Welcome to Automating Certificate Management with cert-manager and Let's Encrypt. Manual SSL/TLS certificate rotation is a leading cause of preventable outages. In modern cloud-native environments, certificate lifecycle management must be fully automated.

1. The Rise of Let's Encrypt and ACME

Let's Encrypt revolutionized web security by offering free, automated certificates using the ACME (Automated Certificate Management Environment) protocol. Because these certificates expire every 90 days, manual renewal is impractical. Automation is practically required.

2. Introducing cert-manager for Kubernetes

In a Kubernetes environment, cert-manager is the de facto standard for certificate automation. It runs as a controller within the cluster and extends the Kubernetes API by adding Custom Resource Definitions (CRDs) for Issuers, ClusterIssuers, and Certificates.

When you create a Certificate resource, cert-manager automatically generates a private key and a Certificate Signing Request (CSR). It then communicates with the configured Issuer (e.g., the Let's Encrypt API) to obtain the signed certificate.

3. Solving the ACME Challenge

To prove you own the domain, Let's Encrypt requires you to solve a challenge. cert-manager handles this automatically in two ways:

  • HTTP-01: cert-manager spins up a temporary pod and configures your Ingress controller to route a specific HTTP request (/.well-known/acme-challenge/) to it.
  • DNS-01: cert-manager uses API credentials to create a temporary TXT record in your DNS provider (like Route53 or Cloudflare). This is required for issuing wildcard certificates (e.g., *.example.com).

4. Seamless Integration with Ingress

The true power of cert-manager is its integration with Kubernetes Ingress resources. By simply adding an annotation like cert-manager.io/cluster-issuer: "letsencrypt-prod" to an Ingress YAML file, cert-manager will automatically intercept it, request the certificate for the specified hostnames, and mount it as a Kubernetes Secret. When the certificate is 30 days from expiration, cert-manager quietly renews it in the background.

Conclusion

By implementing cert-manager and the ACME protocol, DevOps teams can completely eliminate the operational overhead and risk of expired certificates, ensuring secure, encrypted traffic for all services by default.