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Deploying kube-dns in a Kubernetes Cluster

Pods can communicate with each other and with services via their IP addresses, once networking has been set up in a Kubernetes cluster. But it is easier to locate other pods and services by hostname, since IP addresses can change. In order to do this, the cluster requires a DNS service. In this learning activity, you will learn how to deploy *kube-dns* to a cluster in order to provide DNS service to pods.

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Path Info

Level

Intermediate

Duration

1h 0m

Published

Sep 28, 2018

Challenge

Deploy kube-dns to the cluster.
You can deploy kube-dns to the cluster like so:
```
kubectl create -f https://raw.githubusercontent.com/ACloudGuru-Resources/kthw-lab-scripts/master/kube-dns.yaml
```
Verify that the kube-dns pod starts up correctly:
```
kubectl get pods -l k8s-app=kube-dns -n kube-system
```
You should get output showing the kube-dns pod. It should look something like this:
```
NAME                        READY     STATUS    RESTARTS   AGE
kube-dns-598d7bf7d4-spbmj   3/3       Running   0          36s
```
Make sure that 3/3 containers are ready and that the pod has a status of Running. It may take a moment for the pod to be fully up and running, so if READY is not 3/3 at first, check again after a few moments.
Challenge

Test the DNS by creating a service, and perform a DNS lookup for service from another pod using the service name
Test the DNS by creating a service, and access the service from another pod using the service name.

Create a simple service like so:
```
kubectl run nginx --image=nginx
```
```
kubectl expose deployment nginx --port 80
```
Get a list of services:
```
kubectl get svc
```
You should see the nginx service listed.

Spin up a busybox pod for testing and get the pod name:
```
kubectl run busybox --image=busybox:1.28 --command -- sleep 3600
```
```
POD_NAME=$(kubectl get pods -l run=busybox -o jsonpath="{.items[0].metadata.name}")
```
Perform a DNS lookup of the nginx service from within the busybox pod to verify that DNS is working:
```
kubectl exec $POD_NAME -- nslookup nginx
```
You should get output that looks like this:
```
Server:    10.32.0.10
Address 1: 10.32.0.10 kube-dns.kube-system.svc.cluster.local

Name:      nginx
Address 1: 10.32.0.248 nginx.default.svc.cluster.local
```

Author

A Cloud Guru

The Cloud Content team comprises subject matter experts hyper focused on services offered by the leading cloud vendors (AWS, GCP, and Azure), as well as cloud-related technologies such as Linux and DevOps. The team is thrilled to share their knowledge to help you build modern tech solutions from the ground up, secure and optimize your environments, and so much more!

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