When aptitude is run in interactive mode, it shows a list of Virtual Packages > virtual, which is 8267 lines long on my jessie laptop. Where does aptitude get this list from? Does it laboriously construct it from Provides:, Replaces:, and Conflicts: lines in the Packages files and then cache it to speed things up? If not, where is there a list of such packages that dates from post-2012? Cheers, David.