I have not found a way for systemd to recognize that some required non-systemd process is required to be running before I start mine. In Upstart I could do, for example,
if pgrep -f bin/postgres
The closest I've found is "path based activation", which would let me look for a lock file, but this is clunky and not guaranteed since sometimes lock files get orphaned.
I do not want to rewrite all the processes that are not using systemd so that they now do use it - I just want to start one particular process that way.
Is there no such option, or have I just not found it?