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Guide for adding Windows Nodes in Kubernetes

The Kubernetes platform can now be used to run both Linux and Windows containers. One or more Windows nodes can be registered to a cluster. This guide shows how to:

• Register a Windows node to the cluster
• Configure networking so pods on Linux and Windows can communicate

• Before you begin
• Getting Started: Adding a Windows Node to Your Cluster

Before you begin

• Obtain a Windows Server license in order to run the Windows node that will execute the Windows container. You can use your organization’s licenses for the cluster, or acquire one from Microsoft, a reseller, or via the major cloud providers such as GCP, AWS, and Azure by provisioning a virtual machine running Windows Server through their marketplaces. A time-limited trial is also available.
• Build a Linux-based Kubernetes cluster in which you have access to the control plane (some examples include Getting Started from Scratch, kubeadm, AKS Engine, GCE, AWS).

Getting Started: Adding a Windows Node to Your Cluster

Plan IP Addressing

Kubernetes cluster management requires careful planning of your IP addresses so that you do not inadvertently cause network collision. This guide assumes that you are familiar with the Kubernetes networking concepts.

In order to deploy your cluster you will need the following address spaces:

Review the networking options supported in ‘Intro to Windows containers in Kubernetes: Supported Functionality: Networking’ to determine how you need to allocate IP addresses for your cluster.

Components that run on Windows

While the Kubernetes control plane runs on your Linux node(s), the following components will be configured and run on your Windows node(s).

1. kubelet
2. kube-proxy
3. kubectl (optional)
4. Container runtime

Get the latest binaries from https://github.com/kubernetes/kubernetes/releases, starting with v1.14 or later. The Windows-amd64 binaries for kubeadm, kubectl, kubelet, and kube-proxy can be found under the CHANGELOG link.

Networking Configuration

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

Configuring Flannel in VXLAN mode on the Linux controller

1. Prepare Kubernetes master for Flannel

   Some minor preparation is recommended on the Kubernetes master in our cluster. It is recommended to enable bridged IPv4 traffic to iptables chains when using Flannel. This can be done using the following command:

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

2. Download & configure Flannel

   Download the most recent Flannel manifest:

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

   There are two sections you should modify to enable the vxlan networking backend:

   After applying the steps below, the net-conf.json section of kube-flannel.yml 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. Support for other VNIs is coming soon. See the VXLAN documentation at https://github.com/coreos/flannel/blob/master/Documentation/backends.md#vxlan for an explanation of these fields.
   

3. In the net-conf.json section of your kube-flannel.yml, double-check:

   1. The cluster subnet (e.g. “10.244.0.0/16”) is set as per your IP plan.
      • VNI 4096 is set in the backend
      • Port 4789 is set in the backend
   2. In the cni-conf.json section of your kube-flannel.yml, change the network name to vxlan0.
      
      

   Your cni-conf.json should look as follows:

   cni-conf.json: |
       {
         "name": "vxlan0",
         "plugins": [
           {
             "type": "flannel",
             "delegate": {
               "hairpinMode": true,
               "isDefaultGateway": true
             }
           },
           {
             "type": "portmap",
             "capabilities": {
               "portMappings": true
             }
           }
         ]
       }

4. Apply the Flannel yaml and Validate

   Let’s apply the Flannel configuration:

   kubectl apply -f kube-flannel.yml

   Next, since the Flannel pods are Linux-based, apply a NodeSelector patch, which can be found here, to the Flannel DaemonSet pod:

   kubectl patch ds/kube-flannel-ds-amd64 --patch "$(cat node-selector-patch.yml)" -n=kube-system

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

   kubectl get pods --all-namespaces

   

   Verify that the Flannel DaemonSet has the NodeSelector applied.

   kubectl get ds -n kube-system

   

Join Windows Worker

In this section we’ll cover configuring a Windows node from scratch to join a cluster on-prem. If your cluster is on a cloud you’ll likely want to follow the cloud specific guides in the next section.

Preparing a Windows Node

Note: All code snippets in Windows sections are to be run in a PowerShell environment with elevated permissions (Admin).

