- Kubeadm: when adding new control plane nodes with "kubeadm join", ensure that the etcd member addition is performed only if a given member URL does not already exist in the list of members. Similarly, on "kubeadm reset" only remove an etcd member if its ID exists. ([#127620](https://github.com/...

- k8s-dns-node-cache image has been updated to v1.15.1 ([#76640](https://github.com/kubernetes/kubernetes/pull/76640), [@george-angel](https://github.com/george-angel))

### Unchanged

* Etcd health checks by the apiserver now ensure the apiserver can connect to and exercise the etcd API ([#65027](https://github.com/kubernetes/kubernetes/pull/65027), [@liggitt](https://github.com/liggitt))

- Kubeadm: during execution of the "check expiration" command, treat the etcd CA as external if there is a missing etcd CA key file (etcd/ca.key) and perform the proper validation on certificates signed by the etcd CA. Additionally, make sure that the CA for all entries in the output table is included - for both certificates on disk and in kubeconfig files. ([#106924](https://github.com/kube...