- kubeadm: if an unknown command name is passed to any parent command such as 'kubeadm init phase' return an error. If 'kubeadm init phase' or another command that has subcommands is called without subcommand name, print the available commands and also return an error. ([#127096](https://github.com/kubernetes/kubernetes/pull/127096), [@neolit123](https://github.com/neolit123)) [SIG Cluster Lifecycle]

    - [Garbage Collector](#garbage-collector)
    - [kubeadm](#kubeadm-2)
    - [kubectl](#kubectl-1)
      - [New Commands](#new-commands)
      - [Create subcommands](#create-subcommands)
      - [Updates to existing commands](#updates-to-existing-commands)
      - [Updates to apply](#updates-to-apply)
      - [Updates to edit](#updates-to-edit)
      - [Bug fixes](#bug-fixes)

  that provide new subcommands. Refer to the documentation for more information.

- `kubectl rollout` and `rollback` now support StatefulSet.

- `kubectl scale` now uses the Scale subresource for kinds in the apps/v1beta2 group.

- `kubectl create configmap` and `kubectl create secret` subcommands now support

- Changed `kubectl help` to display basic details for subcommands from plugins. ([#116752](https://github.com/kubernetes/kubernetes/pull/116752), [@xvzf](https://github.com/xvzf))

- Added a `--show-swap` option to `kubectl top` subcommands ([#129458](https://github.com/kubernetes/kubernetes/pull/129458), [@iholder101](https://github.com/iholder101)) [SIG CLI]

    *   Make crictl command more user friendly and add more subcommands.
    *   Integrate with CRI verbose option to provide extra debug information.
    *   Update CRI to kubernetes v1.9.
    *   Bug fixes in validation test suites.

- The  command line option  --cri-socket-path of the kubeadm subcommand "kubeadm config images pull" has been renamed to --cri-socket to be consistent with the rest of kubeadm subcommands.

- `kubectl run` has removed the previously deprecated generators, along with flags unrelated to creating pods. `kubectl run` now only creates pods. See specific `kubectl create` subcommands to create objects other than pods. 
([#87077](https://github.com/kubernetes/kubernetes/pull/87077), [@soltysh](https://github.com/soltysh)) [SIG Architecture, CLI and Testing]

Updated Plugin Mechanism for kubectl is Graduating to Stable ([#579](https://github.com/kubernetes/enhancements/issues/579))

- Extends functionality to kubectl to support extensions adding new commands as well as overriding specific subcommands (at any depth).
- Documentation fixes
kubernetes/enhancements: [#579](https://github.com/kubernetes/enhancements/issues/579) [[kep](https://github.com/kubernetes/enhancements/blob/master/keps/sig-cli/0024-kubectl-plugins.md#summary)]

- Enable external plugins can be used as subcommands for kubectl create command if subcommand does not exist as builtin only when KUBECTL_ENABLE_CMD_SHADOW environment variable is exported. ([#116293](https://github.com/kubernetes/kubernetes/pull/116293), [@ardaguclu](https://github.com/ardaguclu))