In natty we got a new tool called “apt-clone”. Its a commandline application that can be used to clone the packages state of a system and restore it on another system. It will save the full state (sources.list, packages/versions installed, auto-installed inforrmation) and optionally using dpkg-repack in order to save not/no-longer downloadable package (like debs that got installed manually via e.g. gdebi or dpkg -i). The file is pretty small because it just stores references to the files in the archive. One nice feature of the restore is that it can be applied to a different root directory (creating a chroot). I use this to reproduce upgrade issues and its really handy for this. Whats missing currently is modified conffiles detection, but there is some work on this in trunk.