Re: .deb format: let's use 0.939, zstd, drop bzip2

[Thomas Goirand <zigo@debian.org>]

On 5/9/19 6:25 PM, Andrej Shadura wrote:
> Hi,
> 
> 
> On Thu, 9 May 2019, 15:57 Ian Jackson, <ijackson@chiark.greenend.org.uk
> <mailto:ijackson@chiark.greenend.org.uk>> wrote:
> 
>     Ansgar writes ("Re: .deb format: let's use 0.939, zstd, drop bzip2"):
>     > `ar` needs to be replaced for the file size limitation mentioned
>     in the
>     > initial mail: ar represents file size as a 10 digit decimal number[1]
>     > which limits the members (control.tar.*, data.tar.*) to ~10G.
>     ...
>     > Replacing `ar` is an incompatible format change.  So if we already do
>     > an incompatible change, it is an appropriate time to bundle any other
>     > incompatible changes (if there are any).  That is why I suggested that
>     > it might be useful to also replace the `tar` archives with another
>     > format.
> 
>     As has been pointed out, we have done many incompatible format
>     changes.  Every new compression algorithm is one.  It isn't really a
>     big problem, when managed properly.
> 
>     So I strongly disagree.  The archive size limit is getting more and
>     more annoying.  We should not let fixing that be entangled with some
>     random other nice-to-haves.
> 
>     Personally I still like my multi-ar-member proposal here
>       https://lists.debian.org/debian-dpkg/2016/05/msg00027.html
>     Guillem didn't seem entirely unreceptive but nothing came of it.
> 
> 
> 
> How about the format opkg used for some time, which is a .deb file but
> with tar as the outer container format instead of ar?

This is a very bad idea. When installing a large amount of packages, apt
needs to uncompress all control.tar.gz files so it can get the config
and templates of debconf. With tar, meaning without an index, one may
need to uncompress the whole of the .deb file in order to extract just a
tiny portion of it. This could potentially be super long (think: a
dist-upgrade with so many packages...).

Cheers,

Thomas Goirand (zigo)