Improve Kubeadm reference doc (#6103)

* automatically-generated kubeadm reference doc

* user-mantained kubeadm reference doc

docs/reference/setup-tools/kubeadm/kubeadm-reset.md

@@ -0,0 +1,31 @@
+---
+approvers:
+- mikedanese
+- luxas
+- jbeda
+title: kubeadm reset 
+---
+{% capture overview %}
+{% endcapture %}
+
+{% capture body %}
+{% include_relative generated/kubeadm_reset.md %}
+
+### External etcd clean up
+`kubeadm reset` will not delete any etcd data if external etcd is used. This means that if you run `kubeadm init` again using the same etcd endpoints, you will see state from previous clusters. 
+
+To wipe etcd data it is recommended you use a client like etcdctl, such as:
+
+```
+etcdctl del "" --prefix
+```
+
+See [etcd documentation](https://github.com/coreos/etcd/tree/master/etcdctl) for more information.
+{% endcapture %}
+
+{% capture whatsnext %}
+* [kubeadm init](kubeadm-init.md) to bootstrap a Kubernetes master node
+* [kubeadm join](kubeadm-join.md) to bootstrap a Kubernetes worker node and join it to the cluster
+{% endcapture %}
+
+{% include templates/concept.md %}