- The default Bootstrap Token created with `kubeadm init` v1.8 expires
 and is deleted after 24 hours by default to limit the exposure of the
 valuable credential. You can create a new Bootstrap Token with
 `kubeadm token create` or make the default token permanently valid by specifying
 `--token-ttl 0` to `kubeadm init`. The default token can later be deleted with
 `kubeadm token delete`.

  - This changes the tokens provided to containers at `/var/run/secrets/kubernetes.io/serviceaccount/token` to be time-limited, auto-refreshed, and invalidated when the containing pod is deleted.
  - Clients should reload the token from disk periodically (once per minute is recommended) to ensure they continue to use a valid token. `k8s.io/client-go` version v11.0.0+ and v0.15.0+ reload tokens automatically.

- `kube-controller-manager`: The `LegacyServiceAccountTokenCleanUp` feature gate is now `beta` and enabled by default. When enabled, legacy auto-generated service account token secrets are auto-labeled with a `kubernetes.io/legacy-token-invalid-since` label if the credentials have not been used in the time...

    /** The key of the configuration. e.g. 60 */
    String API_ACCESS_TOKEN_LENGTH = "api.access.token.length";

    /** The key of the configuration. e.g. false */
    String API_ACCESS_TOKEN_REQUIRED = "api.access.token.required";

    /** The key of the configuration. e.g.  */
    String API_ACCESS_TOKEN_REQUEST_PARAMETER = "api.access.token.request.parameter";

    /** The key of the configuration. e.g. Radmin-api */

  // token, and otherwise should reject the token. The audience defaults to the
  // identifier of the apiserver.
  // +optional
  optional string audience = 1;

  // 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

  * All communication is now over TLS
  * Authorization plugins can be installed by kubeadm, including the new default of RBAC
  * The bootstrap token system now allows token management and expiration
* The [`kubefed` federation bootstrap tool](https://kubernetes.io/docs/tutorials/federation/set-up-cluster-federation-kubefed/) has also graduated to beta.

### **Cluster Lifecycle**

*   You must either specify the `--discovery-token-ca-cert-hash` flag to `kubeadm join`, or opt out of the CA pinning feature using `--discovery-token-unsafe-skip-ca-verification`.
*   The default `auto-detect` behavior of the kubelet's `--cloud-provider` flag is removed.

### VMware

- SAML token delegation (required for Zones support in vSphere) is now supported ([#78876](https://github.com/kubernetes/kubernetes/pull/78876), [@dougm](https://github.com/dougm))
- vSphere SAML token auth is now supported when using Zones ([#75515](https://github.com/kubernetes/kubernetes/pull/75515), [@dougm](https://github.com/dougm))

- Upon receiving a LIST request with an expired continue token, the apiserver now returns a continue token together with the 410 "the from parameter is too old" error. If the client does not care about getting a list from a consistent snapshot, the client can use this token to continue listing from the next key, but the returned chunk will be from the latest snapshot. ([#67284](https://github.com/kubernetes/kubernetes/pull/67284),...

* `--service-account-lookup` now defaults to true, requiring the Secret API object containing the token to exist in order for a service account token to be valid. This enables service account tokens to be revoked by deleting the Secret object containing the token. ([#44071](https://github.com/kubernetes/kubernetes/pull/44071), [@liggitt](https://github.com/liggitt))