Using the Kubeadm control plane type to manage a control plane provides several ways to upgrade control plane machines.
KCP will generate and manage the admin Kubeconfig for clusters. The client certificate for the admin user is created with a valid lifespan of a year, and will be automatically regenerated when the cluster is reconciled and has less than 6 months of validity remaining.
See the section on upgrading clusters.
See the section on Adopting existing machines into KubeadmControlPlane management