- Added `kubeadm alpha certs certificate-key` command to generate secure random key to use on `kubeadm init --experimental-upload-certs` ([#77848](https://github.com/kubernetes/kubernetes/pull/77848), [@yagonobre](https://github.com/yagonobre))

### **Scheduling**

*   Taint key `unreachable` is now in GA.
*   Taint key `notReady` is changed to `not-ready`, and is also now in GA.
*   These changes are automatically updated for taints. Tolerations for these taints must be updated manually. Specifically, you must:

`client-certificate: /var/lib/kubelet/pki/kubelet-client-current.pem` and `client-key: /var/lib/kubelet/pki/kubelet-client-current.pem`, replacing the embedded client certificate and key. ([#84118](https://github.com/kubernetes/kubernetes/pull/84118), [@neolit123](https://github.com/neolit123))
#### Network

- 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...

- kube-controller-manager currently needs a writable `--cert-dir` (default is `/var/run/kubernetes`) for generating self-signed certificates, when no `--tls-cert-file` or `--tls-private-key-file` are provided.
- The `system:kube-controller-manager` ClusterRole lacks permission to `get` the `configmap` extension-apiserver-authentication. kube-controller-manager errors if run with a service account bound to the clusterrole.

  <mime-type type="application/x-x509-key">
  </mime-type>
  <mime-type type="application/x-x509-key;format=pem">
    <sub-class-of type="application/x-x509-key"/>
    <magic priority="50">
      <match value="-----BEGIN PRIVATE KEY-----" type="string" offset="0"/>
      <match value="-----BEGIN PUBLIC KEY-----" type="string" offset="0"/>
      <match value="-----BEGIN KEY-----" type="string" offset="0"/>

    * --docker_only
    * --docker-tls
    * --docker-tls-ca
    * --docker-tls-cert
    * --docker-tls-key
    * --enable_load_reader
    * --event_storage_age_limit
    * --event_storage_event_limit
    * --global_housekeeping_interval
    * --google-json-key
    * --log_cadvisor_usage
    * --machine_id_file
    * --storage_driver_user
    * --storage_driver_password

### SIG Node

SIG-Node advanced several features and made incremental improvements in a few key topic areas this release.

- The CSR signing cert/key pairs will be reloaded from disk like the kube-apiserver cert/key pairs ([#86816](https://github.com/kubernetes/kubernetes/pull/86816), [@deads2k](https://github.com/deads2k)) [SIG API Machinery, Apps and Auth]

- kube-controller-manager
  - The deprecated `--insecure-experimental-approve-all-kubelet-csrs-for-group` flag has been removed.
- kubelet
  - The deprecated `--google-json-key` flag has been removed. Remove the `--google-json-key` flag from kubelet invocations before upgrading. ([#69354](https://github.com/kubernetes/kubernetes/pull/69354), [@yujuhong](https://github.com/yujuhong))