Manually installing the package keyutils got nfsidmap(5) working for me.
See the Linux kernel documentation [1].[1] /usr/share/doc/linux-doc-4.6/Documentation/filesystem/nfs/idmapper.txt.gz
-- Stig Inge Lea Bjørnsen stigi...@pvv.org
I had the same issue on Debian Sid without nfs-kernel-server installed,
rpc.idmapd is no longer running.
- Bug#830777: nfs-common: rpc.idmapd does not start ... Stig Inge Lea Bjørnsen
- Bug#830777: nfs-common: rpc.idmapd does not s... Andreas Henriksson
