We have set up several components to see how DNS entries are created initially. The Kubernetes Service name is especially important for determining the name of a DNS.

However, Kubernetes Service has 2 modes, either normal service or headless service. Normal service has already been described in the preceding section; it has its own IP address. On the other hand, headless service doesn't have an IP address.

$ kubectl expose deploy my-apache --namespace=chap8-domain1 --name=my-apache-svc-hl --port=80 --type=ClusterIP --cluster-ip=None
service "my-apache-svc-hl" exposed

$ kubectl expose deploy my-apache --namespace=chap8-domain2 --name=my-apache-svc-hl --port=80 --type=ClusterIP --cluster-ip=None
service "my-apache-svc-hl" exposed

2. Check there is no IP address for those two headless services with the following command:

$ kubectl get svc my-apache-svc-hl --namespace=chap8-domain1
NAME               TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)   AGE
my-apache-svc-hl   ClusterIP   None         <none>        80/TCP    13m


$ kubectl get svc my-apache-svc-hl --namespace=chap8-domain2
NAME               TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)   AGE
my-apache-svc-hl   ClusterIP   None         <none>        80/TCP    13m

3. Launch the busybox pod in the foreground:

$ kubectl run -it busybox --restart=Never --image=busybox

4. In the busybox pod, query those two services. It must show the addresses as the pod's address (172.168.0.4 and 172.168.0.5):

# nslookup my-apache-svc-hl.chap8-domain1.svc.cluster.local
Server: 10.96.0.10
Address 1: 10.96.0.10 kube-dns.kube-system.svc.cluster.local

Name: my-apache-svc-hl.chap8-domain1.svc.cluster.local
Address 1: 172.17.0.4


# nslookup my-apache-svc-hl.chap8-domain2.svc.cluster.local
Server: 10.96.0.10
Address 1: 10.96.0.10 kube-dns.kube-system.svc.cluster.local

Name: my-apache-svc-hl.chap8-domain2.svc.cluster.local
Address 1: 172.17.0.5

5. Exit the busybox pod and delete it:

# exit
$ kubectl delete pod busybox
pod "busybox" deleted