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Highly available kubeadm clusters are designed to be upgraded in place. The Kubernetes api-server is also designed to function with a minor version skew (for e

Highly available kubeadm clusters are designed to be upgraded in place. The Kubernetes api-server is also designed to function with a minor version skew (for example v1.19.x and v1.20.x) that would happen during an in-place upgrade. Cluster API takes the above and can in-place upgrade clusters for you. It's pretty awesome to see first hand. Bumping the Kubernetes version string and machine image reference can upgrade and even swap distros of a running cluster with no down-time.

dharmab 5y ago
One caveat is that downgrading the apiserver is not guaranteed to be possible, since the schema of some types in the API may have been migrated to newer versions in the etcd database that the previous version may not be able to read. There are tools such as Velero (https://velero.io https://velero.io) which can restore a previous snapshot, but you will likely incur downtime and lose any changes since the snapshot.