$ sudo vi /etc/fstab
192.168.30.26:/root/backup /usr/backup nfs rw,noauto,user 0 0
In the above, "user" allows a non-root user to mount, and "noauto" means no automatic mount on boot.
If you want to enable export non-permanently (which is not persistent across reboots):
$ sudo exportfs 192.168.30.26:/export -o rw,async,no_root_squash,no_subtree_check
If you want to enable export permanently (which is persistent across reboots):
$ sudo vi /etc/exports
$ sudo exportfs -a
Now you can log in as "user" on the NFS client host, and do NFS mount as follows.
$ mount /usr/backup