- The in-tree GCE PD plugin `kubernetes.io/gce-pd` is now deprecated and will be removed in 1.21. Users that self-deploy Kubernetes on GCP should enable CSIMigration + CSIMigrationGCE features and install the GCE PD CSI Driver (https://github.com/kubernetes-sigs/gcp-compute-persistent-disk-csi-driver) to avoid disruption to existing Pod and PVC objects at that time. Users should start using the GCE PD CSI CSI Driver directly for any new volumes. ([#85231](https://github.com/kuberne...

feature, you might need to take some action immediately after upgrading. In multi-tenant clusters where not all users are trusted, you are advised to create appropriate quotas for two default priority classes, system-cluster-critical and system-node-critical, which are added to clusters by default. `ResourceQuota` should be created to limit users from creating Pods at these priorities if not all users of your cluster are trusted. We do not advise disabling this feature because critical system Pods rely on...

- Removed a warning around Linux user namespaces and kernel version. If the feature gate `UserNamespacesSupport` was enabled, the kubelet previously warned when detecting a Linux kernel version earlier than 6.3.0. User namespace support on Linux typically does still need kernel 6.3 or...

- Kubectl: Previously users cannot provide arguments to a external diff tool via KUBECTL_EXTERNAL_DIFF env. This release now allow users to specify args to KUBECTL_EXTERNAL_DIFF env. ([#95292](https://github.com/kubernetes/kubernetes/pull/95292), [@dougsland](https://github.com/dougsland)) [SIG CLI]

- Kubeadm: graduate the command `kubeadm alpha kubeconfig user` to `kubeadm kubeconfig user`. The `kubeadm alpha kubeconfig user` command is deprecated now. ([#97583](https://github.com/kubernetes/kubernetes/pull/97583), [@knight42](https://github.com/knight42)) [SIG Cluster Lifecycle]

### CSI Migration updates

CSI Migration enables the replacement of existing in-tree storage plugins such as `kubernetes.io/gce-pd` or `kubernetes.io/aws-ebs` with a corresponding CSI driver.
If CSI Migration is working properly, Kubernetes end users shouldn’t notice a difference.

* The `--authorization-rbac-super-user` flag (alpha in 1.5) is deprecated; the `system:masters` group has privileged access ([#38121](https://github.com/kubernetes/kubernetes/pull/38121), [@deads2k](https://github.com/deads2k))

flag from `kubelet` command line. For `non-kubeadm` clusters, users must manually remove this flag from their `kubelet` configuration to prevent startup failures before upgrading `kubelet`. For `kubeadm` clusters, if users pass extra arguments to the `kubelet` like `--pod-infra-container-image`, it will be written to the `kubelet` env file during the `init` phase. `kubeadm` does not remove it during the `init` or `join` phase, so users must manually remove it from `extraArgs` in the `kubelet` configuration...

* Kubernetes version command line parameter in kubeadm has been updated to drop an unnecessary redirection from ci/latest.txt to ci-cross/latest.txt. Users should know exactly where the builds are stored on Google Cloud storage buckets from now on. For example for 1.9 and 1.10, users can specify ci/latest-1.9 and ci/latest-1.10 as the CI build jobs what build images correctly updates those. The CI jobs for master update the ci-cross/latest location, so if you are...

- Adds feature gate `KubeletInUserNamespace` which enables support for running kubelet in a user namespace.
  
  The user namespace has to be created before running kubelet.
  All the node components such as CRI need to be running in the same user namespace.