Kubernetes Level 02 Day 06: Deploy Jenkins on Kubernetes

This document outlines the solution for Kubernetes Level 02 Day 06. The objective was to deploy a Jenkins Continuous Integration (CI) server onto a Kubernetes cluster, ensuring it is properly isolated within its own namespace and exposed to users via a NodePort service.

Table of Contents

1. Task Overview
2. Step-by-Step Solution
   • 1. Create Namespace
   • 2. Define the Manifests
   • 3. Apply the Configuration
   • 4. Verification and Access
3. Deep Dive: Jenkins on Kubernetes

---

Task Overview

Objective: Provision a Jenkins CI server accessible via the browser.

• Namespace: jenkins
• Service:
  • Name: jenkins-service
  • Type: NodePort
  • NodePort: 30008
• Deployment:
  • Name: jenkins-deployment
  • Replicas: 1
  • Labels: app: jenkins
  • Container Name: jenkins-container
  • Image: jenkins/jenkins
  • Container Port: 8080

---

Step-by-Step Solution

1. Create Namespace

Start by creating the isolated environment (namespace) where the Jenkins resources will reside.

Command:

kubectl create namespace jenkins

2. Define the Manifests

Create a single YAML file containing both the Deployment and the Service configurations separated by ---.

Command:

vi jenkins-setup.yaml

Content:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: jenkins-deployment
  namespace: jenkins
spec:
  replicas: 1
  selector:
    matchLabels:
      app: jenkins
  template:
    metadata:
      labels:
        app: jenkins
    spec:
      containers:
      - name: jenkins-container
        image: jenkins/jenkins
        ports:
        - containerPort: 8080
---
apiVersion: v1
kind: Service
metadata:
  name: jenkins-service
  namespace: jenkins
spec:
  type: NodePort
  selector:
    app: jenkins
  ports:
    - port: 8080
      targetPort: 8080
      nodePort: 30008

3. Apply the Configuration

Apply the declarative configuration to the cluster.

Command:

kubectl apply -f jenkins-setup.yaml

* Output:

deployment.apps/jenkins-deployment created
service/jenkins-service created

4. Verification and Access

Wait for the Jenkins pod to fully initialize. Jenkins is a heavy Java application, so it may take a minute to reach the Running state and become responsive.

Check Pod Status:

kubectl get pods -n jenkins

Wait until the pod shows 1/1 under the READY column.

Check Service Configuration:

kubectl get svc -n jenkins

Verify that jenkins-service maps port 8080:30008/TCP.

Access the UI: Once the pod is running, open the provided browser or web view feature in your lab environment. Access Jenkins via the Node's IP address on port 30008 (e.g., http://<node-ip>:30008).

(Optional: Retrieve Initial Admin Password) If you are logging in to configure Jenkins, you will need the initial admin password. You can retrieve this by checking the container logs.

kubectl logs deployment/jenkins-deployment -n jenkins

Look for a block of text in the logs that looks like:

Please use the following password to proceed to installation:

8a4b6c3d9e2f4a1b8c7d6e5f4a3b2c1d

This may also be found at: /var/jenkins_home/secrets/initialAdminPassword

---

Deep Dive: Jenkins on Kubernetes

Why run Jenkins in Kubernetes?

Running Jenkins on Kubernetes is incredibly powerful because it allows Jenkins to spin up dynamic "Build Agents" (worker pods) on-demand to run CI/CD pipelines. This ensures that build environments are clean, isolated, and scalable, rather than maintaining static, heavy VM workers.

The Port Configuration

• Container Port (8080): Jenkins natively runs a web server on port 8080 inside the container.
• Target Port (8080): The service routes traffic to port 8080 on the pods.
• Port (8080): The service's internal cluster port.
• NodePort (30008): A high port opened on every single physical node in the Kubernetes cluster. Any traffic hitting a node's IP on port 30008 is forwarded to the Jenkins service.