• How to identify the DNS solution used in a cluster: 
    kubectl get pods -n kube-system
  • Usually this is CoreDNS.
  • kube-dns is the name of the service for which to access CoreDNS with.
  • How to check the IP of the CoreDNS server that should be configured on PODS to resolve services?
    • Run kubectl get service -n kube-system and then check the ClusterIP value.
  • Where is the configuration file kept for configuring the CoreDNS service?
    • Check the Args field of the CoreDNS deployment: 
      kubectl -n kube-system describe deployments.apps coredns | grep -A2 Args | grep Corefile
  • In this example, the answer is /etc/coredns/Corefile.
  • How is the Corefile passed into the CoreDNS POD?
    • Check the ConfigMaps, run this command kubectl get cm -n kube-system and check the coredns ConfigMap.
    • It is configured as a ConfigMap object.
  • What is the name of the ConfigMap object created for Corefile?
    • coredns
  • How to check the root domain/zone of the cluster? 
    kubectl describe configmap coredns -n kube-system
  • Example answer is cluster.local
  • What name can be used to access the hr web server from the test application?
    • Run kubectl get svc and get the right service name and port.
      • The example answer is web-service.
  • Anything that has .pod inside of it, cannot be accessed.
  • Troubleshoot why a web server is unable to access a database pod.
    • Run kubectl edit deploy webapp
    • Correct the DB_Host value.
      • In this case it had to be changed from mysql to mysql.payroll.
  • From an HR pod, nslookup the mysql service.
    • Run this command: kubectl exec -it hr -- nslookup mysql.payroll > /root/CKA/nslookup.out

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