- Kubeadm: added the experimental (alpha) feature gate `EtcdLearnerMode` that allows etcd members to be joined as learner and only then promoted as voting members ([#113318](https://github.com/kubernetes/kubernetes/pull/113318), [@pacoxu](https://github.com/pacoxu))

9328), [@divyenpatel](https://github.com/divyenpatel))

* Emit number of bound and unbound persistent volumes as Metrics. This PR adds four kinds of Volume Metrics for kube-controller-manager: bound PVC numbers, unbound PVC numbers, bound PV numbers and unbound PV numbers. The PVC metrics use namespace as dimension and the PV metrics use StorageClassName as its dimension. With these metrics we can better monitor the use of volumes in the cluster. ([#57872](https://github.com/kubernet...

* Add automatic etcd 3.2->3.1 and 3.1->3.0 minor version rollback support to gcr.io/google_container/etcd images. For HA clusters, all members must be stopped before performing a rollback. ([#59298](https://github.com/kubernetes/kubernetes/pull/59298), [@jpbetz](https://github.com/jpbetz))

- Kubeadm: fix a bug where "kubeadm join" would not properly handle missing names for existing etcd members. ([#97372](https://github.com/kubernetes/kubernetes/pull/97372), [@ihgann](https://github.com/ihgann)) [SIG Cluster Lifecycle]

- Kubeadm: apply further improvements to the tentative support for concurrent etcd member join. Fixes a bug where multiple members can receive the same hostname. Increase the etcd client dial timeout and retry timeout for add/remove/... operations. ([#87505](https://github.com/kubernetes/kubernetes/pull/87505), [@neolit123](https://github.com/neolit123)) [SIG...

- Kubeadm: apply further improvements to the tentative support for concurrent etcd member join. Fixes a bug where multiple members can receive the same hostname. Increase the etcd client dial timeout and retry timeout for add/remove/... operations. ([#87505](https://github.com/kubernetes/kubernetes/pull/87505), [@neolit123](https://github.com/neolit123)) [SIG...

[Setup topics]: https://kubernetes.io/docs/setup/pick-right-solution/
[SIGs]: https://github.com/kubernetes/community/blob/master/sig-list.md


## Major Themes

Kubernetes is developed by community members whose work is organized into
[Special Interest Groups][]. For the 1.8 release, each SIG provides the
themes that guided their work.

- Kubeadm init phase certs now support the `--csr-only` option, simplifying custom CA creation.
- `kubeadm join --experimental-control-plane` now automatically adds a new etcd member for `local etcd` mode, further simplifying required tasks for HA clusters setup.
- Improvements were made to `kubeadm reset` related to cleaning  etcd and notifying the user about the state of iptables.

* fixes a memory leak in the kube-controller-manager observed when large numbers of pods with tolerations are created/deleted ([#65339](https://github.com/kubernetes/kubernetes/pull/65339), [@liggitt](https://github.com/liggitt))

### SIG-ibmcloud

As a newly created SIG, the SIG-ibmcloud has mainly focused on SIG set up, sharing IBM Clouds ongoing Kubernetes work like scalability tests, Kubernetes upgrade strategy etc. with the SIG members and start working on processes to move cloud provider code to a public GitHub repo.

### SIG-instrumentation

No feature work, but a large refactoring of metrics-server as well as a number of bug fixes.