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About Red Hat OpenShift support for Windows Containers

Windows Container Support for Red Hat OpenShift enables running Windows compute nodes in an OKD cluster. Running Windows workloads is possible by using the Red Hat Windows Machine Config Operator (WMCO) to install and manage Windows nodes. With Windows nodes available, you can run Windows container workloads in OKD.

The release notes for Red Hat OpenShift for Windows Containers tracks the development of the WMCO, which provides all Windows container workload capabilities in OKD.

Release notes for Red Hat Windows Machine Config Operator 6.0.0

This release of the WMCO provides bug fixes for running Windows compute nodes in an OKD cluster. The components of the WMCO 6.0.0 were released in RHBA-2022:6129.

Windows Server 2019 is not supported in vSphere.

Bug fixes

  • Previously, a Windows instance could not be unconfigured when the node’s external IP was present without a pointer record (PTR). As a result, the node’s external IP address without reverse lookup records was used to associate the Windows instance. With this release, a Windows instance can be unconfigured when the node’s external IP address is present without a PTR . (BZ#2070892)

Known issues

  • Windows nodes do not support pulling container images from secure private registries. Use images from public registries or pre-pull the images in the VM image.

Deprecated features

  • Windows Server 20H2 is no longer supported for vSphere worker nodes.

New features and improvements

Windows node certificates are updated

With this release, the WMCO updates the Windows node certificates when the kubelet client certificate authority (CA) certificate is rotated.

Containerd is the default container runtime

Because the Docker runtime is deprecated in Kubernetes 1.24, containerd is now the default runtime for WMCO-supported Windows nodes. Upon the installation of or an upgrade to WMCO 6.0.0, containerd is installed as a Windows service. The kubelet now uses containerd for image pulls instead of the Docker runtime. Users no longer need to enable the Docker-formatted container runtime or install the Docker container runtime on Bring-Your-Own-Host (BYOH) instances. You can continue to use nodes based on VM images that use Docker. The containerd runtime can run along with the Docker service.

The WMCO supports a Windows golden image with or without Docker for vSphere and BYOH Windows instances.

Windows Machine Config Operator prerequisites

The following information details the supported platform versions, Windows Server versions, and networking configurations for the Windows Machine Config Operator. See the vSphere documentation for any information that is relevant to only that platform.

WMCO 6.0.0 supported platforms and Windows Server versions

The following table lists the Windows Server versions that are supported by WMCO 6.0.0, based on the applicable platform. Windows Server versions not listed are not supported and attempting to use them will cause errors. To prevent these errors, use only an appropriate version for your platform.

Platform Supported Windows Server version

Amazon Web Services (AWS)

Windows Server 2019, version 1809 Long-Term Servicing Channel (LTSC)

Microsoft Azure

  • Windows Server 2022 Long-Term Servicing Channel (LTSC). OS Build 20348.681 or later.

  • Windows Server 2019, version 1809 Long-Term Servicing Channel (LTSC)

VMware vSphere

Windows Server 2022 Long-Term Servicing Channel (LTSC). OS Build 20348.681 or later.

Bare metal or provider agnostic

Windows Server 2022 Long-Term Servicing Channel (LTSC). OS Build 20348.681 or later.

Supported networking

Hybrid networking with OVN-Kubernetes is the only supported networking configuration. See the additional resources below for more information on this functionality. The following tables outline the type of networking configuration and Windows Server versions to use based on your platform. You must specify the network configuration when you install the cluster. Be aware that OpenShift SDN networking is the default network for OKD clusters. However, OpenShift SDN is not supported by WMCO.

Table 1. Platform networking support
Platform Supported networking

Amazon Web Services (AWS)

Hybrid networking with OVN-Kubernetes

Microsoft Azure

Hybrid networking with OVN-Kubernetes

VMware vSphere

Hybrid networking with OVN-Kubernetes with a custom VXLAN port

Bare metal or provider agnostic

Hybrid networking with OVN-Kubernetes

Table 2. Hybrid OVN-Kubernetes Windows Server support
Hybrid networking with OVN-Kubernetes Supported Windows Server version

Default VXLAN port

  • Windows Server 2022 Long-Term Servicing Channel (LTSC)

  • Windows Server 2019, version 1809 Long-Term Servicing Channel (LTSC)

Custom VXLAN port

Windows Server 2022 Long-Term Servicing Channel (LTSC). OS Build 20348.681 or later.

Known limitations

Note the following limitations when working with Windows nodes managed by the WMCO (Windows nodes):

  • The following OKD features are not supported on Windows nodes:

    • Red Hat OpenShift Developer CLI (odo)

    • Image builds

    • OpenShift Pipelines

    • OpenShift Service Mesh

    • OpenShift monitoring of user-defined projects

    • OpenShift Serverless

  • The following Red Hat features are not supported on Windows nodes:

  • Windows nodes do not support pulling container images from private registries. You can use images from public registries or pre-pull the images.

  • Windows nodes do not support workloads created by using deployment configs. You can use a deployment or other method to deploy workloads.

  • Windows nodes are not supported in clusters that use a cluster-wide proxy. This is because the WMCO is not able to route traffic through the proxy connection for the workloads.

  • Windows nodes are not supported in clusters that are in a disconnected environment.

  • Red Hat OpenShift support for Windows Containers supports only in-tree storage drivers for all cloud providers.

  • Kubernetes has identified the following node feature limitations :

    • Huge pages are not supported for Windows containers.

    • Privileged containers are not supported for Windows containers.

  • Kubernetes has identified several API compatibility issues.