How to install custom Canonical Kubernetes on machines

By default, the version field in the machine specifications will determine which Canonical Kubernetes version is downloaded from the stable risk level. This guide walks you through the process of installing Canonical Kubernetes with a specific risk level, revision, or from a local path.

Prerequisites

To follow this guide, you will need:

  • A Kubernetes management cluster with Cluster API and providers installed and configured.

  • A generated cluster spec manifest

Please refer to the getting-started guide for further details on the required setup.

This guide will call the generated cluster spec manifest cluster.yaml.

Using the configuration specification

Canonical Kubernetes can be installed on machines using a specific channel, revision or localPath by specifying the respective field in the spec of the machine.

apiVersion: controlplane.cluster.x-k8s.io/v1beta2
kind: CK8sControlPlane
...
spec:
  ...
  spec:
    channel: 1.xx-classic/candidate
    # Or
    revision: 1234
    # Or
    localPath: /path/to/snap/on/machine

Note that for the localPath to work the snap must be available on the machine at the specified path on boot.

Overwrite the existing install.sh script

Running the install.sh script is one of the steps that cloud-init performs on machines and can be overwritten to install a custom Canonical Kubernetes snap. This can be done by adding a files field to the spec of the machine with a specific path.

apiVersion: controlplane.cluster.x-k8s.io/v1beta2
kind: CK8sControlPlane
...
spec:
  ...
  spec:
    files:
    - content: |
        #!/bin/bash -xe
        snap install k8s --classic --channel=1.32-classic/candidate
      owner: root:root
      path: /capi/scripts/install.sh
      permissions: "0500"

Now the new control plane nodes that are created using this manifest will have the 1.32-classic/candidate Canonical Kubernetes snap installed on them!

Note

Use the configuration specification, if you’re only interested in installing a specific channel, revision, or form the local path.