As we may know already that, tape device are in “/dev/rmt” directory. Actually tapes creates symbolic links in the “/dev/rmt” directory to the actual tape device special files under the “/devices” directory tree. tapes searches the kernel device tree to see what tape devices are attached to the system.
Each tape LUN seen by the system is represented by 24 minor nodes in the form of /dev/rmt/N, /dev/rmt/Nb, and /dev/rmt/Nbn, where N is an integer counter starting from 0. This number is picked by devfsadm during enumeration of new devices. Every new tape logical unit number (LUN) found by devfsadm gets the next available number in /dev/rmt.