How to join worker nodes with a custom configuration¶

When creating a Canonical Kubernetes cluster you may need to join a worker node with a configuration that differs from the default. For example, the worker node may need to use alternative certificates for security reasons or the worker node may have specific networking requirements that must be configured at node creation. Passing extra command line arguments or a configuration file at cluster join allows you to modify the configuration of your worker node.

Prerequisites¶

This guide assumes the following:

A working Kubernetes cluster deployed with the k8s snap

Generate worker join token¶

When generating a join token for a worker node, pass the --worker parameter to the get-join-token command. Adding the hostname when creating a worker join token is optional and is not included here.

sudo k8s get-join-token --worker

Install the snap¶

On the new worker machine, install the snap:

sudo snap install k8s --classic --channel=1.33-classic/stable

Join the cluster¶

Default configuration¶

To join the cluster with the default configuration, on the worker node use the token generated from the output of the get-join-token command and run:

sudo k8s join-cluster <JOIN-TOKEN>

Command line arguments¶

To discover the configuration options available as command line arguments when joining the cluster, on the control node run:

sudo k8s join-cluster --help

You can then run the join the cluster with the token generated from the output of the get-join-token command and any arguments you may need. For example, to set the output formatting to JSON run:

sudo k8s join-cluster --output-format=json <JOIN-TOKEN>

Configuration file¶

More configuration options are available when a configuration file is specified. Please consult the reference page for all of the available configuration options and their defaults.

In this example, the configuration file provided at cluster join will set the proxy mode of the worker machine to ipvs.

Create a custom_config.yaml file that sets the intended custom configurations.

cat <<EOF > custom_config.yaml
extra-node-kube-proxy-args:
    "--proxy-mode" : "ipvs"
EOF

On the worker node, join the cluster with the token generated from the output of the get-join-token command and the custom_config.yaml file.

sudo k8s join-cluster --file path/to/custom_config.yaml <JOIN-TOKEN>

Verify worker join¶

After a few moments, the node should have joined the cluster with a success message. Verify the node has joined the cluster by switching to the control node and running:

sudo k8s kubectl get nodes

The output should list the worker node in a Ready state.

Also verify if any custom configuration has been applied to the worker.