RHEL - NFS4: Mounted/Exported as rw, user write permission denied

Solution 1:

I have the exact same issue and found out what the problem is: the problem is that nfsv4 uses idmapd and idmapd does mapping between userid => names but not the other way around. In other words, it can't work. It is just fancy and confusing to see the correct permissions user and group, however when you use the filesystem it will still use the old way of mapping through uid. So the uid on the server side should be the same as on the client side for that user. Otherwhise creating files, ... will fail with permission denied. Unless the uid match of course.

reference: http://thread.gmane.org/gmane.linux.nfsv4/7103/focus=7105