* request a client certificate from the API server during the boot cycle and pause
    * waiting for the request to be satisfied. It will continually refresh the certificate
    * as the certificates expiration approaches.

    * request a client certificate from the API server during the boot cycle and pause
    * waiting for the request to be satisfied. It will continually refresh the certificate
    * as the certificates expiration approaches.

  be removed in a future release) and added a new flag ''--output" that serves the
  same purpose. Affected commands are - "kubeadm config images list", "kubeadm token
  list", "kubeadm upgrade plan", "kubeadm certs check-expiration".' ([#124393](https://github.com/kubernetes/kubernetes/pull/124393), [@carlory](https://github.com/carlory)) [SIG Cluster Lifecycle]
- ACTION REQUIRED for custom scheduler plugin developers:

- Kubelets configured to rotate client certificates now publish a `certificate_manager_server_ttl_seconds` gauge metric indicating the remaining seconds until certificate expiration. ([#91148](https://github.com/kubernetes/kubernetes/pull/91148), [@liggitt](https://github.com/liggitt)) [SIG Auth and Node]

Pero está firmado. Así que, cuando recibes un token que has emitido, puedes verificar que realmente lo emitiste.

De esta manera, puedes crear un token con una expiración de, digamos, 1 semana. Y luego, cuando el usuario regresa al día siguiente con el token, sabes que el usuario todavía está registrado en tu sistema.

    * kubeadm: use the default kubeconfig (/etc/kubernetes/admin.conf) for "kubeadm reset" and "kubeadm upgrade" commands.
* Increase api server client certificate expiration histogram resolution to accommodate short-lived (< 6h) client certificates. ([#74806](https://github.com/kubernetes/kubernetes/pull/74806), [@mxinden](https://github.com/mxinden))

  * Renamed Kubelet metric certificate_manager_server_expiration_seconds to certificate_manager_server_ttl_seconds and changed to report the second until expiration at read time rather than absolute time of expiry. 
  * Improved accuracy of Kubelet metric rest_client_exec_plugin_ttl_seconds.

- The commands `kubeadm certs renew` and `kubeadm certs check-expiration` now honor the `cert-dir` flag on a running Kubernetes cluster. ([#110709](https://github.com/kubernetes/kubernetes/pull/110709), [@chendave](https://github.com/chendave))

- Kubeadm: fix panic in the command "kubeadm certs check-expiration" when "/etc/kubernetes/pki" exists but cannot be read. ([#124124](https://github.com/kubernetes/kubernetes/pull/124124), [@carlory](https://github.com/carlory)) [SIG Cluster Lifecycle]

- Kubeadm: fix panic in the command "kubeadm certs check-expiration" when "/etc/kubernetes/pki" exists but cannot be read. ([#124124](https://github.com/kubernetes/kubernetes/pull/124124), [@carlory](https://github.com/carlory)) [SIG Cluster Lifecycle]