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Setting up ExternalDNS for PowerDNS

Prerequisites

The provider has been written for and tested against PowerDNS v4.1.x and thus requires PowerDNS Auth Server >= 4.1.x

PowerDNS provider support was added via this PR, thus you need to use external-dns version >= v0.5

The PDNS provider expects that your PowerDNS instance is already setup and
functional. It expects that zones, you wish to add records to, already exist
and are configured correctly. It does not add, remove or configure new zones in
anyway.

Feature Support

The PDNS provider currently does not support:

  • Dry running a configuration is not supported

Deployment

Deploying external DNS for PowerDNS is actually nearly identical to deploying
it for other providers. This is what a sample deployment.yaml looks like:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: external-dns
spec:
  strategy:
    type: Recreate
  selector:
    matchLabels:
      app: external-dns
  template:
    metadata:
      labels:
        app: external-dns
    spec:
      # Only use if you're also using RBAC
      # serviceAccountName: external-dns
      containers:
      - name: external-dns
        image: k8s.gcr.io/external-dns/external-dns:v0.7.6
        args:
        - --source=service # or ingress or both
        - --provider=pdns
        - --pdns-server={{ pdns-api-url }}
        - --pdns-api-key={{ pdns-http-api-key }}
        - --txt-owner-id={{ owner-id-for-this-external-dns }}
        - --domain-filter=external-dns-test.my-org.com # will make ExternalDNS see only the zones matching provided domain; omit to process all available zones in PowerDNS
        - --log-level=debug
        - --interval=30s

Domain Filter (--domain-filter)

When the --domain-filter argument is specified, external-dns will only create DNS records for host names (specified in ingress objects and services with the external-dns annotation) related to zones that match the --domain-filter argument in the external-dns deployment manifest.

eg. --domain-filter=example.org will allow for zone example.org and any zones in PowerDNS that ends in .example.org, including an.example.org, ie. the subdomains of example.org.

eg. --domain-filter=.example.org will allow only zones that end in .example.org, ie. the subdomains of example.org but not the example.org zone itself.

The filter can also match parent zones. For example --domain-filter=a.example.com will allow for zone example.com. If you want to match parent zones, you cannot pre-pend your filter with a “.”, eg. --domain-filter=.example.com will not attempt to match parent zones.

RBAC

If your cluster is RBAC enabled, you also need to setup the following, before you can run external-dns:

apiVersion: v1
kind: ServiceAccount
metadata:
  name: external-dns
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: external-dns
rules:
- apiGroups: [""]
  resources: ["services","endpoints","pods"]
  verbs: ["get","watch","list"]
- apiGroups: ["extensions","networking.k8s.io"]
  resources: ["ingresses"]
  verbs: ["get","watch","list"]
- apiGroups: [""]
  resources: ["pods"]
  verbs: ["get","watch","list"]
- apiGroups: [""]
  resources: ["nodes"]
  verbs: ["list"]
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: external-dns-viewer
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: external-dns
subjects:
- kind: ServiceAccount
  name: external-dns
  namespace: default

Testing and Verification

Important!: Remember to change example.com with your own domain throughout the following text.

Spin up a simple “Hello World” HTTP server with the following spec (kubectl apply -f):

apiVersion: apps/v1
kind: Deployment
metadata:
  name: echo
spec:
  selector:
    matchLabels:
      app: echo
  template:
    metadata:
      labels:
        app: echo
    spec:
      containers:
      - image: hashicorp/http-echo
        name: echo
        ports:
        - containerPort: 5678
        args:
          - -text="Hello World"
---
apiVersion: v1
kind: Service
metadata:
  name: echo
  annotations:
    external-dns.alpha.kubernetes.io/hostname: echo.example.com
spec:
  selector:
    app: echo
  type: LoadBalancer
  ports:
    - protocol: TCP
      port: 80
      targetPort: 5678

Important!: Don’t run dig, nslookup or similar immediately (until you’ve
confirmed the record exists). You’ll get hit by negative DNS caching, which is hard to flush.

Run the following to make sure everything is in order:

$ kubectl get services echo
$ kubectl get endpoints echo

Make sure everything looks correct, i.e the service is defined and receives a
public IP, and that the endpoint also has a pod IP.

Once that’s done, wait about 30s-1m (interval for external-dns to kick in), then do:

$ curl -H "X-API-Key: ${PDNS_API_KEY}" ${PDNS_API_URL}/api/v1/servers/localhost/zones/example.com. | jq '.rrsets[] | select(.name | contains("echo"))'

Once the API shows the record correctly, you can double check your record using:

$ dig @${PDNS_FQDN} echo.example.com.

Last update: June 23, 2021
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