On the server
Install the Debian packages (on Debian the nfs-kernel-server package contains exportfs)
apt-get install nfs-kernel-server nfs-common nfs-utils
Set up the /etc/exports file (allow 192.168.0.123, read-write, no subtree check)
/media/bigdrive 192.168.0.123(rw,no_subtree_check)
Restart the NFS daemon after editing the exports file
exportfs -ra
On the client
mount 192.168.0.100:/media/bigdrive /media/nfs_bigdrive