nfsv4 domains

Hi,

Testing the impact of enabling NFSv4 (via our OneFS Simulator) and not having consistent results from centos/RHEL.

Ubuntu seems to be fine. NFSv3 is fine, and forcing mounts to user vers=3 workaround works, however we can't seem to understand the NFSv4 implementation.

centos/RHLE return

mount.nfs: Operation not permitted 

This occurs even adding the clients as root clients to the NFS export. 

I dont fully understand what the NFSv4 domain really is, do we need to setup identical accounts on the client and a local account on the powerscale cluster so they match? or can we somehow use AD (which is what we use for windows shares) for authentication?