* 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

* You must now specify `Node.Spec.ConfigSource.ConfigMap.KubeletConfigKey` when using dynamic Kubelet config to tell the Kubelet which key of the `ConfigMap` identifies its config file. ([#59847](https://github.com/kubernetes/kubernetes/pull/59847), [@mtaufen](https://github.com/mtaufen))

```

If your cluster was installed by kubeadm, you should edit the `featureGates` field in the `kubeadm-config` ConfigMap. You can do this using `kubectl -n kube-system edit cm kubeadm-config` before upgrading. For example:

kubeadm-config Before:

```
apiVersion: v1
kind: ConfigMap
metadata:
  name: kubeadm-config
data:
  MasterConfiguration: |
    kubeProxy:
      config:

    * `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))

- Resolves spurious `Failed to list *v1.Secret` or `Failed to list *v1.ConfigMap` messages in kubelet logs. ([#99538](https://github.com/kubernetes/kubernetes/pull/99538), [@liggitt](https://github.com/liggitt)) [SIG Auth and Node]

* 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))

### 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.

### Structured Logging in Kubelet

* 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))

- Kubeadm: fix a regression where the KubeletConfiguration is not properly downloaded during "kubeadm upgrade" commands from the kube-system/kubelet-config ConfigMap, resulting in the local '/var/lib/kubelet/config.yaml' file being written as a defaulted config. ([#124497](https://github.com/kubernetes/kubernetes/pull/124497), [@neolit123](https://github.com/neolit123)) [SIG Cluster Lifecycle]

  - [Known Issues](#known-issues)
    - [LocalStorageCapacityIsolationFSQuotaMonitoring ConfigMap rendering failure](#localstoragecapacityisolationfsquotamonitoring-configmap-rendering-failure)
  - [Urgent Upgrade Notes](#urgent-upgrade-notes)
    - [(No, really, you MUST read this before you upgrade)](#no-really-you-must-read-this-before-you-upgrade)