- `PriorityLevelConfiguration`: the `.spec.limited.nominalConcurrencyShares` field defaults to `30` only if the field is omitted (v1beta3 also defaulted an explicit `0` value to `30`). Specifying an explicit `0` value is not allowed in the `v1` version in v1.29 to ensure compatibility with `v1.28` API servers. In `v1.30`, explicit `0` values will be allowed in this field in the `v1` API.

 - Kubeadm: during "init" an empty cgroupDriver value in the KubeletConfiguration is now always set to "systemd" unless the user is explicit about it. This requires existing machine setups to configure the container runtime to use the "systemd" driver. Documentation on this topic can be found here: https://kubernetes.io/docs/setup/production-environment/container-runtimes/. When upgrading...

- Zero-value `metadata.creationTimestamp` values are now omitted and no longer serialize an explicit `null` in JSON, YAML, and CBOR output ([#130989](https://github.com/kubernetes/kubernetes/pull/130989), [@liggitt](https://github.com/liggitt)) [SIG API Machinery, Apps, Architecture, Auth, CLI, Cloud Provider, Cluster Lifecycle, Etcd, Instrumentation,...

- Kubeadm: during "kubeadm init/join/upgrade", always default the `cgroupDriver` value in the `KubeletConfiguration` to `systemd`, unless the user was explicit about the value. See [configure-cgroup-driver](https://kubernetes.io/docs/tasks/administer-cluster/kubeadm/configure-cgroup-driver/) for more details. ([#102133](https://github.com/kubernetes/kubernetes/pull/102133), [@pacoxu](https://github.com/pacoxu))...

- client-go
  - The deprecated versionless API group accessors (like `clientset.Apps()`) have been removed. Use an explicit version instead (like `clientset.AppsV1()`) ([#74422](https://github.com/kubernetes/kubernetes/pull/74422), [@liggitt](https://github.com/liggitt))

- Added new -f flag into debug command to be used passing pod or node files instead explicit names. ([#111453](https://github.com/kubernetes/kubernetes/pull/111453), [@ardaguclu](https://github.com/ardaguclu))

No Known Issues Reported

## Urgent Upgrade Notes

### (No, really, you MUST read this before you upgrade)

#### kube-apiserver:
- in an `--encryption-provider-config` config file, an explicit `cacheSize: 0` parameter previously silently defaulted to caching 1000 keys. In Kubernetes 1.18, this now returns a config validation error. To disable caching, you can specify a negative cacheSize value in Kubernetes 1.18+.

* bump(golang.org/x/oauth2): a6bd8cefa1811bd24b86f8902872e4e8225f74c4 ([#45056](https://github.com/kubernetes/kubernetes/pull/45056), [@ericchiang](https://github.com/ericchiang))
* apimachinery: make explicit that meta.KindToResource is only a guess ([#45272](https://github.com/kubernetes/kubernetes/pull/45272), [@sttts](https://github.com/sttts))

* Fix incorrect retry logic in scheduler ([#50106](https://github.com/kubernetes/kubernetes/pull/50106), [@julia-stripe](https://github.com/julia-stripe))
* Enforce explicit references to API group client interfaces in clientsets to avoid ambiguity. ([#49370](https://github.com/kubernetes/kubernetes/pull/49370), [@sttts](https://github.com/sttts))

*   deviceplugin has been extended to more gracefully handle the full device plugin lifecycle, including: ([#55088](https://github.com/kubernetes/kubernetes/pull/55088),[ @jiayingz](https://github.com/jiayingz))
    *   Kubelet now uses an explicit cm.GetDevicePluginResourceCapacity() function that makes it possible to more accurately determine what resources are inactive and return a more accurate view of available resources.