But when the machine aren't real sometime wrong can happened.
Latest server that I had configurated are not real, but run on LXC linux container.
After several google search a lot of test finally I accepted the fact that NFS server on LXC is actually not supported. So, what can I do?
Ok, if NFS server on LXC can't run I always try to run NFS server on real server and configure all the virtual machine as NFS client, so I try to do it.
Again, NFS client on LXC seems do not work. Why? The problem is apparmor on the real machine that block any appempt to mount NFS volumes.
In order to try to minimize the security changes on apparmor I add the following lines in /etc/apparmor.d/lxc/lxc-default
and now all run perfectly.