Practice 

The given example displays the list of clients on that file system are mounted

# showmount

hostname on radiant1:/home/Krishen

Here radiant1 is the client on that /home/Krishen file system is mounted.

Options

-a or -all

Lists the client hostname and mounted directory both in host:dir format.

-d or -directories

Lists only the directories mounted through a few clients.

-e or -exports

The file /var/lib/nfs/rmtab holds a record of all clients which mount remote file systems from the current machine. Every time a remote mount is completed, an entry is made in the rmtab file of the machine serving in which file system. umount removes the entry of a remotely mounted file system. umount -a broadcasts to all servers which they should remove all entries from rmtab. It holds a table of filesystems which are remotely mounted through NFS clients. This file is maintained through mountd the mount daemon. A data in this file should be obtained only from mountd the mount daemon the file holds a line of information for every remotely mounted filesystem.

Let consider the following example

# vi      /var/lib/nis/rmtab

radiant1           /home/Krishen

radiant2           /home/rams

In the given file /home/Krishen is being accessed through radiant1,/home/rams is being accessed through radiant2.