* The kubeadm configuration file version has been upgraded from `v1alpha1` to `v1alpha2`. `v1alpha1` read support exists in v1.11, but will be removed in v1.12. ([#63788](https://github.com/kubernetes/kubernetes/pull/63788), [@luxas](https://github.com/luxas))
The following PRs changed the API spec:

- The `NodeConfiguration` kind in the kubeadm v1alpha2 API has been renamed `JoinConfiguration` in v1alpha3 ([#65951](https://github.com/kubernetes/kubernetes/pull/65951), [@luxas](https://github.com/luxas)) Courtesy of SIG Cluster Lifecycle

    * rbac.authorization.k8s.io/v1alpha1
    * settings.k8s.io/v1alpha1
    * If you wish to continue using them in v1.8, please enable them explicitly using the `--runtime-config` flag of the apiserver (for example, `--runtime-config="rbac.authorization.k8s.io/v1alpha1,settings.k8s.io/v1alpha1"`)

be sure to upgrade Docker before upgrading Kubernetes. ([#57845](https://github.com/kubernetes/kubernetes/pull/57845), [@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...

  to kubelet config ([#112136](https://github.com/kubernetes/kubernetes/pull/112136), [@pacoxu](https://github.com/pacoxu))
- `resource.k8s.io/v1alpha1` was replaced with `resource.k8s.io/v1alpha2`. Before
  upgrading a cluster, all objects in resource.k8s.io/v1alpha1 (ResourceClaim, ResourceClaimTemplate,
  ResourceClass, PodScheduling) must be deleted. The changes are internal, so

    * rbac.authorization.k8s.io/v1alpha1

    * settings.k8s.io/v1alpha1

    * If you wish to continue using them in v1.8, please enable them explicitly using the `--runtime-config` flag on the apiserver (for example, `--runtime-config="rbac.authorization.k8s.io/v1alpha1,settings.k8s.io/v1alpha1"`)

*   The API group/version for the kube-proxy configuration has changed from `componentconfig/v1alpha1` to `kubeproxy.config.k8s.io/v1alpha1`. If you are using a config file for kube-proxy instead of the command line flags, you must change its apiVersion to `kubeproxy.config.k8s.io/v1alpha1`. ([#53645](https://github.com/kubernetes/kubernetes/pull/53645), [@xiangpengzhao](https://github.com/xiangpengzhao))

If a container runtime does not support the `v1` API, Kubernetes will fall back to the `v1alpha2` implementation.
There is no intermediate action required by end-users, because `v1` and `v1alpha2` do not differ in their implementation.
It is likely that `v1alpha2` will be removed in one of the future Kubernetes releases to be able to develop `v1`.

### Structured logging graduate to Beta

- The `client.authentication.k8s.io/v1alpha1` ExecCredential has been removed. If you are using a client-go credential plugin that relies on the v1alpha1 API please contact the distributor of your plugin for instructions on how to migrate to the v1 API. ([#108616](https://github.com/kubernetes/kubernetes/pull/108616), [@margocrawf](https://github.com/margocrawf))

* [action required] kubeadm: The `v1alpha2` config API has been removed. ([#69055](https://github.com/kubernetes/kubernetes/pull/69055), [@fabriziopandini](https://github.com/fabriziopandini))
    * Please convert your `v1alpha2` configuration files to `v1alpha3` using the
    * `kubeadm config migrate` command of kubeadm v1.12.x

### Other notable changes