ExternalDNS

ExternalDNS synchronizes Kubernetes Services and Ingresses with DNS providers, automatically creating and updating DNS records.

Installation with Helm

# Install ExternalDNS via Helm
helm repo add external-dns https://kubernetes-sigs.github.io/external-dns/
helm repo update

helm install external-dns external-dns/external-dns \
  --namespace external-dns \
  --create-namespace \
  --values values.yaml

AWS Route 53 Configuration

# values-aws.yaml — Helm values for AWS Route 53 provider
provider:
  name: aws

env:
  - name: AWS_DEFAULT_REGION
    value: us-east-1

extraArgs:
  - --source=service
  - --source=ingress
  - --domain-filter=example.com
  - --aws-zone-type=public
  - --policy=upsert-only
  - --registry=txt
  - --txt-owner-id=my-cluster

serviceAccount:
  annotations:
    eks.amazonaws.com/role-arn: arn:aws:iam::123456789012:role/external-dns

// iam-policy.json — IAM policy for ExternalDNS Route 53 access
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": ["route53:ChangeResourceRecordSets"],
      "Resource": ["arn:aws:route53:::hostedzone/Z1234567890"]
    },
    {
      "Effect": "Allow",
      "Action": ["route53:ListHostedZones", "route53:ListResourceRecordSets", "route53:ListTagsForResource"],
      "Resource": ["*"]
    }
  ]
}

Google Cloud DNS Configuration

# values-gcp.yaml — Helm values for Google Cloud DNS provider
provider:
  name: google

extraArgs:
  - --source=service
  - --source=ingress
  - --domain-filter=example.com
  - --google-project=my-gcp-project
  - --google-zone-visibility=public
  - --policy=sync
  - --registry=txt
  - --txt-owner-id=my-cluster

Cloudflare Configuration

# values-cloudflare.yaml — Helm values for Cloudflare provider
provider:
  name: cloudflare

env:
  - name: CF_API_TOKEN
    valueFrom:
      secretKeyRef:
        name: cloudflare-api-token
        key: api-token

extraArgs:
  - --source=service
  - --source=ingress
  - --domain-filter=example.com
  - --cloudflare-proxied
  - --policy=sync

# cloudflare-secret.yaml — Cloudflare API token secret
apiVersion: v1
kind: Secret
metadata:
  name: cloudflare-api-token
  namespace: external-dns
type: Opaque
stringData:
  api-token: "your-cloudflare-api-token"

Service Annotations

# service-lb.yaml — LoadBalancer service with DNS annotations
apiVersion: v1
kind: Service
metadata:
  name: web-app
  annotations:
    external-dns.alpha.kubernetes.io/hostname: app.example.com
    external-dns.alpha.kubernetes.io/ttl: "300"
spec:
  type: LoadBalancer
  selector:
    app: web-app
  ports:
    - port: 80
      targetPort: 8080

# service-multi.yaml — Service with multiple DNS hostnames
apiVersion: v1
kind: Service
metadata:
  name: api-service
  annotations:
    external-dns.alpha.kubernetes.io/hostname: "api.example.com,api-v2.example.com"
    external-dns.alpha.kubernetes.io/ttl: "60"
    external-dns.alpha.kubernetes.io/cloudflare-proxied: "true"
spec:
  type: LoadBalancer
  selector:
    app: api
  ports:
    - port: 443
      targetPort: 8443

Ingress Annotations

# ingress-dns.yaml — Ingress with ExternalDNS auto-registration
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: web-app
  annotations:
    external-dns.alpha.kubernetes.io/ttl: "120"
    cert-manager.io/cluster-issuer: letsencrypt-prod
spec:
  ingressClassName: nginx
  tls:
    - hosts:
        - app.example.com
      secretName: app-tls
  rules:
    - host: app.example.com
      http:
        paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: web-app
                port:
                  number: 80

Istio Gateway Source

# values-istio.yaml — ExternalDNS with Istio Gateway source
extraArgs:
  - --source=istio-gateway
  - --source=istio-virtualservice
  - --domain-filter=example.com
  - --policy=sync

Full Deployment Manifest

# external-dns-deploy.yaml — ExternalDNS deployment without Helm
apiVersion: apps/v1
kind: Deployment
metadata:
  name: external-dns
  namespace: external-dns
spec:
  replicas: 1
  selector:
    matchLabels:
      app: external-dns
  template:
    metadata:
      labels:
        app: external-dns
    spec:
      serviceAccountName: external-dns
      containers:
        - name: external-dns
          image: registry.k8s.io/external-dns/external-dns:v0.14.0
          args:
            - --source=service
            - --source=ingress
            - --domain-filter=example.com
            - --provider=aws
            - --policy=sync
            - --registry=txt
            - --txt-owner-id=my-cluster
            - --interval=1m
            - --log-level=info
          env:
            - name: AWS_DEFAULT_REGION
              value: us-east-1

Common Commands

# Check ExternalDNS logs
kubectl logs -n external-dns deploy/external-dns -f

# Verify DNS records were created
dig app.example.com
nslookup app.example.com

# Check TXT ownership records
dig TXT app.example.com

# Dry-run mode (add to args)
# --dry-run  — logs changes without applying