Is there any systemd equivalent to "initctl emit"? In `upstart`, it was possible to send custom events with `initctl emit custom-event`. It was also possible to use these custom events on the `start on` and `stop on` stanzas. Does systemd provides something similar to this? There is no mention of it on the SystemdForUpstartUsers page of Ubuntu wiki.

No. This is one of the fundamental differences between `upstart` and `systemd`. `upstart` is event-based, one of the novel design features that was touted when it was introduced. `systemd` is not event-based.

You'll have to work out what you are using `initctl emit` _for_ , and determine how to achieve that in the different `systemd` model.