When your Services For Unix (SFU) version 2.0 client tries to mount an NFS share on a Linux server, they receive:

svc: unknown version (3).

Linux currently supports NFS version 2.0, but SFU attemps to connect using NFS version 3.0.

You can disable NFS version 3.0 support in SFU by using Regedt32 to navigate to:

HKEY_LOCAL_MACHINE\Software\Microsoft\Client for NFS\CurrentVersion\Default

On the Edit menu, Add Value name DisableV3 as a REG_DWORD data type. Set the data value to 1.