1. Install Docker (requires a system reboot)

   Kubernetes uses Docker as its container engine, so we need to install it. You can follow the official Docs instructions, the Docker instructions, or try the following recommended steps:

   Enable-WindowsOptionalFeature -FeatureName Containers
   Restart-Computer -Force
   Install-Module -Name DockerMsftProvider -Repository PSGallery -Force
   Install-Package -Name Docker -ProviderName DockerMsftProvider

   If you are behind a proxy, the following PowerShell environment variables must be defined:

   [Environment]::SetEnvironmentVariable("HTTP_PROXY", "http://proxy.example.com:80/", [EnvironmentVariableTarget]::Machine)
   [Environment]::SetEnvironmentVariable("HTTPS_PROXY", "http://proxy.example.com:443/", [EnvironmentVariableTarget]::Machine)

   If after reboot you see the following error, you need to restart the docker service manually

   

   Start-Service docker

   Note:

   The "pause" (infrastructure) image is hosted on Microsoft Container Registry (MCR). You can access it using "docker pull mcr.microsoft.com/k8s/core/pause:1.0.0". The DOCKERFILE is available at https://github.com/Microsoft/SDN/blob/master/Kubernetes/windows/Dockerfile.
   

2. Prepare a Windows directory for Kubernetes

   Create a “Kubernetes for Windows” directory to store Kubernetes binaries as well as any deployment scripts and config files.

   mkdir c:\k

3. Copy Kubernetes certificate

   Copy the Kubernetes certificate file $HOME/.kube/config from the Linux controller to this new C:\k directory on your Windows node.

   Tip: You can use tools such as xcopy, WinSCP, or this PowerShell wrapper for WinSCP to transfer the config file between nodes.

4. Download Kubernetes binaries

   To be able to run Kubernetes, you first need to download the kubelet and kube-proxy binaries. You download these from the Node Binaries links in the CHANGELOG.md file of the latest releases. For example ‘kubernetes-node-windows-amd64.tar.gz’. You may also optionally download kubectl to run on Windows which you can find under Client Binaries.

   Use the Expand-Archive PowerShell command to extract the archive and place the binaries into C:\k.

Join the Windows node to the Flannel cluster

The Flannel overlay deployment scripts and documentation are available in this repository. The following steps are a simple walkthrough of the more comprehensive instructions available there.

Download the Flannel start.ps1 script, the contents of which should be extracted to C:\k:

cd c:\k
[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
wget https://raw.githubusercontent.com/Microsoft/SDN/master/Kubernetes/flannel/start.ps1 -o c:\k\start.ps1

Note: start.ps1 references install.ps1, which will download additional files such as the flanneld executable and the Dockerfile for infrastructure pod and install those for you. For overlay networking mode, the firewall will be opened for local UDP port 4789. There may be multiple powershell windows being opened/closed as well as a few seconds of network outage while the new external vSwitch for the pod network is being created the first time. Run the script using the arguments as specified below:

.\start.ps1 -ManagementIP <Windows Node IP> -NetworkMode overlay  -ClusterCIDR <Cluster CIDR> -ServiceCIDR <Service CIDR> -KubeDnsServiceIP <Kube-dns Service IP> -LogDir <Log directory>

Now you can view the Windows nodes in your cluster by running the following:

kubectl get nodes

Note: You may want to configure your Windows node components like kubelet and kube-proxy to run as services. View the services and background processes section under troubleshooting for additional instructions. Once you are running the node components as services, collecting logs becomes an important part of troubleshooting. View the gathering logs section of the contributing guide for further instructions.

Public Cloud Providers

Azure

AKS-Engine can deploy a complete, customizable Kubernetes cluster with both Linux & Windows nodes. There is a step-by-step walkthrough available in the docs on GitHub.

GCP

Users can easily deploy a complete Kubernetes cluster on GCE following this step-by-step walkthrough on GitHub

Deployment with kubeadm and cluster API

Kubeadm is becoming the de facto standard for users to deploy a Kubernetes cluster. Windows node support in kubeadm will come in a future release. We are also making investments in cluster API to ensure Windows nodes are properly provisioned.

Next Steps

Now that you’ve configured a Windows worker in your cluster to run Windows containers you may want to add one or more Linux nodes as well to run Linux containers. You are now ready to schedule Windows containers on your cluster.

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