gitops/dns

Private DNS installation

Contexte

We want to deploy an internal DNS to serve private domain and that will be able to forward any other requests to another DNS.

Architecture

We will use CoreDNS (not the cluster internal) to serve those requests. A etcd cluster will be deployed in statefullset, with PVC, as CoreDNS' backend. We finally deploy external-dns to handle DNS entry creation and suppression, in Service or Ingress rules.

Deploy

Pretty straitforward using manifests from 01* to 04*.

The CoreDNS configuration is in 04-coredns.yaml :

data:
  Corefile: |
    open-it.intra {
        errors
        health
        log
        etcd {
           endpoint http://etcd-dns:2379
        }
        cache 30
        prometheus 0.0.0.0:9153
    }
    
    . {
        forward . 192.168.5.1
        cache
    }

Testing

We will test by deploying a service type LoadBalancer with the annotation : external-dns.alpha.kubernetes.io/hostname: "<url|fqdn>"

Let's try with that Service :

    apiVersion: v1
    kind: Service
    metadata:
      name: nginx-frontend
      annotations:
        external-dns.alpha.kubernetes.io/hostname: "nginx.open-it.intra"
    spec:
      ports:
      - name: "web"
        port: 80
        targetPort: 80
      selector:
        app: nginx
      type: LoadBalancer

First, let's retrieve DNS IP :

$ kubectl -n dns get svc coredns
NAME      TYPE           CLUSTER-IP     EXTERNAL-IP     PORT(S)        AGE
coredns   LoadBalancer   10.98.74.182   192.168.5.201   53:30690/UDP   2d1h

We can now try DNS resolution

$ dig @192.168.5.201 nginx.open-it.intra +short
192.168.5.203

or

$ nslookup nginx.open-it.intra 192.168.5.201
Server:         192.168.5.201
Address:        192.168.5.201#53

Name:   nginx.open-it.intra
Address: 192.168.5.203

To do

Add a file with static entries.