FWIW, this still happens when both client & server are running Linux 3.11.0-rc5 (vanilla). $ dpkg -l | grep nfs | cut -c-70 ii libnfsidmap2:amd64 0.25-4 amd64 ii nfs-common 1:1.2.6-4 amd64 ii nfs-kernel-server 1:1.2.6-4 amd64