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Setting up ExternalDNS for Dyn

Creating a Dyn Configuration Secret

For ExternalDNS to access the Dyn API, create a Kubernetes secret.

To create the secret:

$ kubectl create secret generic external-dns \
      --from-literal=EXTERNAL_DNS_DYN_CUSTOMER_NAME=${DYN_CUSTOMER_NAME} \
      --from-literal=EXTERNAL_DNS_DYN_USERNAME=${DYN_USERNAME} \
      --from-literal=EXTERNAL_DNS_DYN_PASSWORD=${DYN_PASSWORD}

The credentials are the same ones created during account registration. As best practise, you are advised to create an API-only user that is entitled to only the zones intended to be changed by ExternalDNS

Deploy ExternalDNS

The rest of this tutorial assumes you own example.com domain and your DNS provider is Dyn. Change example.com with a domain/zone that you really own.

In case of the dyn provider, the flag --zone-id-filter is mandatory as it specifies which zones to scan for records. Without it

Create a deployment file called externaldns.yaml with the following contents:

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:
      containers:
      - name: external-dns
        image: k8s.gcr.io/external-dns/external-dns:v0.7.6
        args:
        - --source=ingress
        - --txt-prefix=_d
        - --namespace=example
        - --zone-id-filter=example.com
        - --domain-filter=example.com
        - --provider=dyn
        env:
        - name: EXTERNAL_DNS_DYN_CUSTOMER_NAME
          valueFrom:
            secretKeyRef:
              name: external-dns
              key: EXTERNAL_DNS_DYN_CUSTOMER_NAME
        - name: EXTERNAL_DNS_DYN_USERNAME
          valueFrom:
            secretKeyRef:
              name: external-dns
              key: EXTERNAL_DNS_DYN_USERNAME
        - name: EXTERNAL_DNS_DYN_PASSWORD
          valueFrom:
            secretKeyRef:
              name: external-dns
              key: EXTERNAL_DNS_DYN_PASSWORD
EOF

As we'll be creating an Ingress resource, you need --txt-prefix=_d as a CNAME cannot coexist with a TXT record. You can change the prefix to any valid start of a FQDN.

Create the deployment for ExternalDNS:

$ kubectl create -f externaldns.yaml

Running a locally build version

If you just want to test ExternalDNS in dry-run mode locally without doing the above deployment you can also do it. Make sure your kubectl is configured correctly . Assuming you have the sources, build and run it like so:

make 
# output skipped

./build/external-dns \
    --provider=dyn \
    --dyn-customer-name=${DYN_CUSTOMER_NAME} \
    --dyn-username=${DYN_USERNAME} \
    --dyn-password=${DYN_PASSWORD} \
    --domain-filter=example.com \
    --zone-id-filter=example.com \
    --namespace=example \
    --log-level=debug \
    --txt-prefix=_ \
    --dry-run=true
INFO[0000] running in dry-run mode. No changes to DNS records will be made. 
INFO[0000] Connected to cluster at https://some-k8s-cluster.example.com 
INFO[0001] Zones: [example.com]
# output skipped

Having --dry-run=true and --log-level=debug is a great way to see exactly what DynamicDNS is doing or is about to do.

Deploying an Ingress Resource

Create a file called 'test-ingress.yaml' with the following contents:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:  
  name: test-ingress
  namespace: example
spec:
  rules:
  - host: test-ingress.example.com
    http:
      paths:
      - backend:
          service:
            name: my-awesome-service
            port:
              number: 8080
        pathType: Prefix

As the DNS name test-ingress.example.com matches the filter, external-dns will create two records: a CNAME for test-ingress.example.com and TXT for _dtest-ingress.example.com.

Create the Ingress:

$ kubectl create -f test-ingress.yaml

By default external-dns scans for changes every minute so give it some time to catch up with the

Verifying Dyn DNS records

Login to the console at https://portal.dynect.net/login/ and verify records are created

Clean up

Login to the console at https://portal.dynect.net/login/ and delete the records created. Alternatively, just delete the sample Ingress resources and external-dns will delete the records.