- Autoscaling/v2beta2 and custom_metrics/v1beta2 have been introduced, which implement metric selectors for Object and Pods metrics, as well as allowing AverageValue targets on Objects, similar to External metrics. ([#64097](https://github.com/kubernetes/kubernetes/pull/64097), [@damemi](https://github.com/damemi)) Courtesy of SIG API Machinery, SIG Architecture, SIG Autoscaling, SIG CLI, and SIG Testing

- ACTION REQUIRED: Support for basic authentication via the --basic-auth-file flag has been removed.  Users should migrate to --token-auth-file for similar functionality. ([#89069](https://github.com/kubernetes/kubernetes/pull/89069), [@enj](https://github.com/enj)) [SIG API Machinery]

- `kubectl debug` gains support for changing container images when copying a pod for debugging, similar to how `kubectl set image` works. See `kubectl help debug` for more information. ([#96058](https://github.com/kubernetes/kubernetes/pull/96058), [@verb](https://github.com/verb)) [SIG CLI]

### Documentation

Kubeadm: Expose the `kubeadm join` workflow as phases

- Kubeadm: added support for dry running `kubeadm reset`. The new flag `kubeadm reset --dry-run` is similar to the existing flag for `kubeadm init/join/upgrade` and allows you to see what changes would be applied. ([#107512](https://github.com/kubernetes/kubernetes/pull/107512), [@SataQiu](https://github.com/SataQiu))

    * - kubeadm upgrade apply supports all standard ways of specifying version via labels. Examples: stable-1.8, latest-1.8, ci/latest-1.9 and similar.
* - kubeadm 1.9 will detect and fail init or join pre-flight checks if kubelet is lower than 1.8.0-alpha ([#52913](https://github.com/kubernetes/kubernetes/pull/52913), [@kad](https://github.com/kad))

### Storage

- Fixes a bug of identifying the correct containerd process. ([#97888](https://github.com/kubernetes/kubernetes/pull/97888), [@pacoxu](https://github.com/pacoxu))
- Fixes add-on manager leader election to use leases instead of endpoints, similar to what kube-controller-manager does in 1.20 ([#98968](https://github.com/kubernetes/kubernetes/pull/98968), [@liggitt](https://github.com/liggitt))

- Ephemeral containers have been added in alpha. These temporary containers can be added to running pods for purposes such as debugging, similar to how `kubectl exec` runs a process in an existing container. Also like `kubectl exec`, no resources are reserved for ephemeral containers and they are not restarted when they exit. Note that container namespace targeting is not yet implemented,...

er/keps/sig-storage/596-csi-inline-volumes) feature allows CSI volumes to be specified directly in the pod specification for ephemeral use cases. They can be used to inject arbitrary states, such as configuration, secrets, identity, variables or similar information, directly inside pods using a mounted volume. This was initially introduced in 1.15 as an alpha feature, and it moved to GA. This feature is used by some CSI drivers such as the [secret-store CSI driver](https://github.com/kubernetes-...