docs: def _delete_vdev_info(self, vdev):
          """handle udev rules file."""
          vdev = vdev.lower()
          rules_file_name = '/etc/udev/rules.d/51-qeth-0.0.%s.rules' % vdev
          cmd = 'rm -f %s\n' % rules_file_name
  
          address = '0.0.%s' % str(vdev).zfill(4)
          udev_file_name = '/etc/udev/rules.d/70-persistent-net.rules'
          cmd += "sed -i '/%s/d' %s\n" % (address, udev_file_name)
          cmd += "sed -i '/%s/d' %s\n" % (address,
                                          '/boot/zipl/active_devices.txt')
          return cmd