How to Use and Configure Jenkins

 

1. Install Latest JDK (OpenJDK 17+ recommended)

bash
sudo apt update
sudo apt install openjdk-17-jdk -y
java -version

• Installs OpenJDK 17.

• java -version confirms the installation.

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2. Add Jenkins Repository and Key

bash
wget -q -O - https://pkg.jenkins.io/debian-stable/jenkins.io.key | sudo apt-key add -
sudo sh -c 'echo deb https://pkg.jenkins.io/debian-stable binary/ > /etc/apt/sources.list.d/jenkins.list'
sudo apt update

• Adds Jenkins official repo and key.

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3. Install Jenkins

bash
sudo apt install jenkins -y

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4. Start and Enable Jenkins Service

bash
sudo systemctl start jenkins
sudo systemctl enable jenkins
sudo systemctl status jenkins

• Starts Jenkins and enables it to run on boot.

• status checks if Jenkins is running.

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5. Access Jenkins Web UI

• Open browser: http://<VM-IP>:8080

• Get initial admin password:

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

• Use this password to unlock Jenkins in the browser and continue setup.

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6. Jenkins CLI Commands (using jenkins-cli.jar)

a) Download Jenkins CLI

bash
wget http://<VM-IP>:8080/jnlpJars/jenkins-cli.jar

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b) List all jobs

bash
java -jar jenkins-cli.jar -s http://<VM-IP>:8080 list-jobs

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c) Trigger a build for a job

bash
java -jar jenkins-cli.jar -s http://<VM-IP>:8080 build <job-name>

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d) Get job configuration XML

bash
java -jar jenkins-cli.jar -s http://<VM-IP>:8080 get-job <job-name> > config.xml

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e) Create a new job from XML config

bash
java -jar jenkins-cli.jar -s http://<VM-IP>:8080 create-job <new-job-name> < config.xml

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f) Enable/Disable a job

bash
java -jar jenkins-cli.jar -s http://<VM-IP>:8080 disable-job <job-name>
java -jar jenkins-cli.jar -s http://<VM-IP>:8080 enable-job <job-name>

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g) Get build logs for a job

bash
java -jar jenkins-cli.jar -s http://<VM-IP>:8080 console <job-name> <build-number>




1. Configure System
Step 1: Open Jenkins dashboard


Go to http://<your-jenkins-ip>:8080


Login with admin user.


Step 2: Navigate to Manage Jenkins > Configure System


Click Manage Jenkins from the left menu


Click Configure System


Step 3: Set Jenkins URL


Under Jenkins Location → set Jenkins URL to your Jenkins server URL (e.g., http://your-jenkins-server:8080)


This URL is used in notifications and links.


Step 4: Add JDK installation


Scroll to JDK installations section


Click Add JDK


Enter name (e.g., OpenJDK 17)


Check Install automatically and select JDK version OR provide local path if installed manually


Step 5: Configure Tool Locations (optional)


For Maven, Git, Gradle, specify executable paths if Jenkins does not auto-detect.


Step 6: Configure Email Notification


Scroll to Extended E-mail Notification or E-mail Notification section


Enter SMTP server (e.g., smtp.gmail.com)


Enter default user email suffix if required


Test email sending using Test configuration by sending test e-mail


Step 7: Save changes


Click Save at the bottom.



2. Configure Global Security
Step 1: Go to Manage Jenkins > Configure Global Security


Click Manage Jenkins > Configure Global Security


Step 2: Enable Security


Check Enable security checkbox


Step 3: Configure Authentication


Select authentication method:


Jenkins’ own user database (default)


LDAP or Active Directory (if integrated with company network)




Step 4: Configure Authorization


Choose authorization strategy:


Matrix-based security: granular control over who can do what


Project-based Matrix Authorization


Logged-in users can do anything (simple)


Anyone can do anything (not recommended for production)




Step 5: Configure Agent Protocols and Security (optional)


Under Agent-to-master security subsystem, keep secure protocols enabled


Check Prevent Cross Site Request Forgery exploits


Step 6: Save configuration


Click Save



3. Manage Credentials
Step 1: Navigate Manage Jenkins > Credentials


Click Manage Jenkins > Manage Credentials


Step 2: Select domain or global credentials


Select appropriate domain (e.g., Global) or create new domain


Step 3: Add Credentials


Click Add Credentials


Choose credential type:


Username with password


SSH Username with private key


Secret text (API tokens, passwords)


Certificate




Step 4: Enter required details and save


Provide ID and description for easy identification in jobs



4. Manage Plugins
Step 1: Go to Manage Jenkins > Manage Plugins


Click Manage Jenkins > Manage Plugins


Step 2: Install new plugins


Open Available tab


Search and select plugins (e.g., Git, Pipeline, Docker plugins)


Click Install without restart or Download now and install after restart


Step 3: Update existing plugins


Open Updates tab


Select plugins to update and click Download now and install after restart


Step 4: Plugin management


Enable/disable installed plugins from Installed tab



5. Manage Nodes and Clouds (Agents)
Step 1: Go to Manage Jenkins > Manage Nodes and Clouds


Click Manage Jenkins > Manage Nodes and Clouds


Step 2: Add new node


Click New Node


Enter node name, select Permanent Agent, click OK


Step 3: Configure node


Enter remote root directory (e.g., /home/jenkins)


Set number of executors (parallel jobs it can run)


Set labels for job assignment


Choose launch method (SSH is recommended)


Provide SSH host, credentials, and test connection


Step 4: Save node configuration


Click Save



6. System Logs and Monitoring
Step 1: Go to Manage Jenkins > System Log


View Jenkins runtime logs here


Add Log Recorders to track specific classes/packages for debugging


Step 2: Load statistics


View executor load and system resource consumption



7. Using Script Console
Step 1: Manage Jenkins > Script Console


Execute Groovy scripts for administration tasks


Example: List all jobs
groovy
Jenkins.instance.getAllItems(Job.class).each { println it.name }




Summary Tips


Always backup Jenkins config files (usually in /var/lib/jenkins) before major changes.


Regularly update Jenkins core and plugins for security and features.


Use credentials plugin to securely manage secrets.


Use matrix-based security for fine-grained user permissions.


Label nodes properly to assign jobs efficiently.