- API requests to deprecated versions now receive a warning header in the API response, and cause a metric indicating use of a deprecated API to be published:
  - `kubectl` outputs warnings to stderr, and accepts a `--warnings-as-errors` option to treat warnings as fatal errors

- [v1.6.0](#v160)
  - [Downloads for v1.6.0](#downloads-for-v160)
    - [Client Binaries](#client-binaries-13)
    - [Server Binaries](#server-binaries-13)
  - [WARNING: etcd backup strongly recommended](#warning-etcd-backup-strongly-recommended)
  - [Major updates and release themes](#major-updates-and-release-themes)
  - [Action Required](#action-required-1)
    - [Certificates API](#certificates-api)

* Delete all firewall rules (and optionally network) on GCE/GKE cluster teardown ([#34577](https://github.com/kubernetes/kubernetes/pull/34577), [@ixdy](https://github.com/ixdy))
* Fixed mutation warning in Attach/Detach controller ([#35273](https://github.com/kubernetes/kubernetes/pull/35273), [@jsafrane](https://github.com/jsafrane))

* AWS kube-up: Increase timeout waiting for docker start ([#25405](https://github.com/kubernetes/kubernetes/pull/25405), [@justinsb](https://github.com/justinsb))
* Fix hyperkube flag parsing ([#25512](https://github.com/kubernetes/kubernetes/pull/25512), [@colhom](https://github.com/colhom))

 *
 * <p>Throughout the documentation of this class, the phrase "matching character" is used to mean
 * "any {@code char} value {@code c} for which {@code this.matches(c)} returns {@code true}".
 *
 * <p><b>Warning:</b> This class deals only with {@code char} values, that is, <a
 * href="http://www.unicode.org/glossary/#BMP_character">BMP characters</a>. It does not understand

* kubectl: Fix bug that showed terminated/evicted pods even without `--show-all`. ([#48786](https://github.com/kubernetes/kubernetes/pull/48786), [@janetkuo](https://github.com/janetkuo))
* Add a runtime warning about the kubeadm default token TTL changes. ([#48838](https://github.com/kubernetes/kubernetes/pull/48838), [@mattmoyer](https://github.com/mattmoyer))

return data;\n    }\n  } else {\n    // if the arrowElement isn't a query selector we must check that the\n    // provided DOM node is child of its popper node\n    if (!data.instance.popper.contains(arrowElement)) {\n      console.warn(\n        'WARNING: `arrow.element` must be child of its popper element!'\n      );\n      return data;\n    }\n  }\n\n  const placement = data.placement.split('-')[0];\n  const { popper, reference } = data.offsets;\n  const isVertical = ['left', 'right'].indexOf(placement)...

lot more going on, processing the request and response, handling dependencies, executing **your own code**, and particularly, **waiting for the network**. But you will probably still get some nice performance improvements just from the upgrade.

The focus of this release is **compatibility** with Pydantic v1 and v2, to make sure your current apps keep working. Later there will be more focus on refactors, correctness, code improvements, and then **performance** improvements. Some third-party...

  Don't use these flags. Using deprecated flags causes the server to print a warning. Using a removed flag causes the server to abort the startup.

* The following deprecated flags were removed from `kubelet`:

  * `api-servers` - add apiserver addresses to the kubeconfig file instead.

  Don't use these flags. Using deprecated flags causes the kubelet to print a warning. Using a removed flag causes the kubelet to abort the startup.

## Changes by Kind

### Deprecation

- Added a [warning](https://k8s.io/blog/2020/09/03/warnings/) response when handling requests that set the deprecated `spec.externalID` field for a Node. ([#115944](https://github.com/kubernetes/kubernetes/pull/115944), [@SataQiu](https://github.com/SataQiu)) [SIG Node]
- Added warnings to the Services API. Kubernetes now warns for Services in the case of: