doc: clarify Cirrus self-hosted workers setup

[Sjors]

Taken from #29274 (except for two paragraphs that require the other commits in that PR).

[DrahtBot]

The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.

Code Coverage

For detailed information about the code coverage, see the test coverage report.

Reviews

See the guideline for information on the review process.

Type	Reviewers
ACK	maflcko, tdb3

If your review is incorrectly listed, please react with 👎 to this comment and the bot will ignore it on the next update.

Conflicts

Reviewers, this pull request conflicts with the following ones:

• #29432 (Stratum v2 Template Provider (take 3) by Sjors)
• #29274 (Support self-hosted Cirrus workers on forks by Sjors)

If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

[maflcko]

ACK 9f4255a 🌂

Show signature

Signature:

untrusted comment: signature from minisign secret key on empty file; verify via: minisign -Vm "${path_to_any_empty_file}" -P RWTRmVTMeKV5noAMqVlsMugDDCyyTSbA3Re5AkUrhvLVln0tSaFWglOw -x "${path_to_this_whole_four_line_signature_blob}"
RUTRmVTMeKV5npGrKx1nqXCw5zeVHdtdYURB/KlyA/LMFgpNCs+SkW9a8N95d+U4AP1RJMi+krxU1A3Yux4bpwZNLvVBKy0wLgM=
trusted comment: ACK 9f4255ac57929de985425f26ad904a12176a0e85 🌂
UUSQcgPjO07LFUTZUP8JVqqHdsEpkqLnB5MQjPPzt6EDDztzLcIRrJIR/pQPe6hCTTzAK6Yz/mVfi1zCB2FsAA==

[fanquake]

which may work out of the box with podman or docker.

Please don't add vaugeries like this to docs. If you have a specific issue that you're running into, please open an issue, otherwise things should be assumed to be working (otherwise they should be fixed, rather than adding docs claiming they might not work).

[Sjors]

I don't know if it works out of the box for every distro out there. It does for Ubuntu 24.04 when used with podman, at least after a reboot. I haven't tested with docker nor on any other distro. The documentation for https://github.com/multiarch/qemu-user-static says you need to run sudo podman run --rm --privileged multiarch/qemu-user-static --reset -p yes first, but this is not (no longer?) true.

What I'm trying to convey with "may work" is: it might work with just sudo apt install qemu-user-static, even though the projects own README says it doesn't. I can change it to "works", but that might be wrong - hard to know without trying every permutation out there.

[Sjors]

This uncertainty is also part of the reason #29274 adds NO_ARM as an option.

[fanquake]

I don't know if it works out of the box for every distro out there

That's fine. Just assume it does until we know otherwise.

[Sjors]

Ok, changed to "works" and added a link that explains what this does.

[Sjors]

Fixed @maflcko's nits.

[tdb3]

Approach ACK.
This adds more clarity to CI config, much appreciated.
Left a comment and thought.

[tdb3]

These specs will become outdated over time (e.g. Ubuntu 23.04 which is already obsolete). Maybe instead it would be better to point the reader to doc/dependencies.md (or doc/build-unix.md, etc.)? dependencies.md doesn't currently specify distro versions, but would it be the case that dependency versions are really what matters, and distro version is a downstream consequence of that?

Perhaps this is a little less easy for the reader but helps prevent this file from becoming stale. Something like:

- # Generally, a persistent worker must run Ubuntu 23.04+ or Debian 12+.
+ # Generally, a persistent worker must run a distribution that supports the minimum dependencies in `doc/dependencies.md`

[maflcko]

This is just a moved sentence and still correct. 23.04+ is required, and should work, if someone manages to install it.

[maflcko]

Also, your suggestion is incorrect. doc/dependencies.md has nothing to do with a CI system runner. In fact, you can probably use any distro, as long as you can install podman4.1+ or docker on it.

[tdb3]

Good point about the +. The thought was "Is there a way to describe what the needs are while minimizing the future changes needed to this file?" If we think pointing elsewhere (e.g. to a place that describes the needs, but is being updated for additional reasons beyond this file) is overkill, then we don't need to change this line.

[maflcko]

If we think pointing elsewhere (e.g. to a place that describes the needs, but is being updated for additional reasons beyond this file) is overkill, then we don't need to change this line.

The file is self-contained regarding this line and there is no need to point elsewhere. "podman4.1+" is equivalent to "vanilla Ubuntu 23.04+" (forever), so there is no need to update it in the future.

[tdb3]

This one I'm a little torn about. Ideally, these machine specs would change less frequently than Linux distro versions (a side effect of keeping node requirements modest/reasonable), so maybe it makes sense to leave these specifics in this file.

[maflcko]

Not sure what you mean. This is just a moved section to explain the three possible and required labels.

[tdb3]

Initially, the thought was similar to above, if specs change, do we want to come back to this file and adjust them here, or would it be better to have a place that we can point to for minimum/recommended specs more generally or globally (since building and running tests happen for development in general rather than solely in CI)?
If these specs won't change very frequently, then it's not a big risk to keep them here and update this file over time.

[maflcko]

This file .cirrus.yml is self-contained and only concerns Cirrus CI. It has no meaning for the outside CI system. The labels are used in this config file only, they are only required here, and they are explained here.

[maflcko]

ACK 66b9740

[maflcko]

ACK c67f215

[tdb3]

ACK c67f215