### Immutable Secrets and ConfigMaps

Immutable Secrets and ConfigMaps graduates to GA. This feature allows users to specify that the contents of a particular Secret or ConfigMap is immutable for its object lifetime. For such instances, Kubelet will not watch/poll for changes and therefore reducing apiserver load.

    * `kubectl version` now supports `--output` ([#39858](https://github.com/kubernetes/kubernetes/pull/39858), [@alejandroEsc](https://github.com/alejandroEsc))

    * `kubectl create configmap` has a new option `--from-env-file` that populates a configmap from file which follows a key=val format for each line. ([#38882](https://github.com/kubernetes/kubernetes/pull/38882), [@fraenkel](https://github.com/fraenkel))

* Native support for token based bootstrap flow.  This includes signing a well known ConfigMap in the `kube-public` namespace and cleaning out expired tokens. ([#36101](https://github.com/kubernetes/kubernetes/pull/36101), [@jbeda](https://github.com/jbeda))

### ConfigMap

- **Federation**
  - [alpha] Support for ConfigMaps in federation. ([docs](http://kubernetes.io/docs/user-guide/federation/configmap/)) ([kubernetes/features#105](https://github.com/kubernetes/enhancements/issues/105))

* Implement dynamic provisioning (beta) of PersistentVolumes via StorageClass ([#29006](https://github.com/kubernetes/kubernetes/pull/29006), [@jsafrane](https://github.com/jsafrane))
* Allow setting permission mode bits on secrets, configmaps and downwardAPI files ([#28936](https://github.com/kubernetes/kubernetes/pull/28936), [@rata](https://github.com/rata))

### Immutable Secrets and ConfigMaps (beta)

Secret and ConfigMap volumes can be marked as immutable, which significantly reduces load on the API server if there are many Secret and ConfigMap volumes in the cluster.
See [ConfigMap](https://kubernetes.io/docs/concepts/configuration/configmap/) and [Secret](https://kubernetes.io/docs/concepts/configuration/secret/) for more information.

* Release the kubelet client certificate rotation as beta. ([#51045](https://github.com/kubernetes/kubernetes/pull/51045), [@jcbsmpsn](https://github.com/jcbsmpsn))
* Adds --append-hash flag to kubectl create configmap/secret, which will append a short hash of the configmap/secret contents to the name during creation. ([#49961](https://github.com/kubernetes/kubernetes/pull/49961), [@mtaufen](https://github.com/mtaufen))

feature gate to Beta and enabled the feature by default. This implies that 1) for new clusters kubeadm will start using the `kube-system/kubelet-config` naming scheme for the kubelet ConfigMap and RBAC rules, instead of the legacy `kubelet-config-x.yy` naming. 2) during upgrade, kubeadm will only write the new scheme ConfigMap and RBAC objects. To disable the feature you can pass `UnversionedKubeletConfigMap: false` in the kubeadm config for new clusters. For upgrade on existing clusters you can also override...

* kubelet: resolved hang/timeout issues when running large numbers of pods with unique configmap/secret references by reverting to 1.11 configmap/secret lookup behavior ([#74755](https://github.com/kubernetes/kubernetes/pull/74755), [@liggitt](https://github.com/liggitt))

- Apiservers based on k8s.io/apiserver with delegated authn based on cluster authentication will automatically update to new authentication information when the authoritative configmap is updated. ([#85004](https://github.com/kubernetes/kubernetes/pull/85004), [@deads2k](https://github.com/deads2k))