Introduction to Jenkins

Jenkins is an open-source automation server that helps automate parts of software development related to building, testing, and deploying, facilitating continuous integration and continuous delivery (CI/CD). It is highly extensible, with a large number of plugins available to integrate with various tools and platforms.

Key Features of Jenkins:

1.    Extensibility: Jenkins supports a wide range of plugins for different tasks and integrations.

2.    Distributed Builds: Jenkins can distribute build tasks across multiple machines.

3.    Pipeline as Code: Define your build, test, and deploy processes in code.

4.    Easy Installation: Jenkins is easy to set up and configure.

How Jenkins Works

1.    Job Configuration:

o   A job in Jenkins is a task or set of tasks like building code, running tests, or deploying applications.

o   You configure a job by specifying the tasks and defining when and how often they should run.

2.    Source Code Management (SCM):

o   Jenkins integrates with SCM tools like Git, SVN, and Mercurial.

o   It can pull code from repositories to build and test automatically.

3.    Build Triggers:

o   Jobs can be triggered by various means, such as code changes (via webhooks), scheduled intervals (cron jobs), or manual triggers.

4.    Build Execution:

o   Jenkins executes the defined build steps, which can include compiling code, running tests, and packaging applications.

o   It supports various build tools like Maven, Gradle, and Ant.

5.    Post-Build Actions:

o   After the build, Jenkins can perform additional actions like archiving artifacts, notifying stakeholders, or deploying applications.

o   It can also integrate with tools like Slack, email, or Jira for notifications.

6.    Plugins:

o   Jenkins has a robust plugin ecosystem. Plugins can add new functionality or integrate Jenkins with other tools and platforms.

o   Examples include Docker, Kubernetes, AWS, and more.

Using Jenkins: A Step-by-Step Guide

1. Installation:

• Prerequisites:

  • Jenkins requires Java. Ensure Java is installed on your system.

    
    

• Installing Jenkins:

  • On Windows:

    • Download the Windows installer from the Jenkins website and run the setup.

  • On macOS:

    • Use Homebrew: brew install jenkins-lts

  • On Linux:

    • Use package managers like apt or yum, or download the .war file from the Jenkins website and run it using java -jar jenkins.war.

      
      

2. Initial Setup:

• Access Jenkins:

  • Once installed, Jenkins runs on http://localhost:8080.

• Unlock Jenkins:

  • During the initial setup, Jenkins will prompt you for an administrator password, found in the initialAdminPassword file.

• Install Suggested Plugins:

  • Jenkins will recommend a set of plugins. Installing these will cover most basic needs.

• Create First Admin User:

  • Set up your first administrative user with credentials.

    
    

3. Creating a Job:

• Create a New Job:

  • Go to Jenkins dashboard, click on "New Item", name your job, and select the job type (e.g., Freestyle project).

• Configure the Job:

  • Source Code Management:

    • Specify the repository URL and credentials if needed.

  • Build Triggers:

    • Set up how and when the job should be triggered (e.g., poll SCM, build periodically).

  • Build Steps:

    • Add build steps, like executing shell commands, running build tools (Maven, Gradle), or invoking other jobs.

  • Post-Build Actions:

    • Define actions like archiving artifacts, sending notifications, or triggering other jobs.

4. Defining Pipelines:

• Pipeline as Code:

  • Jenkins Pipeline allows defining the entire build process in a Jenkinsfile, written in Groovy.

• Creating a Pipeline Job:

  • Create a new item, choose "Pipeline", and define the pipeline script.

5. Running and Monitoring Jobs:

• Run Jobs:

  • Trigger the job manually or wait for it to be triggered by configured triggers.

• Monitor Jobs:

  • View job progress and logs in real-time via the Jenkins dashboard.

  • Check build history and artifact archives for previous runs.

6. Using Plugins:

• Install Plugins:

  • Go to "Manage Jenkins" > "Manage Plugins".

  • Browse and install necessary plugins to extend Jenkins functionality.

• Configure Plugins:

  • After installation, configure plugins via "Manage Jenkins" or within job configurations.