- kubeadm no longer dumps backtrace if it fails to remove the running containers on reset. ([#73951](https://github.com/kubernetes/kubernetes/pull/73951), [...

    *   Federation-specific behavior will no longer be included in kubectl
    *   kubefed will no longer be released as part of Kubernetes
    *   The Federation servers will no longer be included in the hyperkube binary and image. ([#53816](https://github.com/kubernetes/kubernetes/pull/53816),[ @marun](https://github.com/marun))

### **Node**

### API Machinery

* The Namespace API object no longer supports the deletecollection operation. ([#46407](https://github.com/kubernetes/kubernetes/pull/46407), [@liggitt](https://github.com/liggitt))

- Correct a reference to a not/no longer used kustomize subcommand in the documentation ([#82535](https://github.com/kubernetes/kubernetes/pull/82535), [@demobox](https://github.com/demobox))

* The deprecated alpha and beta initContainer annotations are no longer supported. Init containers must be specified using the initContainers field in the pod spec. ([#51816](https://github.com/kube...

you MUST read this before you upgrade)

- Kube-proxy's IPVS proxy mode no longer sets the net.ipv4.conf.all.route_localnet sysctl parameter. Nodes upgrading will have net.ipv4.conf.all.route_localnet set to 1 but new nodes will inherit the system default (usually 0). If you relied on any behavior requiring net.ipv4.conf.all.route_localnet, you must set ensure it is enabled as kube-proxy will no longer set it automatically. This change helps to further mitigate CVE-2020-8558. ([#92938]...

  - A `create` or `update` API request with duplicate items in a keyed list no longer wipes out managedFields. Examples include env var entries with the same name, or port entries with the same containerPort in a pod spec.
  - A server-side apply request that makes unrelated changes to an object which has duplicate items in a keyed list no longer fails, and leaves the existing duplicate items as-is.

- `Kubectl set resources` will no longer return an error if passed an empty change for a resource. `kubectl set subject` will no longer return an error if passed an empty change for a resource. ([#85490](https://github.com/kubernetes/kubernetes/pull/85490), [@sallyom](https://github.com/sallyom)) [SIG CLI]

- API
  - Ingress resources will no longer be served from `extensions/v1beta1` in v1.19. Migrate use to the `networking.k8s.io/v1beta1` API, available since v1.14. Existing persisted data can be retrieved via the `networking.k8s.io/v1beta1` API.

[@rosti](https://github.com/rosti)) Courtesy of SIG Cluster Lifecycle, SIG Release, and SIG Testing