* Pod priority and preemption is now enabled by default. Even if you don't plan to use this feature, you might need to take some action immediately after upgrading. In multi-tenant clusters where not all users are trusted, you are advised to create appropriate quotas for two default priority classes, system-cluster-critical and system-node-critical, which are added to clusters by default. `ResourceQuota` should be created to limit users from creating Pods at these priorities...

([#58171](https://github.com/kubernetes/kubernetes/pull/58171), [@verult](https://github.com/verult))

* Default values differ between the Kubelet's componentconfig (config file) API and the Kubelet's command line. Be sure to review the default values when migrating to using a config file. For example, the authz mode is set to "AlwaysAllow" if you rely on the command line, but defaults to the more secure "Webhook" mode if you load config from a file. ([#59666](https://github.com/kubernetes/ku...

- Feature gates CSIMigration to Beta (on by default) and CSIMigrationGCE to Beta (off by default since it requires installation of the GCE PD CSI Driver) ([#85231](https://github.com/kubernete...

 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
 `--token-ttl 0` to `kubeadm init`. The default token can later be deleted with
 `kubeadm token delete`.

    *   Clients using older endpoints will be unaffected. This change is only at the REST API level and is independent of the default behavior of particular clients (e.g. this does not affect the default for the kubectl `--cascade` flag).
    *   If you upgrade your client-go libs and use the `AppsV1()` interface, please note that the default garbage collection behavior is changed.

### **Auth**

#### **Audit**

- The RemoteRequestHeaderUID feature moves to beta and is now enabled by default. This makes the kube-apiserver propagate UIDs in the `X-Remote-Uid` header in requests to the aggregated API servers. The header is not honored by default for incoming requests, but that can be enabled by setting...

- Kube-apiserver: fixes a 1.27+ regression in watch stability by serving watch requests without a resourceVersion from the watch cache by default, as in <1.27 (disabling the change in #115096 by default). This mitigates the impact of an etcd watch bug (https://github.com/etcd-io/etcd/pull/17555). If the 1.27 change in #115096 to serve these requests from underlying storage is still desired despite the impact on watch...

  
  $ kubectl describe pod xxx
  ......
  Events:
    Type    Reason     Age        From               Message
    ----    ------     ----       ----               -------
    Normal  Scheduled  <unknown>  default-scheduler  Successfully assigned default/nginx-6c975b59f8-gvmjr to minikube
  ......

    * ServiceDelimiter string Delimiter to use to separate overridden services (multiple services) Defaults to "&"
    * ServicenameDelimiter string Delimiter to use to separate servicename from its configuration parameters Defaults "|"
    * OverrideSeparator string Delimiter to use to separate region of occurrence, url and signing region for each override Defaults to ","

### Volumes
* StorageClass pre-installed and set as default on Azure, AWS, GCE, OpenStack, and vSphere.
  * This is something to pay close attention to if you’ve been using Kubernetes for a while, because it changes the default behavior of PersistentVolumeClaim objects on these clouds.