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Chapter 2. Release notes
You can review the following release notes to learn about changes in the Windows Machine Config Operator (WMCO) version 10.18.2.
Issued: 11 March 2026
You can review the following release notes to learn about the bug fixes provided in this release of the Windows Machine Config Operator (WMCO).
The components of the WMCO 10.18.2 were released in RHBA-2026:4395.
2.1.1.1. Bug fixes
-
Before this update, the
hybridOverlayservice was not using the trusted CA bundle when connecting to Kubernetes, because the--k8s-cacertoption was missing from the service command. Because of this, users could encounter trust issues or failures when thehybridOverlayservice attempted to communicate securely with Kubernetes clusters using custom or internal CAs. With this release, thehybridOverlayservice command now includes the--k8s-cacert flagpointing to the trusted CA bundle. As a result, thehybridOverlayservice uses the trusted CA bundle for secure communication, preventing trust issues and ensuring compatibility with the cluster. (OCPBUGS-65856) - Before this update, if you made a configuration change that required the WMCO to delete and re-create an internal config map, such as changing the proxy settings of the cluster, the WMCO pod panicked and entered a crash loop due to a nil pointer dereference panic. With this release, the error handling logic is reworked. As a result, the WMCO pod no longer crashes when an internal config map is recreated. (OCPBUGS-61743)
- Before this update, Windows Server 2019 machines might not have a running SSH server because of network instability. As a result, the WMCO could not access some VMs to complete configuration. With this release, the WMCO makes multiple attempt to SSH into the VM. As such, SSH connectivity to VMs is restored, ensuring smooth configuration and management of nodes. (OCPBUGS-60774)
You can review the following release notes to learn about changes in previous versions of the Custom Metrics Autoscaler Operator.
For the current version, see Red Hat OpenShift support for Windows Containers release notes.
Issued: 27 May 2025
You can review the following release notes to learn about the bug fixes provided in this release of the Windows Machine Config Operator (WMCO).
The components of the WMCO 10.18.1 were released in RHSA-2025:8224.
2.2.1.1. Bug fixes
-
Before this update, Windows nodes were unable to pull from image mirror registries if an organization name or namespace was included in the source of the
ImageTagMirrorSet(ITMS) object. With this release, you can include an organization name or namespace in theITMSobject. With this change, additional guidelines and requirements around using mirror registries have been added to the OpenShift Container Platform documentation. (OCPBUGS-55787)
Issued: 19 March 2025
You can review the following release notes to learn about the bug fixes provided in this release of the Windows Machine Config Operator (WMCO).
The components of the WMCO 10.18.0 were released in RHBA-2025:3040.
2.2.2.1. New features and improvements
- Horizontal Pod autoscaling is available for Windows workloads
- You can now use a horizontal pod autoscaler (HPA) to scale your Windows pods based on CPU and/or memory resource metrics. For more information on using an HPA, see Automatically scaling pods with the horizontal pod autoscaler.
- Control Plane Only updates are now available for Windows nodes
- You can now use Control Plane Only updates, previously known as EUS-to-EUS updates, to update your Windows nodes between OpenShift Container Platform EUS versions. For more information, see Windows Machine Config Operator Control Plane Only upgrade.
- WMCO metrics endpoint is now HTTPS
- The WMCO metrics endpoint is now exposed over HTTPS. Previously, WMCO pod metrics were available over HTTP. This change improves the security posture of the WMCO metrics endpoint.
- WMCO now defaults to info-level logging
-
The WMCO is configured to use the
infolog level by default. You can change the log level todebugby editing the WMCO subscription object. For more information, see Configuring debug-level logging for the Windows Machine Config Operator. - Kubernetes upgrade
- The WMCO now uses Kubernetes 1.31.
2.2.2.2. Bug fixes
-
Before this update, if you installed the WMCO into the the default
openshift-windows-machine-config-operatornamespace and removed the WMCO, subsequently installing the WMCO into a namespace other than the default would fail. This was because the role-based access control (RBAC) for the Windows Instance Config Daemon (WICD) was always associated with the default namespace. With this release, when installing the WMCO to a non-default namespace, the RBAC for the WICD is configured correctly. (OCPBUGS-46473) - Before this update, the OpenShift Container Platform documentation lacked information about WMCO support for the installer-provisioned infrastructure and the user-provisioned infrastructure installation methods. With this release, the documentation now reports that the installer-provisioned infrastructure method is the preferred installation method and can be used with all platforms. The user-provisioned infrastructure method is limited to specific use cases. For more information, see WMCO supported installation method. (OCPBUGS-18898)
2.3. 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 (WMCO). See the vSphere documentation for any information that is relevant to only that platform.
2.3.1. WMCO supported installation method
The WMCO fully supports installing Windows nodes into installer-provisioned infrastructure clusters. This is the preferred OpenShift Container Platform installation method.
For user-provisioned infrastructure (UPI) clusters, the WMCO supports installing Windows nodes only into a UPI cluster installed with the platform: none field set in the install-config.yaml file (bare-metal or provider-agnostic) and only for the BYOH (Bring Your Own Host) use case. UPI is not supported for any other platform.
The following table lists the Windows Server versions that are supported by WMCO 10.18.0, 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) |
|
| Microsoft Azure |
|
| VMware vSphere | Windows Server 2022, OS Build 20348.681 or later |
| Google Cloud | Windows Server 2022, OS Build 20348.681 or later |
| Nutanix | Windows Server 2022, OS Build 20348.681 or later |
| Bare metal or provider agnostic |
|
- For disconnected clusters, the Windows AMI must have the EC2LaunchV2 agent version 2.0.1643 or later installed. For more information, see the Install the latest version of EC2Launch v2 in the AWS documentation.
2.3.3. 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.
- The WMCO does not support OVN-Kubernetes without hybrid networking or OpenShift SDN.
- Dual NIC is not supported on WMCO-managed Windows instances.
| 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 |
| Google Cloud | Hybrid networking with OVN-Kubernetes |
| Nutanix | Hybrid networking with OVN-Kubernetes |
| Bare metal or provider agnostic | Hybrid networking with OVN-Kubernetes |
2.4. Windows Machine Config Operator known limitations
Note the following limitations when working with Windows nodes managed by the WMCO (Windows nodes):
The following OpenShift Container Platform features are not supported on Windows nodes:
- Image builds
- OpenShift Pipelines
- OpenShift Service Mesh
- OpenShift monitoring of user-defined projects
- OpenShift Serverless
- Vertical Pod Autoscaling
- Hosted Control Planes
The following Red Hat features are not supported on Windows nodes:
- Dual NIC is not supported on WMCO-managed Windows instances.
- Windows nodes do not support workloads created by using deployment configs. You can use a deployment or other method to deploy workloads.
- Red Hat OpenShift support for Windows Containers does not support adding Windows nodes to a cluster through a trunk port. The only supported networking configuration for adding Windows nodes is through an access port that carries traffic for the VLAN.
- Red Hat OpenShift support for Windows Containers does not support any Windows operating system language other than English (United States).
-
Due to a limitation within the Windows operating system,
clusterNetworkCIDR addresses of class E, such as240.0.0.0, are not compatible with Windows nodes. 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.
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