### SIG Storage

Google Cloud required that workloads (e.g. Deployments, DaemonSets, etc.) which used `PersistentDisk` volumes were using them in read-only mode.  This validation provided very little value at relatively host implementation cost, and will no longer be validated.  If this is a problem for a specific use-case, please set the `SkipReadOnlyValidationGCE` gate to false to re-enable the validation, and file a Kubernetes bug with details. ([#121083](https://github.com/kubernetes/kubernetes/pull/121083), [@tho...

* **Other objects**: no changes unless you explicitly request orphaning.

## Action Required Before Upgrading

- If you are using Kubernetes to manage `docker` containers, please be aware Kubernetes has been validated to work with docker 1.9.1, docker 1.11.2 (#23397), and docker 1.12.0 (#28698)

* Docker versions 1.10.3, 1.11.2, 1.12.6 have been validated

    * Docker version 1.12.6 known issues

        * overlay2 driver not fully supported

        * live-restore not fully supported

        * no shared pid namespace support

- Validated APIVersion fields of the `HorizontalPodAutoscaler` to ensure that API objects were created and functioned properly. ([#132537](https://github.com/kubernetes/kubernetes/pull/132537), [@lalitc375](https://github.com/lalitc375)) [SIG Etcd and Testing]...

[CRD Validation Expression Language](https://github.com/kubernetes/enhancements/blob/master/keps/sig-api-machinery/2876-crd-validation-expression-language/README.mdv) is promoted to beta, which makes it possible to declare how custom resources are validated using the [Common Expression Language (CEL)](https://github.com/google/cel-spec). Please see the [validation rules](https://kubernetes.io/docs/tasks/extend-kubernetes/custom-resources/custom-resource-definitions/#validation-rules) guide.

- On compatible systems, a mounter's Unmount implementation is changed to not return an error when the specified target can be detected as not a mount point. On Linux, the behavior of detecting a mount point depends on `umount` command is validated when the mounter is created. Additionally, mount point checks will be skipped in CleanupMountPoint/CleanupMountWithForce if the mounter's Unmount having the changed behavior of not returning error when target is not a mount point. ([#109676](htt...

* 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)
* The Go version is go1.10.2, as compared to go1.9.3 in v1.10. ([#63412](https://github.com/kubernetes/kubernetes/pull/63412))

##  External Dependencies

- Default etcd server is unchanged at v3.2.24 since Kubernetes 1.12. ([#68318](https://github.com/kubernetes/kubernetes/pull/68318))
- 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))

  healthy.'
   ([#113375](https://github.com/kubernetes/kubernetes/pull/113375), [@atiratree](https://github.com/atiratree))
- '`metav1.LabelSelectors` specified in API objects are now validated to ensure
  they do not contain invalid label values that will error at time of use. Existing
  invalid objects can be updated, but new objects are required to contain valid
  label selectors.'