cluster.ninja

Upgrade hop

Kubernetes 1.20 → 1.21

1.20End of lifeEOL 28 Feb 2022 1.21End of lifeEOL 28 Jun 2022

1.21 is itself end of life. If you are on 1.20 today, plan the whole path to a supported version (at least 1.35) with the upgrade planner.

1 · Fix removed APIs first

No API versions are removed between 1.20 and 1.21.

2 · Other changes that can bite

Deprecated in 1.21

  • PodSecurityPolicy is deprecated; it stays functional for several releases and is planned for removal in 1.25.
  • The Service topologyKeys field and the alpha features that used it are deprecated in favour of topology-aware hints (alpha).

Our summary of the 1.21 release announcement (CC BY 4.0). Read the full changelog for your components.

3 · Upgrade in this order

  1. Prepare. Move every node to 1.19 or newer if any are older: a 1.21 API server supports kubelets back to 1.19 only. Upgrade to the newest 1.20 patch, 1.20.15.
  2. kube-apiserver to 1.21 (in HA clusters, one instance at a time; old and new may differ by one minor during the roll). Use the newest patch, 1.21.14.
  3. kube-controller-manager, kube-scheduler, cloud-controller-manager to 1.21, once every API server is on 1.21.
  4. kubelet on each node (drain first). Optional in this hop: kubelets from 1.19 to 1.21 all work with a 1.21 control plane.
  5. kube-proxy: no newer than the API server, and within the same window as the kubelet it runs beside.
  6. kubectl: 1.20 to 1.22 all talk to a 1.21 API server.

From the official version skew policy. Managed services run the control-plane steps for you; node pools are still yours to schedule.