From Birnam Designs Wiki

From the host machine, make sure nfs software is installed. In Ubuntu:

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

Then edit the /etc/exports file:

/home/user/folder 192.168.1.1/24(rw,no_root_squash,async)

And make the share effective with:

sudo exportfs -a

This will share /home/user/folder with everybody in 192.168.1.*

On the guest computer, if you want the mount to happen at startup, create the mount folder (e.g. /mnt/folder) and edit /etc/fstab

192.168.1.2:/home/user/folder /mnt/folder nfs defaults 0 0