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Docker 20.10 and the Kubernetes dockershim Notice

Docker Engine 20.10 was released on 8 December 2020. Kubernetes also announced the deprecation of dockershim.

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  • Docker Engine 20.10
  • Kubernetes 1.20
  • containerd

Docker Engine 20.10 (8 December 2020) brings cgroups v2 support, rootless mode as a supported feature, and docker run --pull. Upgrade a test machine first; the repository package names are unchanged.

docker version
docker info | grep -i "cgroup"

Separately, Kubernetes 1.20 (8 December 2020) announced that the built-in dockershim, which lets the kubelet talk to Docker Engine, is deprecated and planned for removal in a later release.

What this does not mean:

  • Docker-built images keep working. They are standard OCI images that any runtime can run.
  • Your docker build workflow does not change.

What it does mean: clusters should plan to use containerd or CRI-O as the runtime. Check what your nodes use with kubectl get nodes -o wide (see the container runtime column). Avoid depending on the Docker socket from inside pods, since it will not be there on containerd nodes.