While building my own nas system (basically, I originally tried using Open-e NAS, but was frustrated because they wanted to charge me €400 to upgrade to a version that includes rsync capabilities), I needed to install a nfs server.
To make sure certain directories are available through nfs, you have to edit the /etc/exports file, adding lines like
/home 192.168.0.0/24(rw)
No idea why you would need a nfs-server to build your own nas-system : would you care to explain ?
Because, when connecting from a different linux machine, it is much more practical to use nfs than smb (samba).