This post is not about doing a PXE-based network installation of Ubuntu. There are already many posts describing how to do this. This post is about setting up an Ubuntu workstation in diskless mode, such as the workstation boots via PXE and the root filesystem is mounted over NFS.
The process consists on the following main [...]

The AutoFS service in Leopard, also known as automount, is configured by means of text files stored in /etc and the automount command-line utility. The standard automount configuration also allows for local directory service lookups and thus can also be configured by using Directory Utility.
The configuration of the automounter starts with the master configuration file, [...]