Proxmox: NFS access denied

on CT / LXC NFS client side:
mount.nfs: access denied by server while mounting...

The problem was on proxmox side. Proxmox have apparmor and that thing is blocking everything.

To stop apparmor and make him not work, do this steps

# /etc/init.d/apparmor stop
# /etc/init.d/apparmor teardown
# update-rc.d apparmor disable

REF: https://askubuntu.com/questions/897411/nfs-access-denied-by-server-while-mounting-client-side-is-a-lxc-proxmox