you must keep the following in mind:

* **JSON configuration files that contain fields with incorrect case will no longer be valid. You must correct these files before upgrading.** When specifying keys in JSON resource definitions during direct API server communication, the keys are case-sensitive. A bug introduced in Kubernetes 1.8 caused the API server to accept a request with incorrect case and coerce it to correct case, but this behaviour has been fixed in 1.11 and the API server...

- Kubeadm: warn but do not error out on missing "ca.key" files for root CA, front-proxy CA and etcd CA, during "kubeadm join --control-plane" if the user has provided all certificates, keys and kubeconfig files which require signing with the given CA keys. ([#94988](https://github.com/kubernetes/kubernetes/pull/94988), [@neolit123](https://github.com/neolit123)) [SIG Cluster Lifecycle]

### Other (Cleanup or Flake)

    * If you are running E2E tests which require SSH keys and you utilize environment variables to override their location, you may need to modify the environment variable set. On all providers the environment variable override can now be either an absolute path to the key or a relative path (relative to ~/.ssh). Specifically the changes are:
    *  - Created new GCE_SSH_KEY allowing specification of SSH keys for gce, gke, and kubemark.

- Fixed a regression in default configurations, which enabled PodDisruptionConditions by default, 
  that prevented the control plane's pod garbage collector from deleting pods that contained duplicated field keys (env. variables with repeated keys or container ports). ([#121380](https://github.com/kubernetes/kubernetes/pull/121380), [@mimowo](https://github.com/mimowo)) [SIG Apps, Auth, Scheduling and Testing]

- kubeadm still generates RSA keys when deploying a node, but also accepts ECDSA
keys if they already exist in the directory specified in the `--cert-dir` option. ([#76390](https://github.com/kubernetes/kubernetes/pull/76390), [@rojkov](https://github.com/rojkov))

- Kube-apiserver: Fixed a `v1.34` regression with spurious "Error getting keys" log messages. ([#133817](https://github.com/kubernetes/kubernetes/pull/133817), [@serathius](https://github.com/serathius)) [SIG API Machinery and Etcd]

- Kubeadm now warns (instead of error out) on missing "ca.key" files for root CA, front-proxy CA and etcd CA, during "kubeadm join --control-plane" if the user has provided all certificates, keys and kubeconfig files which require signing with the given CA keys. ([#94988](https://github.com/kubernetes/kubernetes/pull/94988), [@neolit123](https://github.com/neolit123))

### ConfigMap
* Volumes and environment variables populated from ConfigMap and Secret objects can now tolerate the named source object or specific keys being missing, by adding `optional: true` to the volume or environment variable source specifications. ([#39981](https://github.com/kubernetes/kubernetes/pull/39981), [@fraenkel](https://github.com/fraenkel))

if (x == T{a,b,c}[i]) { … }
</pre>

<h4>Struct literals</h4>

<p>
For struct literals without keys, the element list must contain an element
for each struct field in the order in which the fields are declared.
</p>

<p>
For struct literals with keys the following rules apply:
</p>
<ul>
	<li>Every element must have a key.
	</li>

  
  When the feature gate is enabled, kubelet ignores errors that happens during setting the following sysctl values: `vm.overcommit_memory`, `vm.panic_on_oom`, `kernel.panic`, `kernel.panic_on_oops`, `kernel.keys.root_maxkeys`, `kernel.keys.root_maxbytes`. (These sysctl values for the host, not for the containers)
  
  kubelet also ignores an error during opening `/dev/kmsg`.