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11-dns-addon.md

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DNS in a Kubernetes Pod Network

  • Provides a DNS service to be used by pods within the network.
  • Configures containers to use the DNS service to perform DNS lookups for example
    • You can access services using DNS names assigned to them.
    • You can access other pods using DNS names

Deploying the DNS Cluster Add-on

In this lab you will deploy the DNS add-on which provides DNS based service discovery, backed by CoreDNS, to applications running inside the Kubernetes cluster.

Deploying the DNS Cluster Add-on In this lab you will deploy the DNS add-on which provides DNS based service discovery, backed by CoreDNS, to applications running inside the Kubernetes cluster. The DNS Cluster Add-on

The DNS Cluster Add-on

Deploy the coredns cluster add-on:

kubectl apply -f https://storage.googleapis.com/kubernetes-the-hard-way/coredns-1.8.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.apps/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

it take 3 min then the pods will up

output

coredns-8494f9c688-j97h2   1/1     Running   5          3m31s
coredns-8494f9c688-wjn4n   1/1     Running   1          3m31s

Verification

Create a busybox deployment:

kubectl run 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   1/1     Running   0          3s

Retrieve the full name of the busybox pod:

POD_NAME=$(kubectl get pods -l run=busybox -o jsonpath="{.items[0].metadata.name}")

Execute a DNS lookup for the kubernetes service inside the busybox pod:

kubectl exec -ti $POD_NAME -- nslookup kubernetes

output

Server:    10.32.0.10
Address 1: 10.32.0.10 kube-dns.kube-system.svc.cluster.local

Name:      kubernetes
Address 1: 10.32.0.1 kubernetes.default.svc.cluster.local

Next: Smoke Test