Enterprise Jenkins

Jenkins is the "Grandfather" of CI/CD. While others move to the cloud, Jenkins remains the king of On-Premise and Customizable pipelines. Understanding its distributed architecture is key to scaling big builds.

1. Master-Agent Model

• Master: The brain. Handles the UI, schedule, and job definitions. It does NOT run the code.
• Agents (Nodes): The muscle. These are separate servers (Linux, Windows, Docker) that actually execute the builds.

2. Jenkinsfile & Declarative Pipelines

Gone are the days of "clicking buttons" in the UI. We use Pipeline as Code. The Jenkinsfile defines the stages (Build, Test, Deploy) and is versioned in Git. This makes your CI configuration audit-able and reproducible.

4. Interview Mastery

Q: "Why would you choose Jenkins over GitHub Actions today?"

Architect Answer: "I choose Jenkins when I have **Complex, Multi-step Dependencies** that GitHub Actions can't handle, or when the code must stay entirely **Air-gapped** from the internet for security reasons. Jenkins has 1,500+ plugins, allowing it to talk to legacy mainframes, hardware labs, and custom internal tools that cloud-based CI/CD simply can't reach."