Comment 17 for bug 671027

For d-i, a special type of stripped down .debs is used (udebs) and these are installed in special packages indices in the archive; these are not supposed to be installed on an end-user system, only when creating d-i images. However images using ubiquity are essentially like a installed system, so ubiquity has a script to pull a copy of all the latest udeb into its package, and embeds all udebs it calls. It's a copy, but in a way this avoids code duplication between d-i and ubiquity images.