Dear John, Bob and Peter, I apologize for the belated replay and thanks a lot for your suggestions.
We believe the problem was not related to ownership and permissions but, instead, related to the xfs file system. In fact, at boot the ROACH2 nfs client uses by default the NFSv2 protocol to mount the remote file system, but this version has some issues in exporting xfs partitions. To fix this problem it is possible to configure the NFSv3 protocol for the booting procedure by editing the /etc/dnsmasq.conf as follow: dhcp-option=net:roach2,17,192.168.40.1: /home/nfs/roach2/current,nolock,nfsvers=3 instead of  dhcp-option=net:roach2,17,192.168.40.1:/home/nfs/roach2/current,nolock Now all the system is working properly. Best, ag.
