Packages file contains extra unnecessary hashes

[Robie Basak]

Packages files (eg. http://archive.ubuntu.com/ubuntu/dists/jammy/main/binary-amd64/Packages.xz) contain hashes using MD5sum, SHA1, SHA256 and SHA512, but if we deprecate the older ones and leave only SHA512 (for example), then we get a 30% or so size saving, reducing the "apt-get update" download size of a typical system by 5-10 MB when there is no cache (eg. on every cloud instance boot). This seems worth adding to a backlog.

I think we need to track:

Launchpad support for per-series compatibility level, so that we can reduce the set of published hashes in newer releases without affecting old ones.

Actually making the change in Ubuntu.

Possible changes in affected tooling as these are discovered.

ML thread here: https://lists.ubuntu.com/archives/ubuntu-devel/2024-May/042978.html

[Robie Basak (racb)]

Size-based benefit analysis here: https://lists.ubuntu.com/archives/ubuntu-devel/2024-May/043006.html

[Jürgen Gmach (jugmac00)]

Hi Robie, thanks for raising this. It might be a good idea to discuss this with Clinton to raise awareness and to make a case for this to be included in our next roadmap.

[Julian Andres Klode (juliank)]

This is a duplicate of bug 1883271 and a merge proposal to fix it is in https://code.launchpad.net/~xnox/launchpad/+git/launchpad/+merge/452749