### Network

        * Switch to basing our image of Elasticsearch in fluentd-elasticsearch addon off the official one
        * Switch to the official image of Kibana in fluentd-elasticsearch addon
        * Use StatefulSet for Elasticsearch instead of ReplicationController, with persistent volume claims

- Kubectl: The deprecated `kubectl alpha debug` command is removed. Use `kubectl debug` instead. ([#98111](https://github.com/kubernetes/kubernetes/pull/98111), [@pandaamanda](https://github.com/pandaamanda)) [SIG CLI]

* kubectl built for darwin from darwin now enables cgo to use the system-native C libraries for DNS resolution. Cross-compiled kubectl (e.g. from an official kubernetes release) still uses the go-native netgo DNS implementation.  ([#64219](https://github.com/kubernetes/kubernetes/pull/64219), [@ixdy](https://github.com/ixdy))

- `kubeadm init` and `kubeadm init phase` now have a `--image-repository` flag, improving support for environments with limited access to official kubernetes repository.
- The DynamicKubeletConfig and SelfHosting functionality was moved outside of `kubeadm init` and feature gates and is now exposed under `kubeadm alpha`.

* duplicate kube-apiserver to federated-apiserver ([#23509](https://github.com/kubernetes/kubernetes/pull/23509), [@jianhuiz](https://github.com/jianhuiz))
* Kubelet: Start using the official docker engine-api ([#23506](https://github.com/kubernetes/kubernetes/pull/23506), [@Random-Liu](https://github.com/Random-Liu))

- Contextual logging is now in beta and enabled by default. Check out the [KEP](https://github.com/kubernetes/enhancements/issues/3077) and [official documentation](https://kubernetes.io/docs/concepts/cluster-administration/system-logs/#contextual-logging) for more details. ([#122589](https://github.com/kubernetes/kubernetes/pull/122589), [@pohly](https://github.com/pohly))

migration of data between different storage engines.  You must stop the API
from writing to etcd during an etcd2 -> etcd3 migration.  HA installations cannot
be migrated at the current time using the official Kubernetes procedure.

1.6 will also default to protobuf encoding if using etcd3.  **This change is
irreversible.**  To rollback, you must restore from a backup made before the

You can read more in the official blog post [Kubernetes Release Cadence Change: Here’s What You Need To Know](https://blog.k8s.io/2021/07/20/new-kubernetes-release-cadence/).

- Generating informers for packages in directories containing dots in their name is broken. This will be fixed in v1.16.1. ([#82860](https://github.com/kubernetes/kubernetes/issues/82860))