* kubectl: This client version requires the `apps/v1` APIs, so it will not work against a cluster version older than v1.9.0. Note that kubectl only guarantees compatibility with clusters that are +/-1 minor version away. ([#61419](https://github.com/kubernetes/kubernetes/pull/61419), [@enisoc](https://github.com/enisoc))

[@yujuhong](https://github.com/yujuhong))

* The Container Runtime Interface (CRI) version has increased from v1alpha1 to v1alpha2. Runtimes implementing the CRI will need to update to the new version, which configures container namespaces using an enumeration rather than booleans. This change to the alpha API is not backwards compatible; implementations of the CRI such as containerd, will need to update to the new API version. ([#58973](https://github.com/kubernetes/kubernetes/pull/58973), [@verb](htt...

### Autoscaling

 - Consuming metrics directly from Heapster is deprecated in favor of
   consuming metrics via an aggregated version of the resource metrics API.

   - In version 1.8, enable this behavior by setting the
     `--horizontal-pod-autoscaler-use-rest-clients` flag to `true`.

## External Dependency Version Information

Continuous integration builds have used the following versions of external dependencies, however, this is not a strong recommendation and users should consult an appropriate installation or upgrade guide before deciding what versions of etcd, docker or rkt to use.

* Docker versions 1.10.3, 1.11.2, 1.12.6 have been validated
  * Docker version 1.12.6 known issues

### Apps

The core workloads API, which is composed of the DaemonSet, Deployment, ReplicaSet, and StatefulSet kinds, has been promoted to GA stability in the apps/v1 group version. As such, the apps/v1beta2 group version is deprecated, and all new code should use the kinds in the apps/v1 group version.

### Auth

## **External Dependency Version Information**

Continuous integration builds have used the following versions of external dependencies, however, this is not a strong recommendation and users should consult an appropriate installation or upgrade guide before deciding what versions of etcd, docker or rkt to use.

* Docker versions 1.10.3, 1.11.2, 1.12.6 have been validated

- Kubeadm: updated the supported etcd version to v3.5.23 for supported control plane versions v1.31, v1.32, and v1.33. ([#134692](https://github.com/kubernetes/kubernetes/pull/134692), [@joshjms](https://github.com/joshjms)) [SIG Cluster Lifecycle and Etcd]

- The resource version option, when passed to a list call, is now consistently interpreted as the minimum allowed resource version.  Previously when listing resources that had the watch cache disabled clients could retrieve a snapshot at that exact resource version.  If the client requests a resource version newer than the current state, a TimeoutError is returned suggesting the client retry in a few seconds....

- The list of validated docker versions remain unchanged at 1.11.1, 1.12.1, 1.13.1, 17.03, 17.06, 17.09, 18.06 since Kubernetes 1.12. ([#68495](https://github.com/kubernetes/kubernetes/pull/68495))
- The default Go version was updated to 1.11.2. ([#70665](https://github.com/kubernetes/kubernetes/pull/70665))
- The minimum supported Go version was updated to 1.11.2 ([#69386](https://github.com/kubernetes/kubernetes/pull/69386))

- Kubeadm: upgrade supports fallback to the nearest known etcd version if an unknown k8s version is passed ([#88373](https://github.com/kubernetes/kubernetes/pull/88373), [@SataQiu](https://github.com/SataQiu)) [SIG Cluster Lifecycle]