code: def _build_command(self):
          
  
          command = [self._path]
          if len(self._ethernet_adapters) != 2:
              command.extend(["-e", str(len(self._ethernet_adapters))])
          if len(self._serial_adapters) != 2:
              command.extend(["-s", str(len(self._serial_adapters))])
          if not self.use_default_iou_values:
              command.extend(["-n", str(self._nvram)])
              command.extend(["-m", str(self._ram)])
  
          # do not let IOU create the NVRAM anymore
          #startup_config_file = self.startup_config_file
          # if startup_config_file:
          #    command.extend(["-c", os.path.basename(startup_config_file)])
  
          if self._l1_keepalives:
              yield from self._enable_l1_keepalives(command)
          command.extend([str(self.application_id)])
          return command
docs: Command to start the IOU process.
          (to be passed to subprocess.Popen())
  
          IOU command line:
          Usage: <image> [options] <application id>
          <image>: unix-js-m | unix-is-m | unix-i-m | ...
          <application id>: instance identifier (0 < id <= 1024)
          Options:
          -e <n>        Number of Ethernet interfaces (default 2)
          -s <n>        Number of Serial interfaces (default 2)
          -n <n>        Size of nvram in Kb (default 64KB)
          -b <string>   IOS debug string
          -c <name>     Configuration file name
          -d            Generate debug information
          -t            Netio message trace
          -q            Suppress informational messages
          -h            Display this help
          -C            Turn off use of host clock
          -m <n>        Megabytes of router memory (default 256MB)
          -L            Disable local console, use remote console
          -l            Enable Layer 1 keepalive messages
          -u <n>        UDP port base for distributed networks
          -R            Ignore options from the IOURC file
          -U            Disable unix: file system location
          -W            Disable watchdog timer
          -N            Ignore the NETMAP file