cgroupv1 has been deprecated (will be maintained until May 2029)

[AkihiroSuda]

Moby maintainers agreed to officially deprecate cgroup v1, but maintain it until May 2029 at least:

• Officially deprecate cgroup v1, but maintain it until May 2029 at least moby/moby#51111

So we have to keep maintaining it at least until May 2029.

The latest release in May 2029 does not necessarily need to support cgroup v1, but there should be at least one maintained branch with the support for cgroup v1.

Discussion in other projects

• pid1: stop refusing to boot with cgroup v1 systemd/systemd#34999
  • The support for cgroup v1 was disabled by default in systemd v256 (Jun 2024), and removed in systemd v258 (Sep 2025)
• Remove cgroup v1 support kubernetes/enhancements#5573
  • [KEP-5573]: Remove cgroup v1 support kubernetes/enhancements#5574
• Proposal: synchronize cgroupv1 deprecation announcements runtime-spec#1251
• Officially deprecate cgroup v1, but maintain it until May 2029 at least containerd/containerd#12443