- When specifying an invalid value for a label, it was not always clear which label the value was specified for. Starting with this release, the label's key is included in such error messages, which makes debugging easier. ([#77144](https://github.com/kubernetes/kubernetes/pull/77144), [@kenegozi](https://github.com/kenegozi))

  pre-1.0 to 1.6 kubelet is not supported.
* Fluentd was migrated to Daemon Set, which targets nodes with
  beta.kubernetes.io/fluentd-ds-ready=true label. If you use fluentd in your
  cluster please make sure that the nodes with version 1.6+ contains this
  label.

### kubectl
* Running `kubectl taint` (alpha in 1.5) against a 1.6 server requires upgrading kubectl to version 1.6

- Added a new metric `apiserver_encryption_config_controller_automatic_reloads_total` to measure the total number of API server encryption configuration reload successes and failures.  This metric now contains the `status` label with a value that is either `success` or `failure`. Deprecated the metrics `apiserver_encryption_config_controller_automatic_reload_success_total` and `apiserver_encryption_config_controller_automatic_reload_failure_total`. Please use `apiserver_e...

- If upgrading Cluster Federation components from 1.3.x, please ensure your cluster name is a valid DNS label (#30956, @nikhiljindal)
- kubelet's `--config` flag has been deprecated, use `--pod-manifest-path` instead (#29999, @mtaufen)

     * Spec change:
        * Deployment’s [selector](http://kubernetes.io/docs/user-guide/labels/#label-selectors) is now more general (supports set-based selector; it only supported
equality-based selector in 1.1).
        * .spec.uniqueLabelKey is removed -- users can’t customize unique label key --
and its default value is changed from
“deployment.kubernetes.io/podTemplateHash” to “pod-template-hash”.

    * setting `KUBE_PROXY_DAEMONSET=true` in kube-up will now set a `node.kubernetes.io/kube-proxy-ds-ready=true` label on new nodes. In v1.16, the kube-proxy daemonset add-on will switch to using that label as a node selector.

- '`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.'
   ([#113699](https://github.com/kubernetes/kubernetes/pull/113699), [@liggitt](https://github.com/liggitt))

* kubeadm: Don't set a specific `spc_t` SELinux label on the etcd Static Pod as that is more privs than etcd needs and due to that `spc_t` isn't compatible with some OSes. ([#49328](https://github.com/kubernetes/kubernetes/pull/49328), [@euank](https://github.com/euank))

legacy auto-generated service account token secrets are auto-labeled with a `kubernetes.io/legacy-token-invalid-since` label if the credentials have not been used in the time specified by `--legacy-service-account-token-clean-up-period` (defaulting to one year), **and** are referenced from the `.secrets` list of a ServiceAccount object, **and**  are not referenced from pods. This label causes the authentication layer to reject use of the credentials. After being labeled as invalid, if the time specified...

* Fixed check in kubectl autoscale: cpu consumption can be higher than 100%. ([#26162](https://github.com/kubernetes/kubernetes/pull/26162), [@jszczepkowski](https://github.com/jszczepkowski))
* Add support for 3rd party objects to kubectl label ([#24882](https://github.com/kubernetes/kubernetes/pull/24882), [@brendandburns](https://github.com/brendandburns))