- Kubeadm: fix the bug that 'kubeadm upgrade' hangs in single node cluster ([#88434](https://github.com/kubernetes/kubernetes/pull/88434), [@SataQiu](https://github.com/SataQiu)) [SIG Cluster Lifecycle]
- Kubeadm: make sure images are pre-pulled even if a tag did not change but their contents changed ([#85603](https://github.com/kubernetes/kubernetes/pull/85603), [@bart0sh](https://github.com/bart0sh)) [SIG Cluster Lifecycle]

  `--resource-container`, `--system-container`, `--reconcile-cidr`
* Remove the temporary fix for pre-1.0 mirror pods. Upgrade directly from
  pre-1.0 to 1.6 kubelet is not supported.
* Fluentd was migrated to Daemon Set, which targets nodes with
  beta.kubernetes.io/fluentd-ds-ready=true label. If you use fluentd in your
  cluster please make sure that the nodes with version 1.6+ contains this
  label.

### kubectl

- When using IPV6-only, be sure to use `proxy-mode=iptables` as `proxy-mode=ipvs` is known to not work. ([#68437](https://github.com/kubernetes/kubernetes/issues/68437))

## Deprecations

- kube-apiserver

For more information, see [#53288](https://issue.k8s.io/53288).

* `kubeadm init` and `kubeadm join` invocations on newly installed systems can encounter a `/var/lib/kubelet is not empty` message during pre-flight checks that prevents setup. If this is the only pre-flight failure, it can be safely ignored with `--skip-preflight-checks`.

For more information, see [#53356](https://issue.k8s.io/53356#issuecomment-333748618).

 - [Action Required] CSI drivers that call IsLikelyNotMountPoint should not assume false means that the path is a mount point. Each CSI driver needs to make sure correct usage of return value of IsLikelyNotMountPoint because if the file is an irregular file but not a mount point is acceptable ([#129370](https://github.com/kubernetes/kubernetes/pull/129370), [@andyzhangx](https://github.com/andyzhangx)) [SIG...

- Remove rescheduler since scheduling DS pods by default scheduler is moving to beta. ([#67687](https://github.com/kubernetes/kubernetes/pull/67687), [@Lion-Wei](https://github.com/Lion-Wei))
- kubeadm: make sure pre-pulled kube-proxy image and the one specified in its daemon set manifest are the same ([#67131](https://github.com/kubernetes/kubernetes/pull/67131), [@rosti](https://github.com/rosti))

* kubeadm: clean up exited containers and network checkpoints ([#43836](https://github.com/kubernetes/kubernetes/pull/43836), [@yujuhong](https://github.com/yujuhong))
* ActiveDeadlineSeconds is validated in workload controllers now, make sure it's not set anywhere (it shouldn't be set by default and having it set means your controller will restart the Pods at some point) ([#38741](https://github.com/kubernetes/kubernetes/pull/38741), [@sandflee](https://github.com/sandflee))

uses the _structured parameters_ model (also alpha) for allocating dynamic resources to Pods.

  if and only if classic DRA was enabled in a cluster, remove all workloads (pods, app deployments, etc. ) which depend on classic DRA and make sure that all PodSchedulingContext resources are gone before upgrading. PodSchedulingContext resources cannot be removed through the apiserver after an upgrade and workloads would not work properly. ([#128003](https://github.com/kubernetes/kubernetes/pull/128003),...

### **Network**

*   NetworkPolicy objects are now stored in etcd in v1 format. After you upgrade to version 1.9, make sure that all NetworkPolicy objects are migrated to v1. ([#51955](https://github.com/kubernetes/kubernetes/pull/51955), [@danwinship](https://github.com/danwinship))

* The minimum supported version of Docker is now 1.11; if you are using Docker 1.10 or below, be sure to upgrade Docker before upgrading Kubernetes. ([#57845](https://github.com/kubernetes/kubernetes/pull/57845), [@yujuhong](https://github.com/yujuhong))