* You can now set `VolumeMount.Propagation` to `Bidirectional` to enable a particular mount for a container to propagate itself to the host or other containers.

* [alpha] Improve Flex volume deployment

  * Flex volume driver deployment is simplified in the following ways:

    * New driver files can now be automatically discovered and initialized without requiring a kubelet or controller-manager restart.

> - End Sha: 337e0e18f1aefa199bd0a1786f8eab42e948064c

## Known Issues

### Deprecation

#### kube-apiserver:
- the following deprecated APIs can no longer be served:
  - All resources under `apps/v1beta1` and `apps/v1beta2` - use `apps/v1` instead
  - `daemonsets`, `deployments`, `replicasets` resources under `extensions/v1beta1` - use `apps/v1` instead
  - `networkpolicies` resources under `extensions/v1beta1` - use `networking.k8s.io/v1` instead

- Kube-proxy handles Terminating EndpointSlices conditions and enables zero downtime deployments for Services with ExternalTrafficPolicy=Local author: @andrewsykim ([#117718](https://github.com/kubernetes/kubernetes/pull/117718), [@aojea](https://github.com/aojea)) [SIG Network, Testing and Windows]

create Deployment Beta resources after upgrading to 1.2. Not deleting the
Deployment objects may cause the deployment controller to mistakenly match
other pods and delete them, due to the selector API change.
     * Client (kubectl) and server versions must match (both 1.1 or both 1.2) for any
Deployment-related operations.
     * Behavior change:
        * Deployment creates ReplicaSets instead of ReplicationControllers.

- Kube-controller-manager: Fixes bug setting headless service labels on endpoints ([#85361](https://github.com/kubernetes/kubernetes/pull/85361),...

## Notable Changes to Existing Behavior

### Deployments

- ReplicaSets of paused Deployments are now scaled while the Deployment is paused. This is retroactive to existing Deployments.
- When scaling a Deployment during a rollout, the ReplicaSets of all Deployments are now scaled proportionally based on the number of replicas they each have instead of only scaling the newest ReplicaSet.

    *   Support for IPv6-only Kubernetes cluster deployments. **<span style="text-decoration:underline;">Note:</span>** This feature does not provide dual-stack support.
    *   Support for IPv6 Kubernetes control and data planes.
    *   Support for Kubernetes IPv6 cluster deployments using kubeadm.
    *   Support for the iptables kube-proxy backend using ip6tables.

* Use debian-base instead of busybox as base image for server images ([#70245](ht...

### Deployment
* Add ready replicas in Deployments ([#37959](https://github.com/kubernetes/kubernetes/pull/37959), [@kargakis](https://github.com/kargakis))
* Deployments that cannot make progress in rolling out the newest version will now indicate via the API they are blocked