Cert-Manager introduces Certificates and Issuers as Custom Resource in the Kubernetes Cluster. This simplifies the process of renewing, obtaining and managing those certificates. ACME stands for Automatic Certificate Management Environment. Let’s Encrypt is an ACME Server, which provides free SSL certificate. But before issuing certificates, it verifies if the domain. This verification is done with the help of orders and challenges. Cert Manager creates Custom Resources of Orders and Challenges for the purpose of acquiring ACME Certificates.
- Kubernetes Cluster
- Helm CLI installed
- Owned Domain
- Public facing Load Balancer
To install cert-manager, execute the commands:
helm repo add jetstack https://charts.jetstack.io helm install cert-manager jetstack/cert-manager \ --namespace cert-manager \ --create-namespace \ --set installCRDs=true
This will install the cert-manager. Then to check, the CRDs cert-manager creates:
kubectl get crds | grep cert-manager.io
This will give the list of the CRDs, that cert-manager will create.
Deploy a ingress and map the IP to domain
To deploy nginx ingress, execute the comamnd:
helm upgrade --install ingress-nginx ingress-nginx \ --repo https://kubernetes.github.io/ingress-nginx \ --namespace ingress-nginx --create-namespace
Then, we can check the IP of the Load Balancer Service created using:
kubectl get svc -n ingress-nginx
Then, map the IP to your domain on the DNS server you are using.
Creating a ACME Issuer
Now, we will be using the Issuer and Cluster Issuer resource to create a Certificate Issuer. Cluster Issuer is cluster-scoped while Issuer is namespace-scoped. To create
Let's Encrypt Cluster Issuer, create a
apiVersion: cert-manager.io/v1 kind: ClusterIssuer metadata: name: lets-encrypt spec: acme: email: <email> privateKeySecretRef: name: lets-encrypt-secret # Secret where issuer private key will be stored server: https://acme-v02.api.letsencrypt.org/directory #ACME Server solvers: - http01: ingress: class: nginx
Change nginx to the ingress class of the ingress you are using and run the command
kubectl apply -f issuer.yaml
Now, to check the status of the issuer, execute:
kubectl get clusterissuers
The cluster issuer should show true under ready field. If not give it a bit of time.
Creating a ACME certificate
Now, to create a certificate, create a file
cert.yaml with the content:
apiVersion: cert-manager.io/v1 kind: Certificate metadata: name: tls-cert spec: isCA: false commonName: "<Domain name>" secretName: tls-cert dnsNames: - "<Domain name>" duration: 10000h renewBefore: 30h issuerRef: name: lets-encrypt kind: ClusterIssuer
Now, apply the above yaml using the command:
kubectl apply -f cert.yaml
To check if the certificate is ready, execute:
kubectl get certs
Now, if the certificate state is ready, we can check the namespace where we deployed the certificate. We will see a secret of type tls. We can now use this secret with our ingresses. Behind the scenes, the certificate created an ingress, certificate signing request, orders and challenges. When these were fulfilled, certificate was issued.
In this blog, we have looked how to use Cert manager. And we have learned about certificate management using cert-manager. Now, we can use cert-manager to issue free SSL certificates.