Comment 7 for bug 191378

I don't think acng is config-file compatible with apt-cacher. acng has several interesting features (like backend redundancy) that apt-cacher doesn't. Since I first posted on this bug, there have been at least one upstream release of each.

I've been using squid and apt-cacher and I have to say they both fit the bill. For vm building, an apt-cacher or acng solution would be preferable, since in squid you generally want files to drop out of cache when not used, and files in main will drop relatively quickly if not refreshed. On the other hand, squid works really well for keeping systems up to date once you've built them, and a lot of things that make life easier running systems (like seeing changelogs in update manager). Squid tends to handle things like do-release-upgrade better, though apt-cacher now has support for that.

There's the possibility of a hybrid solution as well, using jesred (a redirector for squid) that redirects ubuntu archive requests to apt-cacher or one of its siblings:

http://www.porcheron.info/bandwith-optimization-squid-apt-cacher-and-jesred/

This could be adapted to acng trivially.