Compressing packages with bzip2 instead gzip?

Aigars Mahinovs aigarius at
Wed Jan 18 20:00:35 GMT 2006

On 1/18/06, Phillip Susi <psusi at> wrote:
> The required change is rather straightforward; you just extract and
> decompress the members of the .deb, zsync, then recompress and rebuild
> the deb.  What's so hard about that?

Only advantage of zsync over rsync is that there is no software
running on the server side at download time. It is only nessesary to
generate a .zsync file for every file to be downloaded by zsync. So
server can not decompress the .deb.

The idea of zsync is that the client downloads (via HTTP) the .zsync
file, uses rolling MD4 and MD5 checks to determine which parts of the
local file are different from the file on server, and then uses a HTTP
request for a part of file (from byte x untill byte y) to get the
different chunks.

The problem is in the metainformation that has to be generated on the
server side. The .zsync files contain would need to contain filenames
of all files in the .deb, MD5 sums of every file and a rolling MD4 sum
of every file (to detect parts of file that have changed) and (the
hard part) they would also need to include some kind of information
that the client could use to determine where this file will be located
in the compressed .deb (address, in bytes).

Best regards,
    Aigars Mahinovs        mailto:aigarius at
 |     .''`.         Debian GNU/Linux              LAKA         |
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 |    `. `'                                                     |
 |      `-                                                       |

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