Comment 13 for bug 234185

Hans, one problem is that the installer initrd has no idea whether is was booted from a USB drive or not, so the question whether to just scan for USB automatically can not be based on this. On the other hand, I don't see that it can do much harm to scan all USB devices anyway. cdrom-detect already checks for .disk/info. The current situation is not 100% foolproof either, for instance there can be several CD drives each with a different Ubuntu CD and one could be booted while the other is picked for package scan.