Objective

Move the CI and Atlas CI workflows from ubuntu-22.04 to ubuntu-26.04 when a released MongoDB server accepts the kernel version strings that Ubuntu reports.

Why the runners are pinned to ubuntu-22.04

MongoDB 8.0 exits at startup when uname reports a kernel between 6.19 and 7.0.13 (startup_check_rseq, SERVER-121912). The ubuntu-24.04 runner reports 7.0.0-1017-azure and the ubuntu-26.04 runner reports 7.0.0-1019-azure. Ubuntu keeps the release string at X.Y.0, so the 7.0.14 exemption added in 8.0.30 never matches. mongo:8.0 still resolves to 8.0.34, so the container only starts on ubuntu-22.04 (kernel 6.8).

The analysis of the original failure and the resource list are in the comments below.

Blocked by

SERVER-136848, fixed by SERVER-131779: the server reads /proc/version_signature on Ubuntu instead of relying on uname -r. The backports target 8.0.35 and 8.3.14. The v9.0 backport is released, and the mongodb/mongodb-atlas-local image already embeds 9.0.4.

Work to do when unblocked

• Set runs-on to ubuntu-26.04 in .github/workflows/build-ci.yml and .github/workflows/build-ci-atlas.yml, and update their comments.
• Set the crypt_shared target to ubuntu2404 in the crypt_shared_version.php call and in the cache key. It is the newest target published in the MongoDB download manifest, there is no ubuntu2604 target.
• Remove the kernel paragraph from AGENTS.md.
• Check that mongo:8.0 resolves to 8.0.35 or later, because the matrix pins that tag.
• Check that the CI and Atlas CI runs are green on ubuntu-26.04.

Deadline

The ubuntu-22.04 runner image is deprecated since 2026-09-17 and unsupported after 2027-04-17.