KEP-4033: cgroup driver from CRI beta blog

content/en/blog/_posts/2024-08-21-cgroup-driver-from-cri.md

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+---
+layout: blog
+title: "Kubernetes 1.31: Autoconfiguration For Node Cgroup Driver (beta)"
+date: 2024-08-21
+slug: cri-cgroup-driver-lookup-now-beta
+author: >
+  Peter Hunt (Red Hat)
+---
+
+Historically, configuring the correct cgroup driver has been a pain point for users running new
+Kubernetes clusters. On Linux systems, there are two different cgroup drivers:
+`cgroupfs` and `systemd`. In the past, both the [kubelet](/docs/reference/command-line-tools-reference/kubelet/)
+and CRI implementation (like CRI-O or containerd) needed to be configured to use
+the same cgroup driver, or else the kubelet would exit with an error. This was a
+source of headaches for many cluster admins. However, there is light at the end of the tunnel!
+
+## Automated cgroup driver detection
+
+In v1.28.0, the SIG Node community introduced the feature gate
+`KubeletCgroupDriverFromCRI`, which instructs the kubelet to ask the CRI
+implementation which cgroup driver to use. A few minor releases of Kubernetes
+happened whilst we waited for support to land in the major two CRI implementations
+(containerd and CRI-O), but as of v1.31.0, this feature is now beta!
+
+In addition to setting the feature gate, a cluster admin needs to ensure their
+CRI implementation is new enough:
+
+- containerd: Support was added in v2.0.0
+- CRI-O: Support was added in v1.28.0
+
+Then, they should ensure their CRI implementation is configured to the
+cgroup_driver they would like to use.
+
+## Future work
+
+Eventually, support for the kubelet's `cgroupDriver` configuration field will be
+dropped, and the kubelet will fail to start if the CRI implementation isn't new
+enough to have support for this feature.