DevOps in K8s — CoreDNS, Part Two

DevOps in K8s bootcamp series

Note, full “DevOps in K8s” mind map is available at: “DevOps in K8s Mind Map”

In my article “DevOps in K8s — CoreDNS, Part One”, I introduced the concept of “CoreDNS”, what problem does it solve and how does it work. Let’s see some real world examples.

Busybox Pod Demo

Let’s create a busybox Pod with the following command:

$ kubectl run -it --image busybox:1.25.0 test-pod --restart=Never --rm /bin/sh

/ # cat /etc/resolv.conf
nameserver 10.96.0.10
search default.svc.cluster.local svc.cluster.local cluster.local
options ndots:5
/ #

As you can see from the above output, the /etc/resolv.conf file in busybox pod is pointing to nameserver 10.96.0.10.

This IP address is the CLUSTER-IP of the kube-dns service:

$ kubectl get svc -n kube-system
NAME                      TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)                  AGE
kube-dns                  ClusterIP   10.96.0.10       <none>        53/UDP,53/TCP,9153/TCP   1d

Now let’s query the nginx-service using DNS name:

/ # nsloopup nginx-service.default.svc.cluster.local
Server:    10.96.0.10
Address:   10.96.0.10:53

Name…