With recent CVEs and customer requests, there is a need to consolidate the methods in which we have to update existing cluster's bootimages. There are scattered documentation around how this can be done but we should create a supported way to do this.

This is not intended to override the feature in 4.15 onwards where we will look to support bootimage updates via the MCO directly. This will continue to work and will form the foundation of non-machineset backed scaling.