- Scheduler Policy API has a new recommended apiVersion `apiVersion: kubescheduler.config.k8s.io/v1` which is consistent with the scheduler API group `kubescheduler.config.k8s.io`. It holds the same API as the old apiVersion `apiVersion: v1`. ([#83578](https://github.com/kubernetes/kubernetes/pull/83578), [@Huang-Wei](https://github.com/Huang-Wei))

* Kubectl explain now prints out the Kind and API version of the resource being explained. ([#55689](https://github.com/kubernetes/kubernetes/pull/55689), [@luksa](https://github.com/luksa))

### Cluster Lifecycle

* The default Kubernetes version for kubeadm is now 1.10. ([#61127](https://github.com/kubernetes/kubernetes/pull/61127), [@timothysc](https://github.com/timothysc))

* 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))

- kube-scheduler dropped support for configuration files with apiVersion `componentconfig/v1alpha1`. Ensure kube-scheduler is configured using command-line flags or a configuration file with apiVersion `kubescheduler.config.k8s.io/v1alpha1` before upgrading to 1.13.
- kubectl

* Fixes an issue with missing apiVersion/kind in object data sent to admission webhooks ([#74448](https://github.com/kubernetes/kubernetes/pull/74448), [@liggitt](https://github.com/liggitt))

pkg syscall (darwin-arm64), type BpfStat struct, Drop uint32
pkg syscall (darwin-arm64), type BpfStat struct, Recv uint32
pkg syscall (darwin-arm64), type BpfVersion struct
pkg syscall (darwin-arm64), type BpfVersion struct, Major uint16
pkg syscall (darwin-arm64), type BpfVersion struct, Minor uint16
pkg syscall (darwin-arm64), type Cmsghdr struct
pkg syscall (darwin-arm64), type Cmsghdr struct, Len uint32

pkg syscall (netbsd-arm64-cgo), type BpfTimeval struct, Usec int64
pkg syscall (netbsd-arm64-cgo), type BpfVersion struct
pkg syscall (netbsd-arm64-cgo), type BpfVersion struct, Major uint16
pkg syscall (netbsd-arm64-cgo), type BpfVersion struct, Minor uint16
pkg syscall (netbsd-arm64-cgo), type Cmsghdr struct
pkg syscall (netbsd-arm64-cgo), type Cmsghdr struct, Len uint32

* rkt version 1.23.0+

    * known issues with the rkt runtime are [listed in the Getting Started Guide](https://kubernetes.io/docs/getting-started-guides/rkt/notes/)

* etcd version 3.0.17

* Go version: 1.8.3. [Link to announcement](https://groups.google.com/d/msg/kubernetes-dev/0XRRz6UhhTM/YODWVnuDBQAJ)

- 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]

### 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`.