* Mechanism of adding `federation domain maps` to kube-dns deployment via `--federations` flag is superseded by adding/updating `federations` key in `kube-system/kube-dns` configmap. If user is using kubefed tool to join cluster federation, adding federation domain maps to kube-dns is already taken care by `kubefed join` and does not need further action.

  PodSubnet validates against the corresponding cluster "--node-cidr-mask-size" of the kube-controller-manager, it fail if the values are not compatible.
  kubeadm no longer sets the node-mask automatically on IPv6 deployments, you must check that your IPv6 service subnet mask is compatible with the default node mask /64 or set it accordingly.

* Make DaemonSet respect critical pods annotation when scheduling. ([#42028](https://github.com/kubernetes/kubernetes/pull/42028), [@janetkuo](https://github.com/janetkuo))
* Implement the update feature for DaemonSet. ([#41116](https://github.com/kubernetes/kubernetes/pull/41116), [@lukaszo](https://github.com/lukaszo))

* Add flag "--include-uninitialized" to kubectl annotate, apply, edit-last-applied, delete, describe, edit, get, label, set. "--include-uninitialized=true" makes kubectl commands apply to uninitialized objects, which by default are ignored if the names of the objects are not provided. "--all" also makes kubectl commands apply to uninitialized objects. Please see the [initializer](https://kubernetes.io/docs/admin/extensible-admission-controllers/) doc for more details. ([#5049...

consequence, all volume mounts in containers are now `rslave` on Linux by default. To make this default work in all Linux environments the entire mount tree should be marked as shareable, e.g. via `mount --make-rshared /`. All Linux distributions that use systemd already have the root directory mounted as rshared and hence they need not do anything. In Linux environments without systemd we recommend running `mount --make-rshared /` during boot before docker is started, ([@jsafrane](https://github.com/jsafrane))...

 Extended resources cannot be overcommitted, so make sure that request and limit are equal
 if both are present in a container spec.

 - The default Bootstrap Token created with `kubeadm init` v1.8 expires
 and is deleted after 24 hours by default to limit the exposure of the
 valuable credential. You can create a new Bootstrap Token with
 `kubeadm token create` or make the default token permanently valid by specifying

- **Admission webhooks:** Admission webhooks are in widespread use as a Kubernetes extensibility mechanism and have been available in beta since the 1.9 release. The 1.16 release marks the graduation of admission webhooks to general availability (GA).

    * Bump metadata agent version to 0.2-0.0.21-1.
    * Expand the metadata agent's access to all API groups.
    * Remove metadata agent config maps in favor of command line flags.
    * Update the metadata agent's liveness probe to a new /healthz handler.
    * Logging Agent Improvements
    * Bump logging agent version to 0.2-1.5.33-1-k8s-1.

* fix: make azure disk URI as case insensitive ([#79020](https://github.com/kubernetes/kubernetes/pull/79020), [@andyzhangx](https://github.com/andyzhangx))

- Kubeadm: during execution of the "check expiration" command, treat the etcd CA as external if there is a missing etcd CA key file (etcd/ca.key) and perform the proper validation on certificates signed by the etcd CA. Additionally, make sure that the CA for all entries in the output table is included - for both certificates on disk and in kubeconfig files. ([#106924](https://github.com/kubernetes/kubernetes/pull/106924), [@neolit123](https://github.com/neolit123)) [SIG Cluster Lifecycle]...