Module 8 - Build Automation & CI/CD with Jenkins

This repository contains a demo project created as part of my DevOps studies in the TechWorld with Nana – DevOps Bootcamp.

https://www.techworld-with-nana.com/devops-bootcamp

Demo Project: Create a CI Pipeline with Jenkinsfile (Freestyle, Pipeline, Multibranch Pipeline)

Technologies used: Jenkins, Docker, Linux, Git, Java, Maven

Project Description:

CI Pipeline for a Java Maven application to build and push to the repository

• Install Build Tools (Maven, Node) in Jenkins
• Make Docker available on Jenkins server
• Create Jenkins credentials for a git repository
• Create different Jenkins job types (Freestyle, Pipeline, Multibranch pipeline) for the Java Maven project with Jenkinsfile to:
  • a. Connect to the application’s git repository
  • b. Build Jar
  • c. Build Docker Image
  • d. Push to private DockerHub repository

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Prerequisites

Before starting, complete all steps to install Jenkins on DigitalOcean:

• jenkins-module-8.1

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Install Build Tools (Maven, Node) in Jenkins

1. Configure Maven plugin

Navigate to Manage Jenkins > Tools > Maven installations

Click Add Maven and fill in:

Field	Value
Name	maven-3.9

Click Save.

2. Install Node.js and npm inside the Jenkins container

Enter the Jenkins Docker container as the root user:

docker exec -u 0 -it <container_id> bash

Update packages and install curl:

apt update
apt install -y curl

Download and run the NodeSource setup script, then install Node.js:

curl -sL https://deb.nodesource.com/setup_20.x -o nodesource_setup.sh
bash nodesource_setup.sh
apt install -y nodejs

Verify the installation:

node -v   # should print v20.x.x
npm -v    # should print a version number

3. Install the Pipeline Stage View plugin

• Navigate to Manage Jenkins > Plugins > Available plugins
• Search for Pipeline Stage View, select it, and click Install
• Check Restart Jenkins when installation is complete and no jobs are running

If Jenkins does not restart automatically, start it manually:

docker ps -a
docker start <container_id>

• Navigate to Manage Jenkins > Plugins > Installed plugins to confirm the plugin is active.

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Make Docker Available on the Jenkins Server

Why? Jenkins needs access to the host Docker daemon so it can build and push images as part of the pipeline.

1. Stop the existing Jenkins container

docker ps
docker stop <container_id>

2. Start a new Jenkins container with Docker socket mounted

docker run -p 8080:8080 -p 5000:5000 -d \
  -v jenkins_home:/var/jenkins_home \
  -v /var/run/docker.sock:/var/run/docker.sock \
  jenkins/jenkins:lts

3. Enter the container as root and install Docker

docker ps
docker exec -it -u 0 <container_id> bash

Run the official Docker install script:

curl https://get.docker.com/ > dockerinstall && chmod 755 dockerinstall && ./dockerinstall

4. Grant the Jenkins user access to the Docker socket

chmod 666 /var/run/docker.sock

5. Re-enter the container as the jenkins user and verify

exit
docker exec -it <container_id> bash
docker pull redis   # should succeed if Docker access is working

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Create Jenkins Credentials for GitHub

1. Navigate to Manage Jenkins > Credentials > System > Global credentials
2. Click Add Credentials and fill in:

Field	Value
Kind	Username with password
Username	<Your GitHub username>
Password	<Your GitHub password>
Treat username as secret	Yes
ID	github

3. Click Create.

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Create a Private Docker Hub Repository

1. Log in to Docker Hub
2. Click Create Repository and fill in:

Field	Value
Name	app
Visibility	Private

3. Click Create.

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Create Jenkins Credentials for Docker Hub

1. Navigate to Manage Jenkins > Credentials > System > Global credentials
2. Click Add Credentials and fill in:

Field	Value
Kind	Username with password
Username	<Your Docker Hub username>
Password	<Your Docker Hub password>
Treat username as secret	Yes
ID	docker

3. Click Create.

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Create a Freestyle Jenkins Job

1. Create the job

• From the dashboard, click New Item (or Create a job)
• Name: freestyle
• Type: Freestyle project
• Click OK

2. Configure Source Code Management

Under Source Code Management, select Git and fill in:

Field	Value
Repository URL	https://github.com/explicit-logic/jenkins-module-8.2
Credentials	github
Branches to build	*/freestyle

3. Bind Docker credentials as environment variables

Under Build Environment, check Use secret text(s) or file(s), then click Add > Username and Password (separated):

Field	Value
Username Variable	USERNAME
Password Variable	PASSWORD
Credentials	docker

4. Add Maven test step

Click Add build step > Invoke top-level Maven targets:

Field	Value
Maven Version	maven-3.9
Goals	test
POM	app/pom.xml

5. Add Maven package step

Click Add build step > Invoke top-level Maven targets again:

Field	Value
Maven Version	maven-3.9
Goals	package
POM	app/pom.xml

6. Add Docker build & push step

Click Add build step > Execute Shell and enter:

cd app
docker build -t <docker_username>/app:freestyle .
echo $PASSWORD | docker login -u $USERNAME --password-stdin
docker push <docker_username>/app:freestyle

Replace <docker_username> with your Docker Hub username.

7. Run the job

Click Build Now and monitor the console output.

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Create a Pipeline Jenkins Job

1. Create the job

• From the dashboard, click New Item
• Name: pipeline
• Type: Pipeline
• Click OK

2. Configure the Pipeline

Scroll to the Pipeline section and fill in:

Field	Value
Definition	Pipeline script from SCM
SCM	Git
Repository URL	https://github.com/explicit-logic/jenkins-module-8.2
Credentials	github
Branches to build	*/pipeline

Jenkins will look for a Jenkinsfile at the root of the branch automatically.

3. Run the job

Click Build with Parameters and fill in:

Parameter	Value
DOCKER_REPO	<docker_username>/app:pipeline

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Create a Multibranch Pipeline Jenkins Job

1. Create the job

• From the dashboard, click New Item
• Name: multibranch
• Type: Multibranch Pipeline
• Click OK

2. Configure Branch Sources

Under Branch Sources, click Add source > Git and fill in:

Field	Value
Project Repository	https://github.com/explicit-logic/jenkins-module-8.2
Credentials	github

Click Save. Jenkins will automatically scan the repository and create jobs for branches that contain a Jenkinsfile.

3. Run the job

Click Build with Parameters and fill in:

Parameter	Value
DOCKER_REPO	<docker_username>/app

Notes:

• The Docker image tag is derived from the branch name (e.g., main, pipeline).
• The test phase runs only on the main branch.