.target network-online.target remote-fs.target time-sync.target

but it was still started without an IP address, and then failed to bind

just like this sort of problem: https://github.com/systemd/systemd/issues/4880#issuecomment-...

the entire thing is unreliable and doesn't act like you'd expect

> Or you can do something with ExecStartPre. You could run a shell command that checks for the most recent time sync or forces one.

at that point I might as well go back to init=/etc/rc

Is it possible for network-online to mean that, or does network-on actually mean that?

It is possible for a specification to be so abstract that it's useless.