I recently learned about unionfs and aufs and would like to put it to some real use. The scenario I have in mind is the following. Boot a machine with ubuntu on it which will serve as our base. Make sure the root partition for the base is ro. Overlay an empty rw partition over the root partition using unionfs or aufs magic. Go to town on the system and maybe break some things. Now instead of wiping and re-installing everything from scratch I can just wipe the rw partition and reboot the system to restore it to a working state.
So I want to know what I need to learn to accomplish the above task. Googling for aufs/unionfs has already brought up things like initramfs and I would like to know what other keywords I should look up if I want to do this right.