def unmount_volume_groups(self):
        """Unmounts all volume groups and related loopback devices as identified by :func:`find_volume_groups`"""

        for vgname, pvname in self.find_volume_groups():
            _util.check_output_(['lvchange', '-a', 'n', vgname])
            _util.check_output_(['losetup', '-d', pvname])