Diff-debs: what options are used for gzip compression in .deb files?

John C. McCabe-Dansted gmatht at gmail.com
Sat Jan 14 08:06:23 GMT 2006

On Friday 13 January 2006 22:00, Michael Vogt wrote:
> I personally like the zsync based approach most, because it makes the
> handling of diffs uniform, we can zsync Packages.gz, Sources.gz,
> Content.gz, *.deb, *.tar.gz with it.

Apparently zsync has the problem that it doesn't preserve the gz compression 
in the debian data.tar.gz files, so you have to do
  gunzip | gzip
to get a data.tar.gz  for which the md5sum matches.

However, I cannot figure out which gzip&options ubuntu uses to create 
data.tar.gz (in this case from kamera_4%3a3.5.0-0ubuntu0breezy1.2_i386.deb, 
extracted using ark).

wc -c data.tar.gz 
    && gunzip < data.tar.gz | gzip | wc -c 
    && gunzip < data.tar.gz | gzip -9  | wc -c

gives me:

85795 data.1.2.tar.gz

So it seems ubuntu doesn't use /usr/bin/gzip to generate data.tar.gz, with 
either default compression or --best compression.  Why not? It seems like 
--best would save space (1k in this case) if nothing else.

John C. McCabe-Dansted
Masters Student

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