Adding Windows worker nodes

This page explains how to add Windows worker nodes to a kubeadm cluster.

Before you begin

• A running Windows Server 2022 (or higher) instance with administrative access.
• A running kubeadm cluster created by kubeadm init and following the steps in the document Creating a cluster with kubeadm.

Adding Windows worker nodes

Do the following for each machine:

1. Open a PowerShell session on the machine.
2. Make sure you are Administrator or a privileged user.

Then proceed with the steps outlined below.

Install containerd

To install containerd, first run the following command:

curl.exe -LO https://raw.githubusercontent.com/kubernetes-sigs/sig-windows-tools/master/hostprocess/Install-Containerd.ps1

Then run the following command, but first replace CONTAINERD_VERSION with a recent release from the containerd repository. The version must not have a v prefix. For example, use 1.7.22 instead of v1.7.22:

.\Install-Containerd.ps1 -ContainerDVersion CONTAINERD_VERSION

• Adjust any other parameters for Install-Containerd.ps1 such as netAdapterName as you need them.
• Set skipHypervisorSupportCheck if your machine does not support Hyper-V and cannot host Hyper-V isolated containers.
• If you change the Install-Containerd.ps1 optional parameters CNIBinPath and/or CNIConfigPath you will need to configure the installed Windows CNI plugin with matching values.

Install kubeadm and kubelet

Run the following commands to install kubeadm and the kubelet:

curl.exe -LO https://raw.githubusercontent.com/kubernetes-sigs/sig-windows-tools/master/hostprocess/PrepareNode.ps1
.\PrepareNode.ps1 -KubernetesVersion v1.35.0

• Adjust the parameter KubernetesVersion of PrepareNode.ps1 if needed.

Run kubeadm join

Run the command that was output by kubeadm init. For example:

kubeadm join --token <token> <control-plane-host>:<control-plane-port> --discovery-token-ca-cert-hash sha256:<hash>

Additional information about kubeadm join

If you do not have the token, you can get it by running the following command on the control plane node:

# Run this on a control plane node
sudo kubeadm token list

The output is similar to this:

TOKEN                    TTL  EXPIRES              USAGES           DESCRIPTION            EXTRA GROUPS
8ewj1p.9r9hcjoqgajrj4gi  23h  2018-06-12T02:51:28Z authentication,  The default bootstrap  system:
                                                   signing          token generated by     bootstrappers:
                                                                    'kubeadm init'.        kubeadm:
                                                                                           default-node-token

By default, node join tokens expire after 24 hours. If you are joining a node to the cluster after the current token has expired, you can create a new token by running the following command on the control plane node:

# Run this on a control plane node
sudo kubeadm token create

The output is similar to this:

5didvk.d09sbcov8ph2amjw

If you don't have the value of --discovery-token-ca-cert-hash, you can get it by running the following commands on the control plane node:

sudo cat /etc/kubernetes/pki/ca.crt | openssl x509 -pubkey  | openssl rsa -pubin -outform der 2>/dev/null | \
   openssl dgst -sha256 -hex | sed 's/^.* //'

The output is similar to:

8cb2de97839780a412b93877f8507ad6c94f73add17d5d7058e91741c9d5ec78

The output of the kubeadm join command should look something like:

[preflight] Running pre-flight checks

... (log output of join workflow) ...

Node join complete:
* Certificate signing request sent to control-plane and response
  received.
* Kubelet informed of new secure connection details.

Run 'kubectl get nodes' on control-plane to see this machine join.

A few seconds later, you should notice this node in the output from kubectl get nodes. (for example, run kubectl on a control plane node).

Network configuration

CNI setup on clusters mixed with Linux and Windows nodes requires more steps than just running kubectl apply on a manifest file. Additionally, the CNI plugin running on control plane nodes must be prepared to support the CNI plugin running on Windows worker nodes.

Only a few CNI plugins currently support Windows. Below you can find individual setup instructions for them:

• Flannel
• Calico

Install kubectl for Windows (optional)

See Install and Set Up kubectl on Windows.

What's next

• See how to add Linux worker nodes.