Read the article to know more about the DNS control in Kubernetes with External DNS and Linode. Bobcares, as a part of our Kubernetes Support Service offers solutions to every query that comes our way.

Overview

1. Kubernetes DNS Management with ExternalDNS and Linode
2. How ExternalDNS Works?
3. Workflow Overview
4. Setting Up ExternalDNS with Linode
5. Benefits of Using ExternalDNS
6. Limitations
7. Conclusion

Kubernetes DNS Management with External DNS and Linode

Managing DNS records for Kubernetes applications can be a challenge, especially as services and workloads scale. ExternalDNS, an open-source tool, simplifies this process by dynamically automating DNS record management based on Kubernetes cluster states. It seamlessly integrates with DNS providers like Linode, ensuring the DNS entries are always in sync with the Kubernetes services and ingresses.

Let’s explore how ExternalDNS works, its benefits, and the steps to set it up with Linode.

ExternalDNS bridges the gap between Kubernetes and DNS providers, automating the creation, updating, and deletion of DNS records for Kubernetes resources. Key Features include;

• Automated DNS Management: Automatically manages DNS entries for services and ingresses.

• Multi-Provider Support: Works with DNS providers like Linode, AWS Route 53, and Google Cloud DNS.

• Kubernetes Integration: Leverages annotations in Kubernetes to define DNS behavior.

How ExternalDNS Works?

ExternalDNS monitors the Kubernetes API for changes in resources (e.g., services and ingresses). Based on these changes:

• It creates or updates DNS records via the DNS provider’s API.

• It deletes stale records when resources are removed.

Workflow Overview

• Deployment: Install ExternalDNS as a pod in the Kubernetes cluster.

• Monitoring: It tracks resource changes like service updates.

• DNS Updates: Communicates with the DNS provider (e.g., Linode) to adjust DNS records.

• Cleanup: Removes records when resources are deleted to avoid conflicts.

Setting Up ExternalDNS with Linode

Prerequisites

• Kubernetes Cluster: A functioning Kubernetes setup.

• Linode Account: With a domain configured to use Linode’s DNS servers.

• API Token: Generate a Linode API token with DNS management permissions.

1. Configure Linode Credentials

Log in to Linode Cloud Manager.

Navigate to API Tokens and generate a new token with DNS permissions.

Use this token in your ExternalDNS deployment configuration.

2. Deployment Configuration

Create a Kubernetes deployment manifest for ExternalDNS:

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: registry.k8s.io/external-dns/external-dns:v0.15.0
args:
- --source=service
- --domain-filter=example.com # Replace with your domain
- --provider=linode
env:
- name: LINODE_TOKEN
value: "YOUR_LINODE_API_KEY"

3. Configure RBAC (Role-Based Access Control)

If RBAC is enabled, define a ServiceAccount and ClusterRole:

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"]

4. Deploy and Annotate Resources

Deploy ExternalDNS:

kubectl apply -f externaldns.yaml

Annotate Services:

To create a DNS record for a service, add an annotation:

kubectl annotate service external-dns.alpha.kubernetes.io/hostname=

5. Verify DNS Records

After deployment, verify the records in the Linode Cloud Manager under the DNS section. Ensure the A records match your Kubernetes services’ external IPs.

Benefits of Using ExternalDNS

Automation: Eliminates manual DNS updates, saving time and effort.

Consistency: Ensures DNS records are always up to date with cluster changes.

Flexibility: Works with various DNS providers and Kubernetes resources.

Limitations

Setup Complexity: Requires initial configuration and deployment effort.

Provider Dependency: Relies on the DNS provider’s API, which may affect functionality during outages.

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Conclusion

ExternalDNS is a powerful tool for Kubernetes users who want seamless DNS record management. By integrating with providers like Linode, it streamlines operations, reduces manual overhead, and ensures your DNS records reflect the current state of your cluster.