libvirt-pre-reboot.py

#!/usr/bin/env python
"""
One of my machines runs multiple KVM vm's.

When the host needs to reboot i suspend the vm's first using this quick and dirty script.
After the reboot there is some time skew in the vm's (they continue at the time of the 
suspend). You either need to use one of these solutions;
  * reboot the vm's. They will pickup the correct time...
  * manually stop ntp (service stop ntp) and let ntpd fix the time with a large step (ntpd -gq)
  * setup ntp to skew the clock faster
  * setup KVM to provide a different clocksource <https://access.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Virtualization_Administration_Guide/sect-Virtualization-Tips_and_tricks-Libvirt_Managed_Timers.html>
  
Since I don't reboot often I have not setup the clocksource yet...
"""
import libvirt

conn = libvirt.open(None)

for id in conn.listDomainsID():
   domain = conn.lookupByID(id)
   #domain.shutdown()
   domain.managedSave(0)