- Log messages in JSON format are written to stderr by default now (same as text format) instead of stdout. Users who expected JSON output on stdout must now capture stderr instead or in addition to stdout. ([#106146](https://github.com/kubernetes/kubernetes/pull/106146), [@pohly](https://github.com/pohly)) [SIG API Machinery, Architecture, Cluster Lifecycle and Instrumentation]

### Deprecation

- Controller-manager: the following flags have no effect and would be removed in v1.24:
  - `--port`
  - `--address`
  The insecure port flags `--port` may only be set to 0 now.
  
  In addtion, please be careful that:
  - controller-manager MUST start with `--authorization-kubeconfig` and `--authentication-kubeconfig` correctly set to get authentication/authorization working.

SIG Windows is also including several addition to this release:
 - Direct Server Return (DSR) mode support, allowing large numbers of services to scale up efficiently
 - Windows containers  now honor CPU limits

Note that snapshot support will require Kubernetes distributors to bundle the Snapshot controller, Snapshot CRDs, and validation webhook. In addition, a CSI driver supporting the snapshot functionality must also be deployed on the cluster.

### Non-recursive Volume Ownership (FSGroup) graduates to Beta

* In order to bypass graceful deletion of pods (to immediately remove the pod from the API) the user must now provide the `--force` flag in addition to `--grace-period=0`.  This prevents users from accidentally force deleting pods without being aware of the consequences of force deletion.  Force deleting pods for resources like StatefulSets can result in multiple pods with the same name having...

* Addition of Overhead field to the PodSpec and RuntimeClass types as part of the Pod Overhead KEP ([#76968](https://github.com/kubernetes/kubernetes/pull/76968), [@egernst](https://github.com/egernst))

## Changelog since v1.6.8

### Other notable changes

* StatefulSet: Set hostname/subdomain fields on new Pods in addition to the deprecated annotations, to allow mitigation of Pod DNS issues upon upgrading to Kubernetes v1.7.x. ([#50942](https://github.com/kubernetes/kubernetes/pull/50942), [@enisoc](https://github.com/enisoc))

  - [beta] `kube-apiserver` now publishes a swagger 2.0 spec in addition to a swagger 1.2 spec ([kubernetes/features#53](https://github.com/kubernetes/enhancements/issues/53))

Node selectors (to constrain pods to schedule on a subset of nodes) now support
the operators {<code>In, NotIn, Exists, DoesNotExist, Gt, Lt</code>}  instead of just conjunction of exact match on node label values. In
addition, we’ve introduced a new “soft” kind of node selector that is just a
hint to the scheduler; the scheduler will try to satisfy these requests but it
does not guarantee they will be satisfied. Both the “hard” and “soft” variants

  the cloud provider take both IPs into account. ([#120275](https://github.com/kubernetes/kubernetes/pull/120275), [@danwinship](https://github.com/danwinship))
- The `Dockerfile` for the kubectl image has been updated with the addition of a specific base image and essential utilities (bash and jq). ([#119592](https://github.com/kubernetes/kubernetes/pull/119592), [@rayandas](https://github.com/rayandas))