- kubeadm: `kubeadm upgrade plan` now supports `--etcd-upgrade` flag to control whether the etcd upgrade plan should be displayed. Add an `EtcdUpgrade` field into `UpgradeConfiguration.Plan` for v1beta4. ([#130023](https://github.com/kubernetes/kubernetes/pull/130023), [@SataQiu](https://github.com/SataQiu)) [SIG Cluster Lifecycle]

release.  A new alpha feature is introduced to improve the mechanism that nodes heartbeat back to the control plane.  The `NodeLease` feature results in the node using a `Lease` resource in the `kube-node-lease` namespace that is renewed periodically.  The `NodeStatus` that was used previously to heartbeat back to the control plane is only updated when it changes.  This reduces load on the control plane for large clusters. The Kubelet plugin registration mechanism, which enables automatic discovery of external...

It could be used to tell kubeadm to wait for all control plane components to be ready when running "kubeadm init" or "kubeadm join --control-plane". Previously, kubeadm only waited for the kube-apiserver. The "kubeadm join" workflow now includes a new experimental phase called "wait-control-plane". This phase was marked as non-experimental when WaitForAllControlPlaneComponents became GA. Accordingly, a "kubeadm init" phase "wait-control-plane" was also available once WaitForAllControlPlaneComponents...

(N-3). This aligns with the recent change made by SIG Architecture that extends the support skew between the control plane and kubelets. Tolerate this new kubelet skew for the commands `init`, `join` and `upgrade`. Note that if the `kubeadm` user applies a control plane version that is older than the `kubeadm` version (N-1 maximum) then the skew between the kubelet and control plane would become a maximum of N-2. ([#120825](https://github.com/kubernetes/kubernetes/pull/120825), [@pacoxu](https://github.com/pacoxu))...

Kubeadm: Automate certificate copy between control planes in HA setups

- Joining control plane nodes to a HA cluster can now be simplified by enabling the optional automatic copy of certificates from an existing control plane node.
- You can now use `kubeadm init --experimental-upload-certs` and `kubeadm join --experimental-control-plane --certificate-key`.
kubernetes/kubeadm: [#1373](https://github.com/kubernetes/kubeadm/issues/1373)

- HA improvements:
  - `kubeadm join --experimental-control-plane` can now be used to join control plane instances to an existing cluster.
  - `kubeadm upgrade node experimental-control-plane` can now be used for upgrading secondary control plane instances created with `kubeadm join --experimental-control-plane`.
Multi-arch support (EXPERIMENTAL):

ControlPlaneKubeletLocalMode feature gate. It can be used to tell kubeadm to use the local kube-apiserver endpoint for the kubelet when creating a cluster with "kubeadm init" or when joining control plane nodes with "kubeadm join".  The "kubeadm join" workflow now includes two new experimental phases called "control-plane-join-etcd" and "kubelet-wait-bootstrap" which will be used when the feature gate is enabled. This phases will be marked as non-experimental when ControlPlaneKubeletLocalMode becomes GA. During...

### Deploy a more secure control plane with kubeadm

A new alpha feature allows running the kubeadm control plane components as non-root users. This is a long requested security measure in kubeadm. To try it you must enable the kubeadm-specific `RootlessControlPlane` feature gate. When you deploy a cluster using this alpha feature, your control plane runs with lower privileges.

  - Please adapt your tooling built on top of kubeadm to use the "node-role.kubernetes.io/control-plane" label.
  - The taint applied to control-plane nodes "node-role.kubernetes.io/master:NoSchedule" is now deprecated and will be removed in a future release after a GA deprecation period.

  - The `kubeadm upgrade node config` and `kubeadm upgrade node experimental-control-plane` commands are deprecated in favor of `kubeadm upgrade node`, and will be removed in a future release. ([#78408](https://github.com/kubernetes/kubernetes/pull/78408), [@fabriziopandini](https://github.com/fabriziopandini))