that need to run prior to the network being ready.
* **Enhance Kubelet QoS**:
  * Pods are placed under a new cgroup hierarchy by default. This feature requires
    draining and restarting the node as part of upgrades. To opt-out set
    `--cgroups-per-qos=false`.
  * If `kube-reserved` and/or `system-reserved` are specified, node allocatable

- The calculation of pod UIDs for static pods has changed to ensure each static pod gets a unique value - this will cause all static pod containers to be recreated/restarted if an in-place kubelet upgrade from 1.20 to 1.21 is performed. Note that draining pods before upgrading the kubelet across minor versions is the supported upgrade path. ([#87461](https://github.com/kubernetes/kubernetes/pull/87461), [@bboreham](https://github.com/bboreham)) [SIG Node]

- 'Container `preStop` and `postStart` lifecycle handlers using `httpGet` now
  honor the specified `scheme` and `headers` fields. This enables setting custom
  headers and changing the scheme to `HTTPS`, consistent with container
  startup/readiness/liveness probe capabilities. Lifecycle handlers configured
  with `scheme: HTTPS` that encounter errors indicating the endpoint is actually

- Fix indexer bug that resulted in incorrect index updates if number of index values for a given object was changing during update ([#109137](https://github.com/kubernetes/kubernetes/pull/109137), [@wojtek-t](https://github.com/wojtek-t)) [SIG API Machinery]

 - Insert a debug container in clusters that don’t have ephemeral containers enabled 
 - Modify a crashing container for easier debugging by changing its image, for example to busybox, or its command, for example, to `sleep 1d` so you have time to `kubectl exec`.
 - Inspect configuration files on a node's host filesystem