- Kubeadm:  'kubeadm alpha kubelet config download' has been removed, please use 'kubeadm upgrade node phase kubelet-config' instead ([#87944](https://github.com/kubernetes/kubernetes/pull/87944), [@SataQiu](https://github.com/SataQiu)) [SIG Cluster Lifecycle]

- Kubelet config file will be backed up to `/etc/kubernetes/tmp/` folder with `kubeadm-kubelet-config` append with a random suffix as the filename ([#114695](https://github.com/kubernetes/kubernetes/pull/114695), [@chendave](https://github.com/chendave)) [SIG Cluster Lifecycle]

- Add flag --lease-max-object-size and metric etcd_lease_object_counts for kube-apiserver to config and observe max objects attached to a single etcd lease. ([#97480](https://github.com/kubernetes/kubernetes/pull/97480), [@lingsamuel](https://github.com/lingsamuel)) [SIG API Machinery, Instrumentation and Scalability]

## Changelog since v1.8.14

### Action Required

* ACTION REQUIRED: Kubernetes JSON deserializer is now case-sensitive to restore compatibility with pre-1.8 servers. If your config files contains fields with wrong case, the config files will be now invalid. ([#65410](https://github.com/kubernetes/kubernetes/pull/65410), [@nikhita](https://github.com/nikhita))

### Other notable changes

- Kubeadm: Allow manually upgraded component configs to be supplied in a YAML file via the --config option during upgrade plan & apply. The old behavior of --config in which kubeadm configuration and component configs that overwrite...

- The legacy scheduler policy config is removed in v1.23, the associated flags `policy-config-file`, `policy-configmap`, `policy-configmap-namespace` and `use-legacy-policy-config` are also removed. Migrate to Component Config instead, see https://kubernetes.io/docs/reference/scheduling/config/ for details. ([#105424](https://github.com/kubernetes/kubernetes/pull/105424), [@kerthcet](https://github.com/kerthcet))...

    * Added --config-map and --config-map-namespace command line options.
    * If --config-map is set, kube-dns will load dynamic configuration from the config map
      referenced by --config-map-namespace, --config-map. The config-map supports
      the following properties: "federations".
    * --federations flag is now deprecated. Prefer to set federations via the config-map.

feature by default. This implies that 1) for new clusters kubeadm will start using the `kube-system/kubelet-config` naming scheme for the kubelet ConfigMap and RBAC rules, instead of the legacy `kubelet-config-x.yy` naming. 2) during upgrade, kubeadm will only write the new scheme ConfigMap and RBAC objects. To disable the feature you can pass `UnversionedKubeletConfigMap: false` in the kubeadm config for new clusters. For upgrade on existing clusters you can also override the behavior by patching the...

`init` and `join` it is now recommended that you migrate to configure patches via `{Init|Join}Configuration.patches.directory`. For the time being, these flags can be mixed with `--config`, but that might change in the future. On a command line, the last *patches flag takes precedence over previous flags and the value in config. `kubeadm upgrade --patches` will continue to be the only available option, since `upgrade` does not support a configuration file yet. ([#103063](https://github.com/kubernetes...

kubelet related ConfigMap and RBAC rules are now locked to have a simplified naming `*kubelet-config` instead of the legacy naming `*kubelet-config-x.yy`, where `x.yy` was the version of the control plane. If you have previously used the old naming format with `UnversionedKubeletConfigMap=false`, you must manually copy the config map from `kube-system/kubelet-config-x.yy` to `kube-system/kubelet-config` before upgrading to `v1.25`. ([#110327](https://github.com/kubernetes/kubernetes/pull/110327),...