The next step after the %Debian 11 bullseye upgrade is, of course, the Debian 12 "bookworm" upgrade.

Debian bookworm was planned to be released some time in 2023 and was released on June 10th 2023. Debian bullseye will be supported until June 2024, so that's our deadline.

We typically start upgrading our boxes when testing enter freeze, so we might even want to start working on this in early 2023, setting the start date accordingly. Unfortunately, we haven't been able to complete the bullseye upgrade in time for the freeze, as complex systems required more attention. See the post-mortem for a review of that approach.

The schedule for this project was adopted in TPA-RFC-57, here's an excerpt:

The upgrade is split in multiple batches:

• low complexity (mostly TPA services): 34 machines, September 2023 (issue 41251)
• moderate complexity (service admins): 31 machines, October 2023 (issue 41252)
• high complexity (hard stuff): 15 machines, to be announced separately, before June 2024 (issue 41321, issue 41254 for gnt-fsn and issue 41253 for gnt-dal)
• to be retired or rebuilt servers: upgraded like any others
• already completed upgrades: 4 machines
• buster machines: high complexity or retirement for cupani (tpo/tpa/team#41217) and vineale (tpo/tpa/team#41218), 6 machines

The free time between the first two batches will also allow us to cover for unplanned contingencies: upgrades that could drag on and other work that will inevitably need to be performed.

The objective is to do the batches in collective "upgrade parties" that should be "fun" for the team. This policy has proven to be effective in the bullseye upgrade and we are eager to repeat it again.

As of 2023-09-26, we're slightly late in our July 2024 objective, as the predicted upgrade date is 2023-09-26 according to https://gitlab.torproject.org/tpo/tpa/team/-/wikis/howto/upgrades/bookworm#per-host-progress

Update: the bullseye upgrade ran really late and is not threatened to be incomplete before LTS drops support, so that will be prioritized over the bookworm upgrade, which is done for the most part. So the due date has been pushed back explicitly. Actual progress has improved significantly since that last update above, with an estimated date of 2024-07-06, but that will likely be missed.