`super-admin.conf` to one year if the file exists; if it does not exist a "MISSING" note will be printed. `kubeadm upgrade apply` for this release will migrate this particular node to the two file setup. Subsequent kubeadm releases will continue to optionally renew the certificate in `super-admin.conf` if the file exists on disk and if renew on upgrade is not disabled. `kubeadm join --control-plane` will now generate only an `admin.conf` file that has the less privileged User. ([#121305](https://git...

  * `--basic-auth-file` supports optionally specifying groups in the fourth column of the file ([#39651](https://github.com/kubernetes/kubernetes/pull/39651), [@liggitt](https://github.com/liggitt))

made using the built-in function
<a href="#Making_slices_maps_and_channels"><code>make</code></a>,
which takes a slice type
and parameters specifying the length and optionally the capacity.
A slice created with <code>make</code> always allocates a new, hidden array
to which the returned slice value refers. That is, executing
</p>

<pre>
make([]T, length, capacity)
</pre>

- Both directory and block devices are now supported for local volume plugin FileSystem VolumeMode.  ([#63011](https://github.com/kubernetes/kubernetes/pull/63011), [@NickrenREN](https://github.com/NickrenREN))
- CSI NodePublish call can optionally contain information about the pod that requested the CSI volume. ([#67945](https://github.com/kubernetes/kubernetes/pull/67945), [@jsafrane](https://github.com/jsafrane))

- JWT authenticators specified via the `AuthenticationConfiguration.jwt` array can now optionally specify either the `controlplane` or `cluster` egress selector by setting the `issuer.egressSelectorType` field.  When unset, the prior behavior of using no egress selector is retained.  The StructuredAuthenticationConfigurationEgressSelector beta...

#### Custom Resource Definitions (CRDs)
* [alpha] The CustomResourceDefinition API can now optionally
  [validate custom objects](https://kubernetes.io/docs/tasks/access-kubernetes-api/extend-api-custom-resource-definitions/#validation)
  based on a JSON schema provided in the CRD spec.

	* A new controller for managing DNS records is introduced which can be optionally disabled to enable third party components to manage DNS records for federated services. ([#45034](https://github.com/kubernetes/kubernetes/pull/45034), [@shashidharatd](https://github.com/shashidharatd))

### Promoted Server Side Unknown Field Validation to Beta

- The kube-apiserver's healthz now takes in an optional query parameter which allows you to disable health checks from causing healthz failures.  ([#70676](https://github.com/kubernetes/kubernetes/pull/70676), [@logicalhan](https://github.com/logicalhan))

## Dependencies

### Added
- github.com/antihax/optional: [v1.0.0](https://github.com/antihax/optional/tree/v1.0.0)
- github.com/benbjohnson/clock: [v1.0.3](https://github.com/benbjohnson/clock/tree/v1.0.3)
- github.com/bits-and-blooms/bitset: [v1.2.0](https://github.com/bits-and-blooms/bitset/tree/v1.2.0)