this is a very quick walk through on setting up ubuntu (tested with Ubuntu 6.06.1 LTS \n \l as a straight forward nfs share on sparc platform (even though its identical on x86).

this entry assumes you want to share with everyone on your network.

update your apt-get first
sudo apt-get update

install nfs-common, nfs-kernel-server and portmap
sudo apt-get install nfs-common nfs-kernel-server portmap

sudo vi /etc/exports and add this:
/path/to/share *(rw)
**remember to change /path/to/share with your share

sudo vi /etc/hosts.allow and add this:
ALL: ALL

make sure that portmap is running
sudo /etc/init.d/portmap start

restart nfs-common and nfs-kernel-server
sudo /etc/init.d/nfs-common restart
sudo /etc/init.d/nfs-kernel-server restart[

now mount your share from a remote computer
sudo mount server:/path/to/share /mountpoint