message LifecycleHandler {
  // Exec specifies the action to take.
  // +optional
  optional ExecAction exec = 1;

  // HTTPGet specifies the http request to perform.
  // +optional
  optional HTTPGetAction httpGet = 2;

  // Deprecated. TCPSocket is NOT supported as a LifecycleHandler and kept
  // for the backward compatibility. There are no validation of this field and

join` only did the discovery part and exited successfully without checking that the kubelet actually started properly and performed the TLS bootstrap correctly. Now, as kubeadm runs some post-join steps (for example, annotating the Node API object with the CRISocket), `kubeadm join` is now waiting for the kubelet to perform the TLS Bootstrap, and then uses that credential to perform further actions. This also improves the UX, as `kubeadm` will exit with a non-zero code if the kubelet isn't in a functional...

  - true/strict - perform validation and error the request on any invalid fields in the ojbect. It will attempt to perform server-side validation if it is enabled on the apiserver, otherwise it will fall back to client-side validation.

- From now on, the HPA controller will return an error for the container resource metrics when the feature gate `HPAContainerMetrics` is disabled. As a result, HPA with a container resource metric performs no scale-down and performs only. ([#116043](https://github.com/kubernetes/kubernetes/pull/116043), [@sanposhiho](https://github.com/sanposhiho))

documented behavior). In this case an event with reason "ProbeWarning" will be generated, indicating that the redirect was ignored. If you were previously relying on the redirect to run health checks against different endpoints, you will need to perform the healthcheck logic outside the Kubelet, for instance by proxying the external endpoint rather than redirecting to it. ([#75416](https://github.com/kubernetes/kubernetes/pull/75416), [@tallclair](https://github.com/tallclair))

- client-go...

  * The Docker-CRI implementation is enabled by default.
  * It is not compatible with containers created by older Kubelets. It is
    recommended to drain your node before upgrade. If you choose to perform
    an in-place upgrade, the Kubelet will automatically restart all
    Kubernetes-managed containers on the node.
  * It is not compatible with CNI plugins that do not conform to the

### Introducing Windows CSI support alpha for Kubernetes

With the release of Kubernetes 1.18, an alpha version of CSI Proxy for Windows is getting released. CSI proxy enables non-privileged (pre-approved) containers to perform privileged storage operations on Windows. CSI drivers can now be supported in Windows by leveraging CSI proxy.
SIG Storage made a lot of progress in the 1.18 release.

- Kubeadm: during execution of the "check expiration" command, treat the etcd CA as external if there is a missing etcd CA key file (etcd/ca.key) and perform the proper validation on certificates signed by the etcd CA. Additionally, make sure that the CA for all entries in the output table is included - for both certificates on disk and in kubeconfig files. ([#106924](https://github.com/kubernetes/kub...

* Fix GCE etcd scripts to pass in all required parameters for the etcd migration utility to correctly perform HA upgrades and downgrades ([#61957](https://github.com/kubernetes/kubernetes/pull/61957), [@jpbetz](https://github.com/jpbetz))

 - There is a new OCI image registry (`registry.k8s.io`) that can be used to pull Kubernetes images. The old registry (`k8s.gcr.io`) will continue to be supported for the foreseeable future, but the new name should perform better because it frontends equivalent mirrors in other clouds.  Please point your clusters to the new registry going forward. \n\nAdmission/Policy integrations that have an allowlist of registries need to include `registry.k8s.io` alongside `k8s...