- Kubeadm: perform pre-flight validation on host/node name upon `kubeadm init` and `kubeadm join`, showing warnings on non-compliant names ([#99194](https://github.com/kubernetes/kubernetes/pull/99194), [@pacoxu](https://github.com/pacoxu))

    - [Client Binaries](#client-binaries-11)
    - [Server Binaries](#server-binaries-11)
    - [Node Binaries](#node-binaries-11)
  - [1.9 Release Notes](#19-release-notes)
  - [WARNING: etcd backup strongly recommended](#warning-etcd-backup-strongly-recommended)
  - [Introduction to 1.9.0](#introduction-to-190)
  - [Major themes](#major-themes)
    - [API Machinery](#api-machinery)
    - [Apps](#apps)
    - [Auth](#auth)

  When an Indexed Job has a number of completions higher than 10^5 and parallelism higher than 10^4, and a big number of Indexes fail, Kubernetes might not be able to track the termination of the Job. Kubernetes now emits a warning, at Job creation, when the Job manifest exceeds both of these limits. ([#118420](https://github.com/kubernetes/kubernetes/pull/118420), [@alculquicondor](https://github.com/alculquicondor)) [SIG Apps]

## Changes by Kind

### Deprecation

- Added a [warning](https://k8s.io/blog/2020/09/03/warnings/) response when handling requests that set the deprecated `spec.externalID` field for a Node. ([#115944](https://github.com/kubernetes/kubernetes/pull/115944), [@SataQiu](https://github.com/SataQiu)) [SIG Node]
- Added warnings to the Services API. Kubernetes now warns for Services in the case of:

  - The `--experimental-encryption-provider-config` flag is deprecated in favor of `--encryption-provider-config`. The old flag is accepted with a warning but will be removed in 1.14. ([#71206](https://github.com/kubernetes/kubernetes/pull/71206),...

  Don't use these flags. Using deprecated flags causes the server to print a warning. Using a removed flag causes the server to abort the startup.

* The following deprecated flags were removed from `kubelet`:

  * `api-servers` - add apiserver addresses to the kubeconfig file instead.

  Don't use these flags. Using deprecated flags causes the kubelet to print a warning. Using a removed flag causes the kubelet to abort the startup.

* GCE: A role and clusterrole will now be provided with GCE/GKE for allowing the cloud-provider to post warning events on all services and watching configmaps in the kube-system namespace. No user action is required. ([#59686](https://github.com/kubernetes/kubernetes/pull/59686), [@nicksardo](https://github.com/nicksardo))

- Warning about using a deprecated volume plugin is logged only once. ([#96751](https://github.com/kubernetes/kubernetes/pull/96751), [@jsafrane](https://github.com/jsafrane)) [SIG Storage]

### Other (Cleanup or Flake)

5. If the PR is unfinished, see how to mark it: https://git.k8s.io/community/contributors/guide/pull-requests.md#marking-unfinished-pull-requests
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For new clusters if you have not configured the cgroup driver explicitly you might get a failure in the `kubelet` on driver mismatch (kubeadm clusters should be using the `systemd` driver). Also remove the `IsDockerSystemdCheck` preflight check (warning) that checks if the Docker cgroup driver is set to `systemd`. Ideally such detection / coordination should be on the side of CRI implementers and the kubelet (tracked [here](https://github.com/kubernetes/kubernetes/issues/99808)). Please see the ...