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* kubeadm: Enable kubelet client certificate rotation ([#52196](https://github.com/kubernetes/kubernetes/pull/52196), [@luxas](https://github.com/luxas))
* Scheduler predicate developer should respect equivalence class cache ([#52146](https://github.com/kubernetes/kubernetes/pull/52146), [@resouer](https://github.com/resouer))

containers](https://kubernetes.io/docs/concepts/workloads/pods/ephemeral-containers/), it became more obvious how we can support developers with tooling built on top of `kubectl exec`. The addition of the `kubectl debug` [command](https://github.com/kubernetes/enhancements/blob/master/keps/sig-cli/1441-kubectl-debug/README.md) (it is alpha but your feedback is more than welcome), allows developers to easily debug their Pods inside the cluster. We think this addition is invaluable.  This command allows one to create...

## Changelog since v1.27.0

## Urgent Upgrade Notes 

### (No, really, you MUST read this before you upgrade)

- Action required for the custom scheduler plugin developers. 
  Here's the breaking change in `EnqueueExtension` in the scheduling framework. 

* MESOS: forward globally declared cadvisor housekeeping flags ([#22974](https://github.com/kubernetes/kubernetes/pull/22974), [@jdef](https://github.com/jdef))
* Trusty: support developer workflow on base image ([#22960](https://github.com/kubernetes/kubernetes/pull/22960), [@andyzheng0831](https://github.com/andyzheng0831))



# v1.2.0

* MESOS: forward globally declared cadvisor housekeeping flags ([#22974](https://github.com/kubernetes/kubernetes/pull/22974), [@jdef](https://github.com/jdef))
* Trusty: support developer workflow on base image ([#22960](https://github.com/kubernetes/kubernetes/pull/22960), [@andyzheng0831](https://github.com/andyzheng0831))

  * Plugins

      * Introduces the ability to extend kubectl by adding third-party plugins. Developer preview, please refer to the documentation for instructions about how to use it. ([#37499](https://github.com/kubernetes/kubernetes/pull/37499), [@fabianofranz](https://github.com/fabianofranz))

Pruning is activated by setting `spec.preserveUnknownFields: false` in the CustomResourceDefinition. A future apiextensions.k8s.io/v1 variant of CRDs will enforce pruning.

- Service session affinity timeout tests are no longer required for Kubernetes network plugin conformance due to variations in existing implementations. New conformance tests will be developed to better express conformance in future releases. ([#112806](https://github.com/kubernetes/kubernetes/pull/112806), [@dcbw](https://github.com/dcbw)) [SIG Architecture, Network and Testing]

    * The body size limit does not apply to subresources like pods/proxy that proxy request content to another server.
* Kustomize is developed in its own repo https://github.com/kubernetes-sigs/kustomize ([#73033](https://github.com/kubernetes/kubernetes/pull/73033), [@Liujingfang1](https://github.com/Liujingfang1))
    * This PR added a new subcommand `kustomize` in kubectl.