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




(adding debian-dpkg)

Adam Borowski writes (".deb format: let's use 0.939, zstd, drop bzip2"):
> First, the 0.939 format, as described in "man deb-old".  While still being
> accepted by dpkg, it had been superseded before even the very first stable
> release.  Why?  It has at least two upsides over 2.0:

What an interesting proposal.  I don't think I agree, but:

> * there's no 10¹⁰ bytes (~9.31GB) limit
>   While no package this big is in the archive _yet_ (max being 1⎖652⎖244⎖360
>   bytes), both storage sizes and software bloat grow pretty fast, thus we'll
>   break this barrier in a few years.  And there's a world outside the
>   official archive -- I bet someone already has been burned by this limit.

This is a problem.

> * it's faster by a small but non-negligible factor.  A task "unpack all
>   packages in default XFCE GUI install" gets done by stock dpkg (after
>   repacking everything as gzip) 3% faster.

I'm not sure why it should be faster.

As the person who deprecated deb-old in favour of the current format,
my motives were:
 - the old format was a real pain to unpack without a custom utility
    (this used to be a much more serious problem)
 - the old format was not very extensible.

Debian doesn't really use much of the extensibility.  Some people
invented a .deb signing system which put signatures in there too but I
don't think any such things are deployed.

We use the extensibility for compression format changes, but
compressors all have magic numbers and we could just use those.

It would be much less convenient to change our archive format from tar
to something else, as proposed by Ansgar, without this extensibility.
(I don't necessarily think Ansgar's idea is a good one, but it makes
an example here.)

As for the size limit, this was discussed in May 2016:
  https://lists.debian.org/debian-dpkg/2016/05/msg00027.html

(I can't find a bug about it, though).  I made a proposal.
No decision was made and nothing was done, unfortunately.

Ian.


-- 
Ian Jackson <ijackson@xxxxxxxxxxxxxxxxxxxxxx>   These opinions are my own.

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