Jenkins Fundamentals

Jenkins is an open-source automation server that orchestrates CI/CD pipelines — build, test, deploy — and it exists because before managed CI like GitHub Actions, teams needed a self-hosted, scriptable engine to run their release process on every commit. The model is a controller that manages scheduling and config plus agents that run the steps, which enables parallel execution. The modern form is pipeline as code — a Jenkinsfile checked into the repo, so the pipeline is versioned with the source and reviewable. The trade-off I'm honest about is control versus maintenance: self-hosting gives you full control — custom agents, on-prem networks, any plugin — but you bear the operations burden of upgrading the controller, managing plugin compatibility, and patching security holes. The plugin ecosystem is both Jenkins' power and its fragility; plugins enable any integration but need governance. So for teams with on-prem constraints or heavy customization needs Jenkins still makes sense; for greenfield projects, managed CI often wins because it removes the ops burden.