If the NFS Version 4 client does not recognize a user or group name from the server, the client is unable to map the string to its unique ID, an integer value. Under such circumstances, the client maps the inbound user or group string to the nobody user. This mapping to nobody creates varied problems for different applications.
Because of these ownership issues you may see filesystem has permission of nobody:nobody on the NFS client.
To avoid this situation you can mount filesystem with NFS version 3 as shown below.
On the NFS client, mount a file system using the NFS v3
# mount -F nfs -o vers=3 host:/export/XXX /YYY e.g. # mount -F nfs -o vers=3 hostA:/home/cv/share_fs /tmp/test
If this works fine than make the entry permanent by modifying the /etc/default/nfs file and uncomment the variable NFS_CLIENT_VERSMAX and put entry 3
vi /etc/default/nfs NFS_CLIENT_VERSMAX=3
If you are still getting permissions as nobody:nobody then you have to share the filesystem on NFS server as anon.
share -o anon=0 /home/cv/share_fs
Now try re-mount on NFS Client
mount -F nfs -o vers=3 hostA:/home/cv/share_fs /tmp/test