I’m currently using the RPi2 as a NAS, sharing a 5TB USB HDD via SMB (NTFS). Are there instructions somewhere that outlines step-by-step how to set up an NFS server? I’d like to maximize performance as much as possible. (I’ll be converting to ext4 eventually as well).
sudo apt-get install nfs-kernel-server
Well @sam_nazarko gave you the info how to install it. If you need help how to configure. OSMC is Debian based, so googleling “how to NFS server Debian” should give you some ideas
Is there any way to set up NFS shares from within the GUI?
I assume you mean shares for the NFS server you installed on OSMC? If that is the case the answer is no. Via the GUI you only can add shares as sources.
But to configure the NFS shares for the server is a onetime step so just connect via SSH and edit the file.