* `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))

    * `kubectl create secret` has a new option `--from-env-file` that populates a secret from file which follows a key=val format for each line.

  * Printing/describe

ASCII text.  There are four ways to represent the integer value
as a numeric constant: <code>\x</code> followed by exactly two hexadecimal
digits; <code>\u</code> followed by exactly four hexadecimal digits;
<code>\U</code> followed by exactly eight hexadecimal digits, and a
plain backslash <code>\</code> followed by exactly three octal digits.
In each case the value of the literal is the value represented by

- The plugin mechanism functionality now closely follows the git plugin design ([#66876](https://github.com/kubernetes/kubernetes/pull/66876), [@juanvallejo](https://github.com/juanvallejo))

- The kube-apiserver's Prometheus metrics have been extended with some that describe the costs of handling LIST requests.  They are as follows.
  - *apiserver_cache_list_total*: Counter of LIST requests served from watch cache, broken down by resource_prefix and index_name

   ([#120111](https://github.com/kubernetes/kubernetes/pull/120111), [@newtondev](https://github.com/newtondev))

### Promoted Server Side Unknown Field Validation to Beta

Promoted the `ServerSideFieldValidation` feature gate to beta (on by default). This allows optionally triggering schema validation on the API server that errors when unknown fields are detected. This allows the removal of client-side validation from kubectl while maintaining the same core functionality of erroring out on requests that contain unknown or invalid fields.

multiple smaller chunks. A client can specify a limit to the number of results to return. If more results exist, a token is returned that allows the client to continue the previous list call repeatedly until all results are retrieved.  The resulting list is identical to a list call that does not perform chunking, thanks to capabilities provided by etcd3.  This allows the server to use less memory and CPU when very large lists are returned. This feature is gated as APIListChunking and is not enabled by...

For stable features, the `kubectl` tool follows the Kubernetes [version skew policy](https://kubernetes.io/releases/version-skew-policy/);
however, kubectl v1.21 and older do not support the new API for ephemeral containers.

- kubeadm no longer allows using v1alpha3 configs for anything else than converting them to `v1beta1`. ([#74025](https://github.com/kubernetes/kubernetes/pull/74025), [@rosti](https://github.com/rosti))

node, turn on the feature gate `ReduceDefaultCrashLoopBackOffDecay`. If you are also using the feature gate `KubeletCrashLoopBackOffMax` with a configured per-node `CrashLoopBackOff.MaxContainerRestartPeriod`, the effective kubelet configuration will follow the conflict resolution policy described further in the documentation [here](https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle/#reduced-container-restart-delay). ([#130711](https://github.com/kubernetes/kubernetes/pull/130711), [@l...