Automatically saves the state of all running KVM guests when the system is shut down put into /etc/init.d and reference from /etc/rc0.d and name it with a prefix which makes it execute before any of the other scripts (for instance K01)

save-vms.sh

#! /bin/sh

suspend_vms () {
  for output in $(virsh list --state-running --uuid)
  do
    exec virsh managedsave $output --bypass-cache
  done  
}

case "$1" in
  start)
    # No-op
    ;;
  restart|reload|force-reload)
    echo "Error: argument '$1' not supported" >&2
    exit 3
    ;;
  stop)
    suspend_vms
    ;;
  *)
    echo "Usage: $0 start|stop" >&2
    exit 3
    ;;
esac

: