How to upgrade the snap

Upgrading the Kubernetes version of a node is a critical operation that requires careful planning and execution. Canonical Kubernetes is shipped as a snap, which simplifies the upgrade process. This how-to guide will cover the steps to upgrade the Canonical Kubernetes snap and how to put a hold on upgrades if desired.

Important considerations before upgrading

  • According to the upstream Kubernetes, skipping minor versions while upgrading is not supported. For more details, please visit the Version Skew Policy.

  • Before performing an upgrade, it’s important to back up the cluster data. This can be done by following the steps outlined in the backup guide.

  • For more information on managing snap updates, please refer to the snap documentation.

Patch upgrade

Patch upgrades address bug fixes and are typically safe, introducing no breaking changes. Snaps automatically check for updates of their specific track (e.g. 1.32-classic) several times a day and apply them when available. These updates ensure that the latest changes in the installed track are applied. Patch upgrades can also be triggered manually by following the steps below.

  1. List available revisions:

snap info k8s

  1. Refresh the snap:

snap refresh k8s

  1. Verify the upgrade:

Ensure that the upgrade was successful by checking the version of the snap and confirming that the cluster is ready:

snap info k8s
sudo k8s status --wait-ready

Minor version upgrade

Minor versions add new features or deprecate existing features without breaking changes. To upgrade to a new minor version, the snap channel needs to be changed.

  1. List available channels:

snap info k8s

  1. Change the snap channel:

The Canonical Kubernetes snap channel can be changed by using the snap refresh command.

snap refresh --channel=1.33/stable k8s

  1. Verify the upgrade:

Ensure that the upgrade was successful by checking the version of the snap and confirming that the cluster is ready:

snap info k8s
sudo k8s status --wait-ready

Note

In a multi-node cluster, the upgrade should be performed on all nodes.

Freeze upgrades

To prevent automatic updates, the snap can be tied to a specific revision. snap refresh --hold[=<duration>] holds snap refreshes for a specified duration (or forever, if no value is specified).

snap refresh k8s --hold

Or specify a time window:

snap refresh k8s --hold=24h