Create VMs

Create two VMs - master and worker with below config -

Configure Kubernetes Cluster

Follow steps from below link to install a Kubernetes cluster using kubeadm, comprising just two VMs created in above step -

https://wiki.onap.org/display/DW/Deploying+Kubernetes+Cluster+with+kubeadm

Verify below pods up and running after completing all steps

Note:Instead of kube-dns pod, coredns pod is created.

ubuntu@coredns-1:/dockerdata-nfs$ ls -lrt
total 44
-rw-r--r-- 1 root root  1366 Mar  1 15:00 Corefile
-rw-r--r-- 1 root root   979 Mar  5 14:06 zone.db
ubuntu@coredns-1:/dockerdata-nfs$
root@coredns-1:~# kubectl get pods --all-namespaces
NAMESPACE     NAME                                READY     STATUS    RESTARTS   AGE
kube-system   etcd-kubefed-1                      1/1       Running   0          1h
kube-system   kube-apiserver-kubefed-1            1/1       Running   0          1h
kube-system   kube-controller-manager-kubefed-1   1/1       Running   0          1h
kube-system   coredns-789ff8fd8d-2gxnc            1/1       Running   0          1h
kube-system   kube-proxy-g7bxn                    1/1       Running   0          1h
kube-system   kube-proxy-q82lg                    1/1       Running   0          1h
kube-system   kube-scheduler-kubefed-1            1/1       Running   0          1h
kube-system   tiller-deploy-546cf9696c-fbckp      1/1       Running   0          1h
kube-system   weave-net-9zlrh                     2/2       Running   0          1h
kube-system   weave-net-dn7fj                     2/2       Running   1          1h
root@coredns-1:~#

Modify coredns deployment to configure DNS zone

1. Put attached files - Corefile and zone.db in /dockerdata-nfs using root user.

   ubuntu@coredns-1:/dockerdata-nfs$ ls -lrt
   total 44
   -rw-r--r-- 1 root root  1366 Mar  1 15:00 Corefile
   -rw-r--r-- 1 root root   979 Mar  5 14:06 zone.db
   ubuntu@coredns-1:/dockerdata-nfs$
   
   

2. Edit coredns configmap to reflect the new zone file.

   #Below command opens the codedns configmap for editing. Edit and save the file.
   
   ubuntu@coredns-1:~# kubectl edit configmap coredns -n kube-system
   # Please edit the object below. Lines beginning with a '#' will be ignored,
   # and an empty file will abort the edit. If an error occurs while saving this file will be
   # reopened with the relevant failures.
   #
   apiVersion: v1
   data:
     Corefile: |
       .:53 {
           errors
           log
           health
           kubernetes cluster.local 10.96.0.0/12 {
              pods insecure
           }
           file /dockerdata-nfs/zone.db example.com
           prometheus
           proxy . /etc/resolv.conf
           cache 30
       }
     zone.db: "$ORIGIN example.com.     ; designates the start of this zone file in the
       namespace\n$TTL 1h         ; default expiration time of all resource records without
       their own TTL value\nexample.com.  IN  SOA   ns.example.com. username.example.com.
       ( 2007120710 1d 2h 4w 1h )\nexample.com.  IN  NS    ns                    ; ns.example.com
       is a nameserver for example.com\nexample.com.  IN  NS    ns.somewhere.example.
       ; ns.somewhere.example is a backup nameserver for example.com\nexample.com.  IN
       \ A     10.147.101.135             ; IPv4 address for example.com\nns            IN
       \ A     10.247.5.11             ; IPv4 address for ns.example.com\nwww           IN
       \ CNAME example.com.          ; www.example.com is an alias for example.com\nwwwtest
       \      IN  CNAME www              ; wwwtest.example.com is another alias for www.example.com\nsdnc.example.com.
       \   IN      SRV    30202 10 10 example.com.\nsdnc         IN  A  10.147.99.140"
   kind: ConfigMap
   metadata:
     creationTimestamp: 2018-02-28T20:13:03Z
     name: coredns
     namespace: kube-system
     resourceVersion: "102077"
     selfLink: /api/v1/namespaces/kube-system/configmaps/coredns
     uid: c8489771-1cc3-11e8-a0cb-fa163eabcb60
    
   configmap "coredns" edited
   ubuntu@coredns-1:~#

   Following changes are applied:

