Chapter 8. Windows node updates

When a new version of the Windows Machine Config Operator (WMCO) is released that is compatible with the current cluster version, the Operator is updated based on the update channel and subscription approval strategy it was installed with when using the Operator Lifecycle Manager (OLM). The WMCO update results in the Kubernetes components in the Windows machine being updated.

For a non-disruptive update, the WMCO terminates the Windows machines configured by the previous version of the WMCO and recreates them using the current version. This is done by deleting the Machine object, which results in the drain and deletion of the Windows node. To facilitate an update, the WMCO adds a version annotation to all the configured nodes. During an update, a mismatch in version annotation results in the deletion and recreation of a Windows machine. To have minimal service disruptions during an update, the WMCO only updates one Windows machine at a time.

After the update, it is recommended that you set the spec.os.name.windows parameter in your workload pods. The WMCO uses this field to authoritatively identify the pod operating system for validation and is used to enforce Windows-specific pod security context constraints (SCCs).

OpenShift Container Platform and Windows Machine Config Operator (WMCO) support updating from one EUS version to another EUS version of OpenShift Container Platform, in a process called a Control Plane Only update. After upgrading the cluster, the Windows nodes are updated from the starting EUS version to the new EUS version while keeping the Windows workloads in a healthy state with no disruptions.