`--horizontal-pod-autoscaler-use-rest-clients` flag to `true`.

   - In version 1.9, this behavior will be enabled by default, and must be explicitly
     disabled by setting the `--horizontal-pod-autoscaler-use-rest-clients` flag to `false`.

### Cluster Lifecycle

- The `auto-detect` behavior of the kubelet's `--cloud-provider` flag is deprecated.

- Kubeadm: add the deprecated flag --port=0 to kube-controller-manager and kube-scheduler manifests to disable insecure serving. Without this flag the components by default serve (e.g. /metrics) insecurely on the default node interface (controlled by --address). Users that wish to override this behavior and enable insecure serving can pass...

## Action Required

- etcd2 as a backend is deprecated and support will be removed in Kubernetes 1.13.

StreamingProxyRedirects feature and `--redirect-container-streaming` flag are deprecated, and will be removed in a future release. The default behavior (proxy streaming requests through the kubelet) will be the only supported option. If you are setting `--redirect-container-streaming=true`, then you must migrate off this configuration. The flag will no longer be able to be enabled starting in v1.20. If you are not setting the flag, no action is necessary. ([#88290](https://github.com/kubernetes/ku...

- Added '--concurrent-cron-job-syncs' flag for `kube-controller-manager` to set the number of workers for cron job controller. ([#117550](https://github.com/kubernetes/kubernetes/pull/117550), [@borgerli](https://github.com/borgerli))

* kubectl port-forward no longer supports the deprecated -p <pod-name> flag; the flag itself is unnecessary and should be replaced by just the `<pod-name>`. ([#59705](https://github.com/kubernetes/kubernetes/pull/59705), [@phsiao](https://github.com/phsiao))

### **Node**

*   The kubelet `--network-plugin-dir` flag is removed. This flag was deprecated in version 1.7, and is replaced with `--cni-bin-dir`. ([#53564](https://github.com/kubernetes/kubernetes/pull/53564),[ @supereagle](https://github.com/supereagle))

 - Remove alpha `CSIMigrationXXComplete` flag and add alpha `InTreePluginXXUnregister` flag. Deprecate `CSIMigrationvSphereComplete` flag and it will be removed in v1.22. ([#98243](https://github.com/kubernetes/kubernetes/pull/98243), [@Jiawei0227](https://github.com/Jiawei0227))

- Kubelet: remove deprecated flag `--container-runtime` ([#114017](https://github.com/kubernetes/kubernetes/pull/114017), [@calvin0327](https://github.com/calvin0327)) [SIG Cloud Provider and Node]
- Kubelet: the deprecated `--master-service-namespace` flag is removed in v1.27 ([#116015](https://github.com/kubernetes/kubernetes/pull/116015), [@SataQiu](https://github.com/SataQiu))

* The deprecated `--service-account-private-key-file` flag has been removed from the cloud-controller-manager. The flag is still present and supported in the kube-controller-manager. ([#65182](https://github.com/kubernetes/kubernetes/pull/65182), [@liggitt](https://github.com/liggitt))