External-DNS — Automatic DNS Records for Kubernetes Services

What it is

External-DNS is a Kubernetes controller that watches Services, Ingresses, and other resources and automatically creates, updates, and deletes DNS records in external DNS providers. It supports Route53, Cloudflare, Google Cloud DNS, Azure DNS, and many others. DNS configuration becomes declarative: define your service with an annotation, and External-DNS handles the rest.

This tool is for Kubernetes platform engineers who want DNS to stay in sync with cluster state without manual record management.

How it saves time or tokens

Without External-DNS, deploying a new service to Kubernetes requires manual DNS record creation. External-DNS automates this entirely. When a service is created with the right annotation, DNS records appear. When the service is deleted, records are cleaned up. This eliminates a common source of deployment friction and human error.

How to use

1. Deploy External-DNS to your Kubernetes cluster.
2. Configure it with your DNS provider credentials.
3. Add annotations to your Services or Ingresses.
4. DNS records are created and managed automatically.

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

helm install external-dns external-dns/external-dns \
  --set provider=cloudflare \
  --set cloudflare.apiToken=your-token \
  --set domainFilters[0]=example.com

Example

An annotated Kubernetes Service:

apiVersion: v1
kind: Service
metadata:
  name: my-app
  annotations:
    external-dns.alpha.kubernetes.io/hostname: app.example.com
    external-dns.alpha.kubernetes.io/ttl: '300'
spec:
  type: LoadBalancer
  ports:
    - port: 80
      targetPort: 8080
  selector:
    app: my-app

External-DNS creates an A record for app.example.com pointing to the LoadBalancer IP.

# Ingress example
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: my-app-ingress
  annotations:
    external-dns.alpha.kubernetes.io/hostname: app.example.com
spec:
  rules:
    - host: app.example.com
      http:
        paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: my-app
                port:
                  number: 80

Related on TokRepo

• DevOps tools — Kubernetes and infrastructure tools
• Automation tools — Infrastructure automation

Common pitfalls

• External-DNS needs proper RBAC and DNS provider permissions. Missing permissions cause silent failures without DNS records.
• The --domain-filter flag is important. Without it, External-DNS may try to manage DNS records for domains you do not own.
• DNS propagation takes time. Do not expect records to be resolvable immediately after service creation.
• Multiple External-DNS instances managing the same zone can conflict. Use --txt-owner-id to prevent conflicts.
• Deleting a namespace does not always trigger cleanup. Ensure External-DNS has access to watch deletion events.
• Review the official documentation before deploying to production to ensure compatibility with your specific environment and requirements.
• Start with default settings and customize incrementally. Changing too many configuration options at once makes debugging harder.