Specifies the port number used for RPC listener sockets.
If this option is not specified,
.B rpc.mountd
-chooses a random ephemeral port for each listener socket.
+will try to consult
+.IR /etc/services ,
+if gets port succeed, set the same port for all listener socket,
+otherwise chooses a random ephemeral port for each listener socket.
.IP
This option can be used to fix the port value of
.BR rpc.mountd 's