Device is not known to local system.  On the device field, press PF3.

    Meaning:  You entered a device name of a device that is not connected
              to your system.

    Action:   Select a device that is connected to your system.  Press
              PF3 to display a box of known disk devices.  Use the arrow
              keys to scroll through the selection options, and press
              Return to select a device.  Selecting a device from this
              box places the selection in the name field.

              If you do not want to select a disk device press PF3 again
              (or Ctrl/Z) to cancel the box.