cert-manager

cert-manager is an extension for Kubernetes that automates the issuance and renewal of certificates. It allows you to obtain certificates from Let's Encrypt and other certificate authorities (CAs) or use internal root certificates. cert-manager simplifies certificate management by automatically renewing them before expiration and ensuring secure encryption for services within the cluster. It integrates with Ingress controllers and supports various domain verification methods, making it a convenient tool for automating certificate management in Kubernetes.

Installation

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To install cert-manager:

1. Go to the Kubernetes section and click on the cluster.
2. Navigate to the Addons section and select cert-manager.
3. Click Install and wait for the process to complete.

To verify the installation, run the following command:

kubectl get pods -n cert-manager

All pods in the cert-manager namespace should have the status Running.

Usage

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To enable cert-manager to issue certificates, you need to create a ClusterIssuer object, which manages certificates at the cluster level.

Example manifest:

apiVersion: cert-manager.io/v1
kind: ClusterIssuer
metadata:
  name: letsencrypt-prod
spec:
  acme:
    email: email@example.com
    server: https://acme-v02.api.letsencrypt.org/directory
    privateKeySecretRef:
      name: letsencrypt-prod
    solvers:
    - http01:
        ingress:
          class: nginx

Here:

• email – Your email address, required for certificate issuance. Let's Encrypt will send notifications to this address.
• server – The URL of Let's Encrypt or another certificate authority.
• privateKeySecretRef – The secret that stores the private key.
• solvers.http01.ingress.class – The method for verifying domain ownership via HTTP, using the Nginx Ingress controller in this case.

If you're using a different Ingress controller, replace nginx with the appropriate value. For example, for Traefik:

solvers:
  - http01:
      ingress:
        class: traefik

Example Usage of cert-manager

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Let's consider an example where cert-manager is used with resources from our Nginx Ingress setup.

If you followed our guide, you have already set up:

• Three deployments
• Nginx Ingress
• A LoadBalancer

Your services are accessible via:

• http://ingress1.example.com/service1
• http://ingress1.example.com/service2
• http://ingress2.example.com/

Now we need to define a ClusterIssuer in a file named cluster-issuer.yaml:

apiVersion: cert-manager.io/v1
kind: ClusterIssuer
metadata:
  name: letsencrypt-prod
spec:
  acme:
    email: email@example.com
    server: https://acme-v02.api.letsencrypt.org/directory
    privateKeySecretRef:
      name: letsencrypt-prod
    solvers:
    - http01:
        ingress:
          class: nginx

Apply the manifest:

kubectl apply -f cluster-issuer.yaml

Next, you need to update the Ingress resource. Modify the existing Ingress manifest by adding an annotation for cert-manager and a tls section.

Updated ingress.yaml:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: example-ingress
  namespace: ingress-example
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /
    cert-manager.io/cluster-issuer: letsencrypt-prod
spec:
  rules:
  - host: ingress1.example.com
    http:
      paths:
      - path: /service1
        pathType: Prefix
        backend:
          service:
            name: service1
            port:
              number: 80
      - path: /service2
        pathType: Prefix
        backend:
          service:
            name: service2
            port:
              number: 80
  tls:
  - hosts:
    - ingress1.example.com
    secretName: ingress-tls

Changes in this manifest:

1. Added the annotation cert-manager.io/cluster-issuer: letsencrypt-prod to instruct cert-manager to use the created ClusterIssuer.

2. Added the tls section, specifying the domains for which cert-manager should issue certificates and the secret (ingress-tls) where they will be stored.

Apply the updated manifest:

kubectl apply -f ingress.yaml

After a short period, cert-manager will issue the certificates and store them in the ingress-tls secret. To check the certificates, use:

kubectl get secret ingress-tls -n ingress-example -o yaml

If successful, the secret should contain tls.crt and tls.key.

Run the following command to test HTTPS connectivity:

curl -v https://ingress1.example.com/service1

If the request completes without errors, the certificates are successfully installed, and the services are running over HTTPS.