Man I miss cron. I've had a tough time in the past getting systemd boot scripts to run at precisely the right time at boot, but now I'm at a total loss with timers.
This should be simple. I'm trying to get a .sh file to run on a timer at boot. The forum postings on timers across multiple boards are inconsistent, and Raspbian seems to have its own quirks about where you [Install] your service/timer that vary from other distributions. Moreover if I run the timer by hand it works... but when I reboot it does nothing. There doesn't seem to be a good step-by-step tutorial anywhere for how to create and install a timer on boot on ANY distribution, and the fact that the .service and .timer files work properly when manually started makes me all the more frustrated. It has to be something simple that I'm not doing.
So my question is just that. Can someone walk me through every step - not skipping a line - for how to run /usr/pi/foo.sh every 120 seconds after boot? I could post the 25 different things I've tried so far, but for such an easy task I figure this would be the easiest way of asking. For the purposes of this script, the launch timing doesn't matter - but close to the end of boot or after boot is ideal.
Thank you for your help.