Custom resource definitions are now available and have been improved with pruning, defaulting, and OpenAPI publishing.

As an extensibility mechanism, admission plugins can be developed as extensions and can now be run as webhooks configured at runtime.

A global metrics registry has been implemented to register metrics to be exposed in a more transparent means.

The Container Storage Interface (CSI) has been further improved to help migrate in-tree volume plugins to the CSI.

Certificate management is more robust with kubeadm seamlessly rotating all certificates (on upgrades) before they expire.

There are now improvements for scheduling nodes by using items such as schedule daemon set pods, taint nodes by condition, and node lease.

The kubectl get and kubectl describe commands now work with Kubernetes API extensions.

The kubectl convert command has been removed.

Pod security policy resources have been changed from the extensions/v1beta1 API to the policy/v1beta1 API. Existing persisted data can be retrieved via the policy/v1beta1 API.

Network policy resources have been changed from the extensions/v1beta1 API to the networking.k8s.io/v1 API. Existing persisted data can be retrieved via the networking.k8s.io/v1 API.

The daemon set, deployment, and replica set resources have been changed from the extensions/v1beta1, apps/v1beta1, or apps/v1beta2 APIs to the apps/v1 API. Existing persisted data can be retrieved via the apps/v1 API.

Priority class resources have been changed from the scheduling.k8s.io/v1beta1 and scheduling.k8s.io/v1alpha1 APIs to the scheduling.k8s.io/v1 API. Existing persisted data can be retrieved via the scheduling.k8s.io/v1 API.