I've looked at some ways to accelerate the build script to make building Whonix less painful. This is a very long-term item because breaking the script is serious problem and because other priorities but its definitely something worth doing at some point.
Low hanging fruit:
- Download one set of all packages and make a copy for the other image if gnw is selected to avoid downloading the same things twice. This alone would halve the time.
- Parallelizing apt downloads using xarg - the older method before GNU Parallel's conception. Code licensed under Attribution-NonCommercial-ShareAlike 2.5 Generic
http://tinylittlelife.org/?p=283 (inspired by the post beneath it)
- Taking this further the image generation step can be done in parallel too though time savings will be less compared to download time reduction.
Disqualified but worth noting:
I found the tool "apt-fast" which downloads one or two files quickly, by downloading with multiple streams per file. This is somewhat sketchy, as it requires installation of additional software, assumes the file gets spliced together correctly, and doesn't gracefully handle network problems.
- apt-fast - an apt wrapper that downloads package chunks from multiple mirrors in a "bittorrent-esque" way. If you are interested in it I could request the author gives it a license.