Top Jenkins Interview Questions and Answers

This section provides answers to frequently asked Jenkins interview questions, covering core concepts and practical aspects of using Jenkins for continuous integration/continuous delivery (CI/CD).

What is Jenkins?

Jenkins is an open-source automation server written in Java. It's primarily used for continuous integration and continuous delivery (CI/CD). It monitors version control systems (like Git) and triggers automated builds and tests when changes are detected.

Jenkins vs. Maven/Ant

Maven and Ant are build tools (they automate the compilation, testing, and packaging of software). Jenkins is a CI/CD tool that orchestrates and automates the entire build, test, and deployment process.

SCM Tools Supported by Jenkins

Jenkins integrates with many source code management (SCM) tools:

  • AccuRev
  • CVS
  • Subversion
  • Git
  • Mercurial
  • Perforce
  • ClearCase
  • RTC

Continuous Integration in Jenkins

Continuous integration (CI) is a development practice where developers integrate code changes frequently into a shared repository. Each integration is verified by an automated build and automated tests. This helps catch integration issues early.

Hudson and Jenkins

Jenkins was originally known as Hudson. The name changed due to a governance dispute within the project.

Requirements for Using Jenkins

To use Jenkins, you'll need:

  • An accessible source code repository (like Git).
  • A build script (e.g., Maven pom.xml) in your repository.

Advantages of Jenkins

  • Early bug detection.
  • Extensive plugin support.
  • Automated build and testing.
  • Integration with various tools (e.g., LDAP, email servers).
  • Supports Agile and test-driven development.

Preventing Build Breaks in Jenkins

  1. Perform a successful local build (with all tests passing).
  2. Review your code changes carefully.
  3. Commit all changes to the repository.

Moving Jenkins Between Servers

You can move or copy Jenkins jobs by copying the job's directory from one Jenkins installation to another. You can also create clones of jobs by copying the directory and renaming it.

Manually Starting Jenkins

Use either (Jenkins_url)/restart (forces a restart immediately) or (Jenkins_url)/safeRestart (waits for running builds to complete) to manually restart the Jenkins service.

Useful Jenkins Plugins

  • Maven 2 project
  • Amazon EC2 plugin
  • HTML Publisher
  • Copy Artifact
  • Join plugin
  • Green Balls plugin

Creating Jenkins Backups

Back up your Jenkins configuration by copying its home directory. This directory contains all settings, build artifacts, and logs.

Cloning a Git Repository in Jenkins

[Describe how to configure Jenkins to clone a Git repository. This would involve setting up credentials for the Git repository in Jenkins and configuring a job to use those credentials to clone the repository.]

Setting Up Jenkins Jobs

  1. Select "New Item".
  2. Enter a job name and choose "Freestyle project".
  3. Click "OK".
  4. Configure the job settings (source code, build script, etc.).

Key Jenkins Integrations

Jenkins primarily integrates with:

  • Version control systems (like Git, SVN)
  • Build tools (like Maven, Ant, Gradle)

Further Reading: