* Add SIGCHLD handler to pause container ([#36853](https://github.com/kubernetes/kubernetes/pull/36853), [@verb](https://github.com/verb))
* Populate environment variables from a secrets. ([#39446](https://github.com/kubernetes/kubernetes/pull/39446), [@fraenkel](https://github.com/fraenkel))

- `kubectl alpha debug` now supports debugging nodes by creating a debugging container running in the node's host namespaces. ([#92310](https://github.com/kubernetes/kubernetes/pull/92310), [@verb](https://github.com/verb)) [SIG CLI]

* Build test targets for all server platforms ([#51873](https://github.com/kubernetes/kubernetes/pull/51873), [@luxas](https://github.com/luxas))

- Ephemeral containers graduated to beta and are now available by default. ([#105405](https://github.com/kubernetes/kubernetes/pull/105405), [@verb](https://github.com/verb))

* Fix panic for attaching AzureDisk to vmss nodes ([#63275](https://github.com/kubernetes/kubernetes/pull/63275), [@feiskyer](https://github.com/feiskyer))
* `kubectl api-resources` now supports filtering to resources supporting specific verbs, and can output fully qualified resource names suitable for combining with commands like `kubectl get` ([#63254](https://github.com/kubernetes/kubernetes/pull/63254), [@liggitt](https://github.com/liggitt))

* Adds a metric apiserver_request_error_total to kube-apiserver. This metric tallies the number of request_errors encountered by verb, group, version, resource, subresource, scope, component, and code. ([#84780](https://github.com/kubernetes/kubernetes/pull/84780), [@RainbowMango](https://github.com/RainbowMango))

### Feature

- Added KMS `v2alpha1` API. ([#110201](https://github.com/kubernetes/kubernetes/pull/110201), [@aramase](https://github.com/aramase))

  If the API server does not support or allow streaming, then `client-go` falls back to fetching the collection using the **list** API verb. ([#127388](https://github.com/kubernetes/kubernetes/pull/127388), [@p0lyn0mial](https://github.com/p0lyn0mial)) [SIG API Machinery and Testing]

- Registered metric `apiserver_request_body_size_bytes` to track the size distribution of requests by `resource` and `verb`. ([#120474](https://github.com/kubernetes/kubernetes/pull/120474), [@YaoC](https://github.com/YaoC)) [SIG API Machinery and Instrumentation]

- Pod spread constraints have been added in alpha. You can use these constraints to control how Pods are spread across the cluster among failure-domains. ([#77327](https://github.com/kubernetes/kubernetes/pull/77327), [#77760](...