There is currently no way in the RESTAPI to check if a virtual machine is in "run once" mode.
Verify with orirt 3.6: oVirt Engine Version: 3.6.0-0.0.master.20150412172306.git55ba764.el6 Steps to check: 1. Create new VM and run it with "RunOnce" 2. Connect to REST API and check for the VM the status of "run_once" Result: <run_once>true</run_once> 3. Check for VMs that are not "run_once" the status: Result: <run_once>false</run_once>