Red Hat OpenShift support for Windows Containers is a feature providing the ability to run Windows compute nodes in an OKD cluster. This 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 support for Windows Containers tracks the development of the WMCO, which provides all Windows container workload capabilities in OKD.
The WMCO 1.0.4 is now available with bug fixes. The components of the WMCO were released in RHBA-2021:1061.
The support statements and known issues documented for the WMCO 1.0.2 release also apply for this release of the WMCO.
Previously, if you had a cluster with two Windows nodes, and you created a web server deployment with two replicas, the pods would each land on a Windows compute node. In this scenario, if you created a
Service object with type
LoadBalancer, communication with the load balancer endpoint was flaky. To mitigate this issue, you were required to use Windows Server 2019 with a version 10.0.17763.1457 or earlier. This issue has been fixed, and you are no longer restricted to a subset of Windows Server 2019 image versions. (BZ#1942630)
The WMCO 1.0.3 is now available with bug fixes and security updates. The components of the WMCO were released in RHBA-2021:0410.
You must upgrade to WMCO 1.0.3+ before upgrading to WMCO 2.x.
This release of the WMCO provides initial support for running Windows compute nodes in an OKD cluster. The components of the WMCO were released in RHBA-2020:5596.
WMCO supports self-managed clusters built using installer-provisioned infrastructure running on the following cloud providers:
Amazon Web Services (AWS)
The following Windows Server operating systems are supported in the initial release of the WMCO:
Windows Server Long-Term Servicing Channel (LTSC): Windows Server 2019
Running Windows container workloads is not supported for clusters in a restricted network or disconnected environment.
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)
OpenShift Service Mesh
OpenShift monitoring of user-defined projects
Horizontal Pod Autoscaling
Vertical Pod Autoscaling
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.
Pod termination grace periods require the containerd container runtime to be installed on the Windows node.
Kubernetes has identified several API compatibility issues.