Adding Windows nodes

You can use Kubernetes to run a mixture of Linux and Windows nodes, so you can mix Pods that run on Linux on with Pods that run on Windows. This page shows how to register Windows nodes to your cluster.

Before you begin

• Obtain a Windows Server 2019 license (or higher) in order to configure the Windows node that hosts Windows containers. If you are using VXLAN/Overlay networking you must have also have KB4489899 installed.

• A Linux-based Kubernetes kubeadm cluster in which you have access to the control plane (see Creating a single control-plane cluster with kubeadm).

Objectives

• Register a Windows node to the cluster
• Configure networking so Pods and Services on Linux and Windows can communicate with each other

Getting Started: Adding a Windows Node to Your Cluster

Networking Configuration

Once you have a Linux-based Kubernetes control-plane node you are ready to choose a networking solution. This guide illustrates using Flannel in VXLAN mode for simplicity.

Configuring Flannel

1. Prepare Kubernetes control plane for Flannel

   Some minor preparation is recommended on the Kubernetes control plane in our cluster. It is recommended to enable bridged IPv4 traffic to iptables chains when using Flannel. The following command must be run on all Linux nodes:

   sudo sysctl net.bridge.bridge-nf-call-iptables=1
   

2. Download & configure Flannel for Linux

   Download the most recent Flannel manifest:

   wget https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml
   

   Modify the net-conf.json section of the flannel manifest in order to set the VNI to 4096 and the Port to 4789. It should look as follows:

   net-conf.json: |
       {
         "Network": "10.244.0.0/16",
         "Backend": {
           "Type": "vxlan",
           "VNI": 4096,
           "Port": 4789
         }
       }
   

   Note: The VNI must be set to 4096 and port 4789 for Flannel on Linux to interoperate with Flannel on Windows. See the VXLAN documentation. for an explanation of these fields.

   Note: To use L2Bridge/Host-gateway mode instead change the value of Type to "host-gw" and omit VNI and Port.

3. Apply the Flannel manifest and validate

   Let's apply the Flannel configuration:

   kubectl apply -f kube-flannel.yml
   

   After a few minutes, you should see all the pods as running if the Flannel pod network was deployed.

   kubectl get pods -n kube-system
   

   The output should include the Linux flannel DaemonSet as running:

   NAMESPACE     NAME                                      READY        STATUS    RESTARTS   AGE
   ...
   kube-system   kube-flannel-ds-54954                     1/1          Running   0          1m
   

4. Add Windows Flannel and kube-proxy DaemonSets

   Now you can add Windows-compatible versions of Flannel and kube-proxy. In order to ensure that you get a compatible version of kube-proxy, you'll need to substitute the tag of the image. The following example shows usage for Kubernetes v1.21.14, but you should adjust the version for your own deployment.

   curl -L https://github.com/kubernetes-sigs/sig-windows-tools/releases/latest/download/kube-proxy.yml | sed 's/VERSION/v1.21.14/g' | kubectl apply -f -
   kubectl apply -f https://github.com/kubernetes-sigs/sig-windows-tools/releases/latest/download/flannel-overlay.yml
   

   Note: If you're using host-gateway use https://github.com/kubernetes-sigs/sig-windows-tools/releases/latest/download/flannel-host-gw.yml instead

   Note:

   If you're using a different interface rather than Ethernet (i.e. "Ethernet0 2") on the Windows nodes, you have to modify the line:

   wins cli process run --path /k/flannel/setup.exe --args "--mode=overlay --interface=Ethernet"
   

   in the flannel-host-gw.yml or flannel-overlay.yml file and specify your interface accordingly.

   # Example
   curl -L https://github.com/kubernetes-sigs/sig-windows-tools/releases/latest/download/flannel-overlay.yml | sed 's/Ethernet/Ethernet0 2/g' | kubectl apply -f -
   

Joining a Windows worker node

Note: All code snippets in Windows sections are to be run in a PowerShell environment with elevated permissions (Administrator) on the Windows worker node.

• Docker EE
• CRI-containerD

Install-WindowsFeature -Name containers

curl.exe -LO https://raw.githubusercontent.com/kubernetes-sigs/sig-windows-tools/master/kubeadm/scripts/PrepareNode.ps1
.\PrepareNode.ps1 -KubernetesVersion v1.21.14

curl.exe -LO https://github.com/kubernetes-sigs/sig-windows-tools/releases/latest/download/Install-Containerd.ps1
.\Install-Containerd.ps1

curl.exe -LO https://raw.githubusercontent.com/kubernetes-sigs/sig-windows-tools/master/kubeadm/scripts/PrepareNode.ps1
.\PrepareNode.ps1 -KubernetesVersion v1.21.14 -ContainerRuntime containerD

Verifying your installation

You should now be able to view the Windows node in your cluster by running:

kubectl get nodes -o wide

If your new node is in the NotReady state it is likely because the flannel image is still downloading. You can check the progress as before by checking on the flannel pods in the kube-system namespace:

kubectl -n kube-system get pods -l app=flannel

Once the flannel Pod is running, your node should enter the Ready state and then be available to handle workloads.

What's next

• Upgrading Windows kubeadm nodes