CoreDNS feature documentation (#6463)

* Initial placeholder PR for CoreDNS feature documentation

* Remove from admin, add content

* Fix missing endcapture

* Add to tasks.yml

* Review feedback

_data/tasks.yml

@@ -143,6 +143,7 @@ toc:
   - docs/tasks/administer-cluster/namespaces.md
   - docs/tasks/administer-cluster/namespaces-walkthrough.md
   - docs/tasks/administer-cluster/dns-horizontal-autoscaling.md
+  - docs/tasks/administer-cluster/coredns.md
   - docs/tasks/administer-cluster/safely-drain-node.md
   - docs/tasks/administer-cluster/cpu-memory-limit.md
   - docs/tasks/administer-cluster/out-of-resource.md

docs/tasks/administer-cluster/coredns.md

@@ -0,0 +1,42 @@
+---
+approvers:
+- johnbelamaric
+title: Using CoreDNS for Service Discovery
+min-kubernetes-server-version: v1.9
+---
+
+{% include feature-state-alpha.md %}
+
+{% capture overview %}
+This page describes how to enable CoreDNS instead of kube-dns for service
+discovery.
+{% endcapture %}
+
+{% capture prerequisites %}
+{% include task-tutorial-prereqs.md %}
+{% endcapture %}
+
+{% capture steps %}
+
+## Installing CoreDNS with kubeadm
+
+In Kubernetes 1.9, [CoreDNS](https://coredns.io) is available as an alpha feature and
+may be installed by setting the `CoreDNS` feature gate to `true` during `kubeadm init`:
+
+```
+kubeadm init --feature-gates=CoreDNS=true
+```
+
+This installs CoreDNS instead of kube-dns.
+
+{% endcapture %}
+
+{% capture whatsnext %}
+
+You can configure [CoreDNS](https://coredns.io) to support many more use cases than
+kube-dns by modifying the `Corefile`. For more information, see the
+[CoreDNS site]https://coredns.io/2017/05/08/custom-dns-entries-for-kubernetes/).
+
+{% endcapture %}
+
+{% include templates/task.md %}