Hmm i would recommend just libc6 since nothing in the 'deb' currently calls bzip2... these files are so big you should probably leave that to user to manage.. if that means using zip instead, well thats what i would do... your increasing rate of failure by automating extraction... i'd rather get asked howto then error messages. If you do include extract logic in deb, i would make icon or command for it instead of postinst.... 20 minute installer cylons are not pleasant.