Install Jenkins on Kubernetes

CI/CD (Continuous Integration/ Continuous Deployment) is a core concept of the DevOps world. It helps us to automate the software development processes: building, testing and deploying the source codes.

Among many CI/CD tools, Jenkins is one of the most well-known open-source tool that help setting up the pipelines for continuous integration and continuous deployment.

This tutorial will show you the way to install Jenkins on a Kubernetes cluster.

Preparing a Kubernetes cluster

There are many ways to setup a Kubernetes cluster. You can use the public cloud services to provision your own cluster on AWS, GCP, Linode, etc. Besides, the simplest way is installing minikube on your local machine.

Here, I have a Kubernetes cluster with 5 nodes provisioned by using kubespray.

$ kubectl get node

Kubernetes cluster

Installing Jenkins

Firstly, we will create a new namespace to provide the isolation mechanism for controlling the CI environment:

$ kubectl create namespace jenkins
namespace/jenkins created

Verifying that the namespace jenkins was successfully created by running the following command:

$ kubectl get namespaces

Namespace jenkins

Then, let’s create Jenkins deployment. You can use the following manifest file to create a single instance deployment of Jenkins.

Creating file `jenkins-deployment.yaml`:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: jenkins-deployment
spec:
  replicas: 1
  selector:
    matchLabels:
      app: jenkins
  template:
    metadata:
      labels:
        app: jenkins
    spec:
      containers:
      - name: jenkins
        image: jenkins/jenkins:lts
        ports:
          - name: http-port
            containerPort: 8080
          - name: jnlp-port
            containerPort: 50000
        volumeMounts:
          - name: jenkins-vol
            mountPath: /var/jenkins_vol
      volumes:
        - name: jenkins-vol
          emptyDir: {}

The deployment using the Docker image `jenkins/jenkins:lts` and expose ports `8080` and `50000`.

Apply the above manifest:

$ kubectl create -f jenkins-deployment.yaml --namespace jenkins

It takes a few minutes to pull the image jenkins/jenkins:lts and make the pod running. Verifying that the Jenkins deployment was successfully deployed:

$ kubectl get pod -n jenkins                                                                                                                                                      

NAME                                  READY     STATUS   RESTARTS   AGE
jenkins-deployment-794699f9bc-rln7x   1/1 	Running  0      	  66s

Deploying Jenkins service

After creating the Jenkins deployment and the Jenkins pod is running, you have to expose the connection to the running pod using a service. In this tutorial, we will use NodePort and ClusterIP services.

Let’s create file `jenkins-svc.yaml` as follows:

apiVersion: v1
kind: Service
metadata:
  name: jenkins
spec:
  type: NodePort
  ports:
    - port: 8080
      targetPort: 8080
      nodePort: 30000
  selector:
    app: jenkins

---
apiVersion: v1
kind: Service
metadata:
  name: jenkins-jnlp
spec:
  type: ClusterIP
  ports:
    - port: 50000
      targetPort: 50000
  selector:
    app: jenkins

Now, apply the above manifest and create the service in namespace `jenkins`:

$ kubectl create -f jenkins-svc.yaml --namespace jenkins

Verify that the service is running:

$ kubectl get svc --namespace jenkins                                                                                                                                                   	
NAME       	  TYPE    	CLUSTER-IP 	 EXTERNAL-IP   PORT(S)      	  AGE
jenkins    	  NodePort	10.233.2.81	     	   8080:30000/TCP   30s
jenkins-jnlp  ClusterIP 10.233.53.44     	   50000/TCP    	  30s

From now on, we can access the Jenkins dashboard using the NodePort service.

Accessing the Jenkins dashboard

The NodePort service is accessible from port `30000` on any worker node of the Kubernetes cluster:

`http://worker_node_ip_address:30000`

You can get the IP address of worker nodes by the following command:

$ kubectl get node -o wide

NAME	STATUS   ROLES	AGE	VERSION   INTERNAL-IP 	EXTERNAL-IP   OS-IMAGE         	KERNEL-VERSION   	CONTAINER-RUNTIME
node1   Ready	master   149m   v1.19.2   192.168.0.111       	Ubuntu 18.04.5 LTS   4.15.0-121-generic   docker://19.3.13
node2   Ready	master   148m   v1.19.2   192.168.0.112       	Ubuntu 18.04.5 LTS   4.15.0-121-generic   docker://19.3.13
node3   Ready	master   148m   v1.19.2   192.168.0.113       	Ubuntu 18.04.5 LTS   4.15.0-121-generic   docker://19.3.13
node4   Ready	   147m   v1.19.2   192.168.0.114       	Ubuntu 18.04.5 LTS   4.15.0-121-generic   docker://19.3.13
node5   Ready	   147m   v1.19.2   192.168.0.115       	Ubuntu 18.04.5 LTS   4.15.0-121-generic   docker://19.3.13

For example, let’s open the web browser and go to: `http://192.168.0.111:30000`

Jenkins setup administrator password

In order to retrieve the Administrator password, you can run the following command:

$ kubectl logs jenkins-deployment-794699f9bc-rln7x --namespace jenkins

Get jenkins administrator password

Enter the Administrator password then follow the next setup steps and you will successfully access to the Jenkins dashboard.

Jenkins welcome page

Conclusion

Jenkins is a really powerful CI/CD tool for any DevOps engineer and also software developer. This tutorial has gone through all steps of deploying Jenkins on a Kubernetes cluster. Thanks to Jenkins, we will be more productive and it helps us reduce time to build, test and deploy codes.

Thanks for reading and please leave your suggestion in the below comment section.