- Kubeadm: fixed a bug when using `kubeadm init --dry-run` with certificate authority files (`ca.key` / `ca.crt`) present in `/etc/kubernetes/pki`) ([#108410](https://github.com/kubernetes/kubernetes/pull/108410), [@Haleygo](https://github.com/Haleygo))

## WARNING: etcd backup strongly recommended

Before updating to 1.6, you are strongly recommended to back up your etcd data.
Please consult the installation procedure you are using (kargo, kops, kube-up,
kube-aws, kubeadm etc) for specific advice.

1.6 encourages etcd3, and switching from etcd2 to etcd3 involves a full
migration of data between different storage engines.  You must stop the API

- **Cluster Lifecycle**

- Kubeadm: fixed a bug during kubeadm upgrade, where it is not possible to mount a new device and create a symbolic link for /etc/kubernetes (or a sub-directory) so that kubeadm stores its information on the mounted device. ([#123406](https://github.com/kubernetes/kubernetes/pull/123406), [@SataQiu](https://github.com/SataQiu))

  * A new field hostAliases has been added to the pod spec to support [adding entries to a Pod's /etc/hosts file](https://kubernetes.io/docs/concepts/services-networking/add-entries-to-pod-etc-hosts-with-host-aliases/). ([#44641](https://github.com/kubernetes/kubernetes/pull/44641), [@rickypai](https://github.com/rickypai))

- The new test `[sig-network] DNS should now provide /etc/hosts entries for the cluster [LinuxOnly] [Conformance]` will validate the host entries set in the ``/etc/hosts`` file (pod's FQDN and hostname), which should be managed by Kubelet. ([#72729](https://github.com/kubernetes/kubernetes/pull/72729), [@bclau](https://github.com/bclau))

- Kubeadm: fix panic in the command "kubeadm certs check-expiration" when "/etc/kubernetes/pki" exists but cannot be read. ([#124124](https://github.com/kubernetes/kubernetes/pull/124124), [@carlory](https://github.com/carlory)) [SIG Cluster Lifecycle]

- Finalizer Protection...

- Kubeadm: added the "--cleanup-tmp-dir" flag for `kubeadm reset`. It will cleanup the contents of `/etc/kubernetes/tmp`. The flag is off by default. ([#112172](https://github.com/kubernetes/kubernetes/pull/112172), [@chendave](https://github.com/chendave))

* Add support for 3rd party objects to kubectl ([#18835](https://github.com/kubernetes/kubernetes/pull/18835), [@brendandburns](https://github.com/brendandburns))
* Remove unnecessary override of /etc/init.d/docker on containervm image. ([#23593](https://github.com/kubernetes/kubernetes/pull/23593), [@dchen1107](https://github.com/dchen1107))