As an OpenShift cluster admin, I routinely have to upgrade my cluster to a newer OpenShift release. As part of that process, I want to build my OS image ahead of performing the upgrade to ensure that my customizations will continue to work in the new OS image. To facilitate that, I need both the ability to specify a custom base image pullspec as well as the ability to separate the image build process and the rollout process.

The upgrade process will need to be modified slightly to allow the cluster admin to specify the OS image pullspec prior to beginning the upgrade. Alternatively, if no pullspec is specified, on-cluster builds should be performed as early in the upgrade process as possible.

Done When:

• There is the ability to set the base image used for on-cluster builds. This could be done via an API field on the MachineConfigPool or alternatively, it could be via an annotation.
• Separating the image build process and rollout process is not in scope for this card because of https://issues.redhat.com/browse/MCO-1000. Consequently, this card will depend on the completion of MCO-1000.