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Re: Jigdo and BitTorrent (was Secondary CD/DVD Image Downloading)

On Sun, Aug 31, 2008 at 09:47:39PM -0400, Daniel Dickinson wrote:
> I'm interested.  I know nothing of jigdo, but this would allow me to
> make torrent images available more quickly.  Also, can you do this with
> any pool (such as one from apt-cacher-ng)?

As long as its creates a cache directory (or directory tree) with
.deb files in, Jigdo can use it.  It will also use .debs from
old CDs/DVDs, even if they weren't downloaded with Jigdo.


The fact that you can use the apt cache is currently buried in the
HOWTO's errata section.

Quick overview of the bittorrent trick:
This isn't my idea, but I can't find where I learned this from to
acknowledge the inventor.

Once Jigdo has finished finding .debs on your PC, it would
normally complete the ISO by downloading the missing files from a
mirror.  At this point press ctrl-C, and it will leave an .iso.tmp
file which is the DVD (and a valid filesystem), except that the
missing .debs appear as files of the right size with their content
filled replaced by zeros.

Move the .iso.tmp to the location that BitTorrent / BitTornado
would download it to (with default BT settings, just rename it to
.iso).  BT will check the existing data for corruption, using the
checksums in the .torrent file.  Any block that was completely
filled in by Jigdo will check correctly; the rest will be marked
as corrupt and downloaded again via bittorrent.

(TODO: check the behaviour of other bittorrent implementations,
and write this in a more accessible way.)


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