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docs/14-dns-addon.md

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+# Deploying the DNS Cluster Add-on
+
+In this lab you will deploy the [DNS add-on](https://kubernetes.io/docs/concepts/services-networking/dns-pod-service/) which provides DNS based service discovery, backed by [CoreDNS](https://coredns.io/), to applications running inside the Kubernetes cluster.
+
+## The DNS Cluster Add-on
+
+Deploy the `coredns` cluster add-on:
+
+```
+kubectl apply -f https://raw.githubusercontent.com/mmumshad/kubernetes-the-hard-way/master/deployments/coredns.yaml
+```
+
+> output
+
+```
+serviceaccount/coredns created
+clusterrole.rbac.authorization.k8s.io/system:coredns created
+clusterrolebinding.rbac.authorization.k8s.io/system:coredns created
+configmap/coredns created
+deployment.extensions/coredns created
+service/kube-dns created
+```
+
+List the pods created by the `kube-dns` deployment:
+
+```
+kubectl get pods -l k8s-app=kube-dns -n kube-system
+```
+
+> output
+
+```
+NAME                       READY   STATUS    RESTARTS   AGE
+coredns-699f8ddd77-94qv9   1/1     Running   0          20s
+coredns-699f8ddd77-gtcgb   1/1     Running   0          20s
+```
+
+## Verification
+
+Create a `busybox` deployment:
+
+```
+kubectl run --generator=run-pod/v1  busybox --image=busybox:1.28 --command -- sleep 3600
+```
+
+List the pod created by the `busybox` deployment:
+
+```
+kubectl get pods -l run=busybox
+```
+
+> output
+
+```
+NAME                      READY   STATUS    RESTARTS   AGE
+busybox-bd8fb7cbd-vflm9   1/1     Running   0          10s
+```
+
+Execute a DNS lookup for the `kubernetes` service inside the `busybox` pod:
+
+```
+kubectl exec -ti busybox -- nslookup kubernetes
+```
+
+> output
+
+```
+Server:    10.96.0.10
+Address 1: 10.96.0.10 kube-dns.kube-system.svc.cluster.local
+
+Name:      kubernetes
+Address 1: 10.96.0.1 kubernetes.default.svc.cluster.local
+```
+
+Next: [Smoke Test](15-smoke-test.md)