   Where	Added Line
   Corefile: | .:53{ ... }	file /dockerdata-nfs/zone.db example.com
   #Before line: kind: ConfigMap #Note that IP addresses in "A record" should point to current active site's master node. example.com. IN A <coredns-vm master ip address> ns IN A <nameserver on fed VM as configured originally in /etc/resolv.conf> sdnc IN A <active site's master IP> //Add active Site IP to direct traffic to.	zone.db: "$ORIGIN example.com. ; designates the start of this zone file in the namespace\n$TTL 1h ; default expiration time of all resource records without their own TTL value\nexample.com. IN SOA ns.example.com. username.example.com. ( 2007120710 1d 2h 4w 1h )\nexample.com. IN NS ns ; ns.example.com is a nameserver for example.com\nexample.com. IN NS ns.somewhere.example. ; ns.somewhere.example is a backup nameserver for example.com\nexample.com. IN \ A 10.147.101.135 ; IPv4 address for example.com\nns IN \ A 10.247.5.11 ; IPv4 address for ns.example.com\nwww IN \ CNAME example.com. ; www.example.com is an alias for example.com\nwwwtest \ IN CNAME www ; wwwtest.example.com is another alias for www.example.com\nsdnc.example.com. \ IN SRV 30202 10 10 example.com.\nsdnc IN A 10.147.99.140"

   The files in step 1 should contain the same entries of coredns configmap, described in step 2. If the files in step 1, are pointing traffic to site IP1 (for example), the coredns configmap in step 2, should also configure site IP1.

3. Edit coredns deployment to specify mount volumes and zone key for coredns.

   ubuntu@coredns-1:~# kubectl -n kube-system edit deployment coredns
   deployment "coredns" edited
   ubuntu@coredns-1:~#

   Make the following changes
   Purpose	Changes
   mount point for new zone file mount point for new coredns config file define new zone key in volumes	Field Added/Replaced Value .spec.template.spec.containers.volumeMounts .spec.template.spec.containers.args Replaced Values: - mountPath: /dockerdata-nfs name: config-volume - conf - /dockerdata-nfs/Corefile  .spec.template.spec.volumes.items Added Values: - key: zone.db path: zone.db

   Deployment config will look as in file coredns-edit-deploymnt.yaml after making athe bove changes.
   Note that editing the deployment will create a new coredns pod and terminate the old one. Verify the new pod is up and running after editing deployment.

   ubuntu@coredns-1:/root$ kubectl get pods --all-namespaces | grep coredns
   kube-system         coredns-789ff8fd8d-2gxnc                        1/1       Running   0          5d
   ubuntu@coredns-1:/root$

4. Edit /etc/resolv.conf to point nameserver to configured coreDNS server.

   ubuntu@coredns-1:~# kubectl get svc --all-namespaces | grep kube-dns
   kube-system         kube-dns               ClusterIP   10.96.0.10       <none>        53/UDP,53/TCP   5d
    
   #Use the above cluster IP to configure in /etc/resolv.conf as shown below
   ubuntu@coredns-1:/root$ sudo vi /etc/resolv.conf
   # Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
   #     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
   nameserver 10.96.0.10
   #nameserver 10.247.5.11
   search openstacklocal
   ubuntu@coredns-1:
    

5.  Lookup the configured domain to verify it is pointing to site as configured above.

   ubuntu@coredns-1:/dockerdata-nfs$ nslookup sdnc.example.com
   Server:         10.96.0.10
   Address:        10.96.0.10#53
   Name:   sdnc.example.com
   Address: 10.147.101.23
    
   #verify it is resolving sites like google.ca backwardly
   ubuntu@coredns-1:/dockerdata-nfs$ nslookup google.ca
   Server:         10.96.0.10
   Address:        10.96.0.10#53
   Non-authoritative answer:
   Name:   google.ca
   Address: 172.217.23.131