## External Dependencies

* Default etcd server version is v3.2.18 compared with v3.1.12 in v1.10 ([#61198](https://github.com/kubernetes/kubernetes/pull/61198))
* Rescheduler is v0.4.0, compared with v0.3.1 in v1.10 ([#65454](https://github.com/kubernetes/kubernetes/pull/65454))
* The validated docker versions are the same as for v1.10: 1.11.2 to 1.13.1 and 17.03.x (ref)

- `kubeadm`: will now allow deploying a kubelet that is 3 versions older than the version of `kubeadm` (N-3). This aligns with the recent change made by SIG Architecture that extends the support skew between the control plane and kubelets. Tolerate this new kubelet skew for the commands `init`, `join` and `upgrade`. Note that if the `kubeadm` user applies a control plane version that is older than the `kubeadm` version (N-1 maximum) then the skew between the kubelet and control plane would...

  - `spec.version` is removed in v1; use `spec.versions` instead
  - `spec.validation` is removed in v1; use `spec.versions[*].schema` instead
  - `spec.subresources` is removed in v1; use `spec.versions[*].subresources` instead
  - `spec.additionalPrinterColumns` is removed in v1; use `spec.versions[*].additionalPrinterColumns` instead

For stable features, the `kubectl` tool follows the Kubernetes [version skew policy](https://kubernetes.io/releases/version-skew-policy/);
however, kubectl v1.21 and older do not support the new API for ephemeral containers.

## 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

    - [Am I vulnerable?](#am-i-vulnerable)
      - [Affected Versions](#affected-versions)
    - [How do I mitigate this vulnerability?](#how-do-i-mitigate-this-vulnerability)
      - [Fixed Versions](#fixed-versions)
    - [Detection](#detection)
      - [Additional Details](#additional-details)
      - [Acknowledgements](#acknowledgements)

  when the kernel version was 4.15 or higher. With the kernel 4.15 the sysctl became namespaced.
  Pod Security admission allowed these sysctl in v1.32+ versions of the baseline and restricted policies. ([#127489](https://github.com/kubernetes/kubernetes/pull/127489), [@pacoxu](https://github.com/pacoxu)) [SIG Auth, Network and Node]

- The go version defined in `.go-version` is now fetched when invoking test, build, and code generation targets if the current go version does not match it. Set $FORCE_HOST_GO=y while testing or building to skip this behavior, or set $GO_VERSION to override the selected go version. ([#115377](https://github.com/kubernetes/kubernetes/pull/115377), [@liggitt](https://github.com/liggitt)) [SIG Testing]...

### 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`.

- The go version defined in `.go-version` is now fetched when invoking test, build, and code generation targets if the current go version does not match it. Set $FORCE_HOST_GO=y while testing or building to skip this behavior, or set $GO_VERSION to override the selected go version. ([#115497](https://github.com/kubernetes/kubernetes/pull/115497), [@liggitt](https://github.com/liggitt)) [SIG Release...