Jenkins Setup in AWS EC2

1. The Big Picture: Jenkins & Docker Slaves

Before the steps, here is the “gist” of how this architecture functions:

• The Jenkins Controller (Master): This is your main EC2 instance. it doesn’t do the “heavy lifting.” Instead, it manages the UI, schedules jobs, and tells the “Slaves” what to do.
• The Docker Slaves (Agents): These are the workers. In a modern setup, these aren’t necessarily separate permanent machines. When a build starts, Jenkins uses the Docker Pipeline Plugin to spin up a temporary Docker container on the same EC2 or a remote one.
• Where they run: They run as containers. Once your code is built and tested inside that container, Jenkins destroys the container, keeping your main server clean and “stateless.”

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2. Step-by-Step Installation (2026 Version)

Phase A: Install Java 21 (LTS)

Jenkins is a Java application. We use Java 21 for better performance and long-term support.

sudo dnf update -y
sudo dnf install java-21-amazon-corretto-devel -y

java -version

Phase B: Install Jenkins

We now use the specific keyrings directory for better security management in Ubuntu.

# 1. Download the Jenkins repository configuration
sudo wget -O /etc/yum.repos.d/jenkins.repo \
    https://pkg.jenkins.io/redhat-stable/jenkins.repo

# 2. Import the GPG key for security
sudo rpm --import https://pkg.jenkins.io/redhat-stable/jenkins.io-2023.key

# 3. Upgrade and install Jenkins
sudo dnf upgrade -y
sudo dnf install jenkins -y

# 4. Enable and start Jenkins service
sudo systemctl enable jenkins
sudo systemctl start jenkins

Phase C: AWS Network Setup

1. Go to EC2 Console > Security Groups.

2. Edit Inbound Rules for your instance’s group.

3. Add Rule: Custom TCP | Port 8080 | Source My IP (Preferable for security) or 0.0.0.0/0.

4. OS Firewall (If enabled): RHEL often has firewalld active.

   sudo firewall-cmd --permanent --add-port=8080/tcp sudo firewall-cmd --reload

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3. Initial Setup & Docker Integration

Unlock Jenkins

1. Access http://<your-ec2-ip>:8080.

2. Get the password:

   sudo cat /var/lib/jenkins/secrets/initialAdminPassword

3. Select Install Suggested Plugins.

4. Create your Admin User.

Install Docker & Grant Permissions

To use Docker as a slave, Jenkins needs permission to talk to the Docker engine.

# Install Docker (Amazon Linux 2023 / RHEL 9)
sudo dnf install docker -y

# Start and Enable Docker
sudo systemctl enable docker
sudo systemctl start docker

# Add users to the docker group
sudo usermod -aG docker jenkins
sudo usermod -aG docker ec2-user  # Or 'cloud-user' depending on the AMI

# Reload the Jenkins service to recognize the new group membership
sudo systemctl restart jenkins

Install “Docker Pipeline” Plugin

1. In Jenkins UI: Manage Jenkins > Plugins > Available Plugins.
2. Search for “Docker Pipeline”.
3. Install it and check the box to Restart Jenkins when done.

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4. How to use it (The “New” Way)

You no longer need to manually “configure” a slave in the settings for every job. Just use a Jenkinsfile like this:

pipeline {
    agent {
        docker { image 'node:20-alpine' } // This spins up a 'Slave' container automatically
    }
    stages {
        stage('Build') {
            steps {
                sh 'node -v'
            }
        }
    }
}