Ubuntu 12.04 NFS v4 mount error incorrect mount option was specified

Question

I am trying to mount a nfs folder over network from NFS Server to NFS Client.

My NFS Server configuration looks like this

/mount     192.168.145.128/255.255.255.0(rw,sync,no_subtree_check) 127.0.0.1/255.255.255.0(rw,sync,no_subtree_check)

I have installed all required packages ( nfs-kernel-server nfs-common) on my server.

I have also restarted the server using the option:

service nfs-kernel-server restart

At client end, I check the folder list that I can mount using

showmount -e 192.168.145.131
Export list for 192.168.145.131:
/mount 127.0.0.1/255.255.255.0,192.168.145.128/255.255.255.0

But when I try mounting the host folder, I get the following error:

mount -t nfs -v 192.168.145.131:/mount mount/
mount.nfs: timeout set for Fri Apr 18 17:34:44 2014
mount.nfs: trying text-based options 'vers=4,addr=192.168.145.131,clientaddr=192.168.145.128'
mount.nfs: mount(2): Invalid argument
mount.nfs: an incorrect mount option was specified

This is my dmesg output:

dmesg | tail
[24930.733208] NFS: bad mount option value specified: vers=4

Solution

I was getting the incorrect mount option error after I upgraded to Ubuntu 14.04. What worked for me was to specify the nfsvers option:

mount -t nfs -o nfsvers=3 machine:/ /mountdir