Running security updates on debian based systems managed with libvirt and accessible via ssh.

update-virtual-machine

#!/bin/sh

# Running security updates on debian based systems managed with libvirt and
# accessible via ssh.

# Tmux, virsh and ssh are needed for this script.

vms=`virsh list --name`

if [ -z "$TMUX" ]; then
  echo "Create tmux session before installing updates:"
  echo "  tmux new"

  exit 1
else
  echo Update VMs ${vms}.
  echo

  for vm in $vms; do
    tmux new-window -n $vm "ssh $vm '\
      aptitude update && \
      aptitude safe-upgrade && \
      echo && \
      echo Updating done && \
      sleep 60'"
  done

  echo "Check tmux tabs for interaction."
fi

exit 0

If you don't want to bother checking if the upgrades are good (this has become sort of feasible with apt-key), have a look at unattended-upgrades.