Jenkins Installation and First Pipeline Setup on Ubuntu

Jenkins is an open-source automation server that helps with continuous integration and continuous delivery (CI/CD). This guide will walk you through the process of installing Jenkins on Ubuntu, checking system details using a Bash script, and creating your first pipeline using Jenkins' powerful pipeline functionality.

Step 1: Installing Jenkins on Ubuntu

Before we begin, ensure your system is up-to-date.

1.1 Update System Packages

First, update your system’s package list to ensure everything is up to date:

sudo apt update && sudo apt upgrade -y

1.2 Install Java

Jenkins requires Java to run. Install the default Java Development Kit (JDK):

sudo apt install openjdk-11-jdk -y

To verify the installation, use:

java -version

1.3 Add Jenkins Repository

To install Jenkins, add its official repository to your system:

wget -q -O - https://pkg.jenkins.io/jenkins.io.key | sudo tee /etc/apt/trusted.gpg.d/jenkins.asc

Next, add the Jenkins repository:

sudo sh -c 'echo deb http://pkg.jenkins.io/debian/ stable main > /etc/apt/sources.list.d/jenkins.list'

1.4 Install Jenkins

Once the repository is added, update the package list and install Jenkins:

sudo apt update
sudo apt install jenkins -y

1.5 Start Jenkins

Enable and start the Jenkins service:

sudo systemctl enable jenkins
sudo systemctl start jenkins

You can check the status of Jenkins:

sudo systemctl status jenkins

Step 2: Accessing Jenkins

Jenkins will be running on port 8080 by default. Open your browser and navigate to:

http://localhost:8080

2.1 Unlock Jenkins

To unlock Jenkins, you will need the initialAdminPassword. Retrieve it with the following command:

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

Enter the password in the browser prompt.

2.2 Install Suggested Plugins

Once you’ve unlocked Jenkins, you'll be prompted to install plugins. Choose the "Install suggested plugins" option to proceed with the default plugin installation.

Step 3: Creating Your First Jenkins Pipeline

3.1 Create a New Pipeline Project

1. After logging into Jenkins, click on New Item.
2. Enter a name for your pipeline (e.g., "First-Pipeline").
3. Select Pipeline and click OK.

3.2 Configure the Pipeline

In the pipeline configuration page, scroll down to the Pipeline section. Here, you'll define your pipeline script. For this guide, we’ll use a simple pipeline that checks system details using a Bash script.

pipeline {
    agent any

    stages {
        stage('Check System Details') {
            steps {
                script {
                    sh 'bash check_system_details.sh'
                }
            }
        }
    }
}

3.3 Create a Bash Script

In your Jenkins workspace, create a script called check_system_details.sh. This script will gather system information.

#!/bin/bash

echo "System Information:"
echo "--------------------"
hostnamectl
echo
df -h
echo
free -h
echo
uname -a

Ensure that the script has executable permissions:

chmod +x check_system_details.sh

3.4 Run the Pipeline

Save the pipeline and click Build Now to execute the pipeline. Jenkins will run the check_system_details.sh script, and you should see the system details in the build log.