- Kubeadm: support experimental JSON/YAML output for `kubeadm upgrade plan` with the `--output` flag. ([#108447](https://github.com/kubernetes/kubernetes/pull/108447), [@pacoxu](https://github.com/pacoxu))

- Kubeadm: apply `second stage` of the plan to migrate kubeadm away from the usage of the word `master` in labels and taints. For new clusters, the label `node-role.kubernetes.io/master` will no longer be added to control plane nodes, only the label `node-role.kubernetes.io/control-plane` will...

- Kubeadm now prints all the kubelets and nodes that need to be upgraded when running "upgrade plan".
   ([#123578](https://github.com/kubernetes/kubernetes/pull/123578), [@carlory](https://github.com/carlory))

    * pillar['federations_domain_map']...

* Support both JSON and YAML for scheduler configuration. ([#75857](https://github.com/kubernetes/kubernetes/pull/75857), [@danielqsj](https://github.com/danielqsj))
* kubeadm: fix "upgrade plan" not defaulting to a "stable" version if no version argument is passed ([#75900](https://github.com/kubernetes/kubernetes/pull/75900), [@neolit123](https://github.com/neolit123))

### Internal Storage Layer
* **[stable]** The internal storage layer for kubernetes cluster state has been updated to use etcd v3 by default. Existing clusters will have to plan for a data migration window. ([docs](https://kubernetes.io/docs/tasks/administer-cluster/upgrade-1-6/))([kubernetes/features#44](https://github.com/kubernetes/enhancements/issues/44))

### kubeadm

### (No, really, you MUST read this before you upgrade)

    * pillar['federations_domain_map']...

* GCE Windows nodes will rely solely on kubernetes and kube-proxy (and not the GCE agent) for network address management. ([#75855](https://github.com/kubernetes/kubernetes/pull/75855), [@pjh](https://github.com/pjh))
* kubeadm: fix "upgrade plan" not defaulting to a "stable" version if no version argument is passed ([#75900](https://github.com/kubernetes/kubernetes/pull/75900), [@neolit123](https://github.com/neolit123))