Changing update method after install w/o GUI

[jennyw]

During the install of Ubuntu Server, we get asked: "How do you want to manage upgrades on this system?". I've always chosen "No automatic updates". But if I wanted to change this after the install, what's the way to do that? I've seen info on how to do it with the GUI, but this is a server -- which for us means text-only.

Thanks!