* kube-apiserver: The external hostname no longer longer use the cloud provider API to select a default. It can be set explicitly using --external-hostname, if needed. If there is no default, AdvertiseAddress or os.Hostname() will be used, in that order. ([#56812](https://github.com/kubernetes/kubernetes/pull/56812), [@dims](https://github.com/dims))

*   The kubeadm `--skip-preflight-checks` flag is now deprecated and will be removed in a future release.
*   If you are using the cloud provider API to determine the external host address of the apiserver, set `--external-hostname` explicitly instead. The cloud provider detection has been deprecated and will be removed in the future ([#54516](https://github.com/kubernetes/kubernetes/pull/54516),[ @dims](https://github.com/dims))

### **Multicluster**

- `StatefulSet` names must be DNS labels, rather than subdomains. Any `StatefulSet`
  which took advantage of subdomain validation (by having dots in the name) can't
  possibly have worked, because we eventually set `pod.spec.hostname` from the `StatefulSetName`,
  and that is validated as a DNS label. ([#114172](https://github.com/kubernetes/kubernetes/pull/114172), [@thockin](https://github.com/thockin))

- Fix isCurrentInstance for Windows by removing the dependency of hostname. ([#89138](https://github.com/kubernetes/kubernetes/pull/89138), [@feiskyer](https://github.com/feiskyer)) [SIG Cloud Provider]

## Changelog since v1.8.1

### Other notable changes

* Allow for configuring etcd hostname in the manifest ([#54403](https://github.com/kubernetes/kubernetes/pull/54403), [@wojtek-t](https://github.com/wojtek-t))

### SIG Network

- Corrected family type (inet6) for ipsets in ipv6-only clusters ([#68436](https://github.com/kubernetes/kubernetes/pull/68436), [@uablrek](https://github.com/uablrek))
- kube-proxy argument `hostname-override` can be used to override hostname defined in the configuration file ([#69340](https://github.com/kubernetes/kubernetes/pull/69340), [@stevesloka](https://github.com/stevesloka))

  qualified domain name (FQDN) of a Pod is set as hostname of its containers. 
  In Linux containers, this means setting the FQDN in the hostname field of the 
  kernel (the nodename field of struct utsname).  In Windows containers, this
  means setting the this means setting the registry value of hostname for the registry key HKEY_LOCAL_MACHINE\\SYSTEM\\CurrentControlSet\\Services\\Tcpip\\Parameters to FQDN. 

    - [<code>kubectl debug</code> graduates to Beta](#kubectl-debug-graduates-to-beta)
    - [Removing deprecated flags in kubeadm](#removing-deprecated-flags-in-kubeadm)
    - [Pod Hostname as FQDN graduates to Beta](#pod-hostname-as-fqdn-graduates-to-beta)
    - [<code>TokenRequest</code> / <code>TokenRequestProjection</code> graduates to General Availability](#tokenrequest--tokenrequestprojection-graduates-to-general-availability)

- Node Problem Detector is now available for GCE Windows nodes. ([#101539](http...

   ([#121834](https://github.com/kubernetes/kubernetes/pull/121834), [@vaibhav2107](https://github.com/vaibhav2107))
- Changed the API server so that for admission webhooks that have a URL matching the hostname 'localhost' or a loopback IP address, the connection supports HTTP/2 where it could be negotiated.
   ([#122558](https://github.com/kubernetes/kubernetes/pull/122558), [@linxiulei](https://github.com/linxiulei))