### How to disable NFS4 support on a Linux NFS server? ###


NFS is a quite cool protocol - it allows to mount shared disks over the network. The NFS protocol comes in a few versions: NFSv1, v2, v3, v4. There is big difference between v3 and v4, and making both interoperable can quickly become a giant mess. That's why I prefer to stick to only NFSv3, because all my systems are compatible with it (and not necessarily aware of NFSv4). To avoid any troubles, it can be a good idea to explicitely disable NFSv4 support on the server, so you can be sure that it will always use NFSv3.

Here is how I disabled NFSv4 support on my Debian 6.0 NFS storage server.

The file /etc/default/nfs-kernetl-server contains instructions for the NFS server. I couldn't find any setting related to limiting versions of the NFS protocol, so I appended the "--no-nfs-version 4" parameter to another option, like that:
RPCNFSDCOUNT='8 --no-nfs-version 4'

RPCNFSDCOUNT is a parameter that tells how many instances of the NFS server can be used. It's a parameter that is feeded to the NFS server through the command line at launch time, therefore appending anything to it allows to provide "customized" parameters (like the "--no-nfs-version" one, that forbids of using a specific version - in my case the version 4 - of the NFS protocol).