Powering Rasberry PI off

I have two UPS batteries, one driving my Allonis and Home Automation computers, and the other driving my main computer and network stuff. The main computer's UPS was getting old, so I just replaced it, and splurged on a more expensive one that allows power monitoring by a NUT server. The logic I have is that when the main computer detects that power is still out after a couple of minutes, it will send commands to Allonis and the HA computer to shut down (I don't need either one to be running if the power is out). I want to save the batteries on both UPS's in case of an extended blackout (the UPS's are then ready to recharge phones or run lights).

I am using a HTTP get command to turn off Allonis ( 192.168.0.nn/api/docommand?command=poweroff ). Unfortunatly it only shuts down the processer, not the entire Rasberry PI. Which also means that pushing the "on" button does not restart the Rasberry. It seems that the Rasberry still needs to be actually power cycled to get it to completely shut off, and also to allow it to turn back on. My google searches indciate that is the way Rasberry's seem to work. So the question becomes is there a wasy to get the Rasberry PI to completely shut down?

The purpose of the shut down is to completely stop any power drain on the UPS. I could put a smart plug on the Allonis Rasberry, but that smart plug would probably have an drain somewhat equal to the level of an idle Allonis Rasberry.

Not quite following what you are trying to do...but here is how we implement UPS allonis.com/support/documentation?view=category&id=433

My Allonis system's UPS is a less expensive one that does not have monitoring capability. The Allonis UPS driver will not work for me because of this (unless the Allonis UPS driver could communicate with a NUT server). I have a second more fancy and expensive UPS that does allow monitoring, but it is running my main computer system, where it does the most good. So an Allonis Poweroff command is sent to Allonis when the main system detects a power failure. 

The "Shutdown" Allonis command just shuts down the Allonis server. The "Poweroff" Allonis command is supposed to shut down the Allonis server, and then power off the Rasberry PI. Poweroff does the first, but only partially does the second. The processor is no longer running. But the internal LED lights are still lit, and pressing the on/off button has no effect. I had to power cycle the Rasberry in order to get it to turn back on.

So the question again is there a method (hidden or otherwise) to get that Rasperry PI to completely shut down?

The driver uses NUT...so maybe that's how you should implement...read the doc...spells it all out.

Sorry Dave, but there is a difference between a NUT server and a NUT client (I did not know either until I did my research). As there is no monitoring capability from the UPS connecting to the Allonis Rasberry PI, running a NUT server on it is useless.

But that still does not answer my question as to how to fully power off the Allonis Rasberry PI. Is this just a restriction that Rasberry PIs have, or is my unit defective somehow? Or is there a secret incantation I am missing?

BTW this thread was accidently put in an incorrect thread group. Perhaps it could be moved to a more relevant group? Thank you.