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12.DNS-Add-On.md

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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.

Enable resolved

for instance in worker-01 worker-02 worker-03
do 
 ssh -t k8s@${instance} sudo systemctl enable systemd-resolved.service
 ssh -t k8s@${instance} sudo systemctl start  systemd-resolved.service
done

The DNS Cluster Add-on

Deploy the coredns cluster add-on:

kubectl apply -f https://raw.githubusercontent.com/ansilh/kubernetes-the-hardway-virtualbox/master/config/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-699f8ddd77-5bszs   1/1     Running   0          11m
coredns-699f8ddd77-bz2jd   1/1     Running   0          11m

Verification

Create a run-once dnstool Pod:

kubectl run -it --rm --restart=Never --image=infoblox/dnstools:latest dnstools
  • From temonal execute nslookup
dnstools# time nslookup kubernetes
Server:         172.168.0.2
Address:        172.168.0.2#53

Name:   kubernetes.default.svc.cluster.local
Address: 172.168.0.1

real    0m 0.00s
user    0m 0.00s
sys     0m 0.00s
  • Exit from terminal (Pod will be removed automatically after exit.!)

Part 13 - Bare Metal Load Balancer Configuration