([#44744](https://github.com/kubernetes/kubernetes/pull/44744), [@yguo0905](https://github.com/yguo0905))

  * Kubernetes now shares a single PID namespace among all containers in a pod when running with docker >= 1.13.1. This means processes can now signal processes in other containers in a pod, but it also means that the `kubectl exec {pod} kill 1` pattern will cause the Pod to be restarted rather than a single container. ([#45236](https://github.com/kubernetes/kubernetes/pull/45236), [@verb](...

for COS images on GCE has changed to `/home/kubernetes/flexvolume`, rather than `/etc/srv/kubernetes/kubelet-plugins/volume/exec`. Existing Flexvolume installations in clusters using COS images must be moved to the new directory, and installation processes must be updated with the new path. ([#58171](https://github.com/kubernetes/kubernetes/pull/58171), [@verult](https://github.com/verult))

* Default values differ between the Kubelet's componentconfig (config file) API and the Kubelet's...

- Updated `kubeadm` to use the `InitialCorruptCheck=true` etcd feature gate instead of the deprecated `--experimental-initial-corrupt-check` flag. Also replaced the use of `--experimental-watch-progress-notify-interval` with its graduated counterpart `--watch-progress-notify-interval`. ([#132838](https://github.com/kubernetes/kubernetes/pull/132838), [@AwesomePatrol](https://github.com/AwesomePatrol))

### SIG-cloud-provider

This is the first Kubernetes release for this SIG! In v1.12, SIG Cloud Provider focused on building the processes and infrastructure to better support existing and new cloud providers. Some of these initiatives (many of which are still in progress) are:

- Reporting E2E conformance test results to TestGrid from every cloud provider (in collaboration with SIG Testing & SIG Release)

Node-local DNS cache feature is available in Alpha. This feature deploys a lightweight DNS caching Daemonset that avoids the conntrack and converts queries from UDP to more reliable TCP.
PodReady++ feature now has `kubectl` CLI support.

Progress was made towards finalizing the IPv6 dual stack support KEP and support for topological routing of services.

### SIG Node

* In GCE with COS, increase TasksMax for Docker service to raise cap on number of threads/processes used by containers. ([#51986](https://github.com/kubernetes/kubernetes/pull/51986), [@yujuhong](https://github.com/yujuhong))

* kubeadm alpha certs command now skip missing files ([#85092](https://github.com/kubernetes/kubernetes/pull/85092), [@fabriziopandini](https://github.com/fabriziopandini))

- ` JobTrackingWithFinalizers` enabled by default. This feature allows to keep track of the Job progress without relying on Pods staying in the apiserver.
   ([#110948](https://github.com/kubernetes/kubernetes/pull/110948), [@alculquicondor](https://github.com/alculquicondor))
- `CSIMigrationAWS` upgraded to GA and locked to true.

- Supported fine-grained supplemental groups policy (KEP-3619), which enabled
  fine-grained control for supplementary groups in the first container processes.
  This allows you to choose whether to include groups defined in the container image (/etc/groups)

a pod only applied to CPU resources (such as `cpu_shares`). The Kubernetes cgroup manager uses `memory.limit_in_bytes` in v1 cgroups to limit the memory capacity for a container, and uses `oom_scores` to recommend an order for killing container processes if an out-of-memory event occurs. This implementation has shortcomings: for `Guaranteed` pods, memory can not be fully reserved, and the page cache is at risk of being recycled. For `Burstable` pods, overcommitting memory (setting `request` less...