@KarstenV Hello again. That looks like quite a find. Also the batteries are pretty standard by the looks of it so if they are nearly shot it shouldn’t be too expensive to replace them.
Yes the user feedback / telemetry is definitely a weak area currently in the NUT/UPS side. I’m hoping that we get a widget or the like in time but the initial priority was just to get the setup interface done. I tried to squeeze a basic monitor in there but there just wan’t time.
Yes I’m afraid, somewhat sadly, that is the only current feedback of success!
Anyway, to your question.
The command you are looking for is something along the lines of:
upsc ups@localhost
assuming you have the ups locally connected then the Rockstor setup defaults to using the “ups” name.
I thought I’d put this in the developer docs on this feature (Network UPS Tools (NUT) - Rockstor's implementation) but apparently not (on just looking).
You might like to look at the final section “Some shiny” of my Rockstor blog post “Why NUT” on ways you can monitor the UPS over the network from any number of machines. I use the Gnome Shell Extension walNUT. You would have to run the Rockstor NUT instance in netserver mode rather than standalone though. Details of how to configure in all the various modes is available in our UPS / NUT Setup official docs section.
And given the output power of that model 1200W (2000VA) you might be able to use it for more than just the Rockstor machine. NUT can also facilitate the shutting down of client machines via it’s network client server model. Again if the UPS is attached directly to the Rockstor instance (data cable wise) it would have to run in netserver mode while the other machines in netclient mode, just remember to power the ethernet switch from the UPS as well though 
. It takes pains to attempt to shut the client machines down first as well which is nice.
Hope that helps.