certificates directory as `kubelet-client.key` and `kubelet-client.crt`.  Subsequent certificates created by cert rotation were created in a combined PEM file that was atomically rotated as `kubelet-client-DATE.pem` in that directory, which meant clients relying on the `node.kubeconfig` generated by bootstrapping would never use a rotated cert.  The initial bootstrap certificate is now generated into the cert directory as a PEM file and symlinked to `kubelet-client-current.pem` so that the generated kubeconfig...

* kubelet `--cert-dir` now defaults to `/var/lib/kubelet/pki`, in order to ensure bootstrapped and rotated certificates persist beyond a reboot. resolves an issue in kubeadm with false-positive `/var/lib/kubelet is not empty` message during pre-flight checks ([#53317](https://github.com/kubernetes/kubernetes/pull/53317), [@liggitt](https://github.com/liggitt))...

## Changelog since v1.13.1

### Other notable changes

* client-go: shortens refresh period for token files to 1 minute to ensure auto-rotated projected service account tokens are read frequently enough. ([#72437](https://github.com/kubernetes/kubernetes/pull/72437), [@liggitt](https://github.com/liggitt))

- Kubelet: Added kubelet serving certificate metric `server_rotation_seconds` which is a histogram reporting the age of a just rotated serving certificate in seconds. ([#84534](https://github.com/kubernetes/kubernetes/pull/84534), [@sambdavidson](https://github.com/sambdavidson))

  // expirationSeconds is the requested duration of validity of the service
  // account token. As the token approaches expiration, the kubelet volume
  // plugin will proactively rotate the service account token. The kubelet will
  // start trying to rotate the token if the token is older than 80 percent of
  // its time to live or if the token is older than 24 hours.Defaults to 1 hour
  // and must be at least 10 minutes.
  // +optional

- Fixed the bug where kubelet couldn't output logs after log file rotated when `kubectl logs POD_NAME -f` is running. ([#115702](https://github.com/kubernetes/kubernetes/pull/115702), [@xyz-li](https://github.com/xyz-li))

ACL’ed on the pods’ service account without handing out unnecessary permissions to the CSI drivers’ service account. This feature is especially important for secret-handling CSI drivers, such as the secrets-store-csi-driver. Since these tokens can be rotated and short-lived, this feature also provides a knob for CSI drivers to receive `NodePublishVolume` RPC calls periodically with the new token. This knob is also useful when volumes are short-lived, e.g. certificates.

### Introducing Graceful...

- The Kubernetes API server now correctly detects and closes existing TLS connections when its client certificate file for kubelet authentication has been rotated. ([#115315](https://github.com/kubernetes/kubernetes/pull/115315), [@enj](https://github.com/enj)) [SIG API Machinery, Auth, Node and Testing]

* client-go: shortens refresh period for token files to 1 minute to ensure auto-rotated projected service account tokens are read frequently enough. ([#72437](https://github.com/kubernetes/kubernetes/pull/72437), [@liggitt](https://github.com/liggitt))

    - `rest_client_certificate_rotation_age` a histogram reporting the age of a just rotated client certificate in seconds. ([#84382](https://github.com/kubernetes/kubernetes/pull/84382), [@sambdavidson](https://github.com/sambdavidson)) [SIG API Machinery, Auth, Cluster Lifecycle and Instrumentation]