Debian stretch allow only nfs version 4.1 or higher

Question

I am running Debian 9.0 (Stretch) with nfs-kerner-server from the repositories.

How can I restrict connections with protocol version lower then 4.1?

Answer 1

There is is configuration file /etc/nfs.conf where you can specify which nfs versions nfsd server must offer:

[nfsd]
vers2=n
vers3=n
vers4=n
vers4.0=n
vers4.1=y
vers4.2=y