OpenShift Container Platform

Replace a control plane machine

Replace a control plane machine to apply updated configurations or recover from hardware issues while maintaining cluster stability. The control plane machine set replaces the deleted machine with one using the specification in the control plane machine set custom resource (CR).

Prerequisites

If your cluster runs on Red Hat OpenStack Platform (RHOSP) and you need to evacuate a compute server, such as for an upgrade, you must disable the RHOSP compute node that the machine runs on by running the following command:
```
$ openstack compute service set <target_node_host_name> nova-compute --disable
```
For more information, see Preparing to migrate in the RHOSP documentation.

Procedure

List the control plane machines in your cluster by running the following command:

$ oc get machines \
  -l machine.openshift.io/cluster-api-machine-role==master \
  -n openshift-machine-api

Delete a control plane machine by running the following command:

$ oc delete machine \
  -n openshift-machine-api \
  <control_plane_machine_name>

where <control_plane_machine_name> specifies the name of the control plane machine to delete.

If you delete multiple control plane machines, the control plane machine set replaces them according to the configured update strategy:

For clusters that use the default RollingUpdate update strategy, the Operator replaces one machine at a time until each machine is replaced.
For clusters that are configured to use the OnDelete update strategy, the Operator creates all of the required replacement machines simultaneously.

Both strategies maintain etcd health during control plane machine replacement.