kubeadm-upgrade

If you build your cluster with kubeadm, you also have the option to upgrade the cluster using the kubeadm upgrade command. While most choose to remain with a version for as long as possible, and will often skip several releases, this does offer a useful path to regular upgrades for security reasons.

• plan

  This will check the installed version against the newest found in the repository, and verify if the cluster can be upgraded.

• apply

  Upgrades the first control plane node of the cluster to the specified version.

• diff

  Similar to an apply --dry-run, this command will show the differences applied during an upgrade.

• node

  This allows for updating the local kubelet configuration on worker nodes, or the control planes of other cp nodes if there is more than one. Also, it will access a phase command to step through the upgrade process.

General upgrade process:

• Update the software

• Check the software version

• Drain the control plane

• View the planned upgrade

• Apply the upgrade

• Uncordon the control plane to allow pods to be scheduled.

Detailed steps can be found in the Kubernetes documentation: Upgrading kubeadm clusters.