Prevent Ubuntu asking for the CD to install packages

Recent releases of Ubuntu have a feature where the installation CD can be used as a repository for installing software, just like any repository on the web. The advantage of this, obviously, is it means that you can save bandwidth for some packages that haven’t been updated since the release, or even sometimes be able to install new packages without an internet connection at all. The main disadvantage - the CD has to be in the drive.

And when you get asked for that CD when installing something, and you really don’t feel like finding it on your messy desk, or wherever it’s hiding, it can be frustrating.