Moving Jenkins Pipelines to GitHub Actions: What Maps Directly and What Needs Rewriting

The article explains how to migrate Declarative Jenkinsfile pipelines to GitHub Actions by translating directives one by one, such as agent becoming runs-on and when becoming if. It notes that plugin steps, shared libraries and Groovy script blocks cannot be converted automatically and must be rebuilt by hand. It recommends moving simple build-and-test pipelines first and deploy pipelines last, keeping the Jenkins job running until the new workflow produces matching results. A key warning is that each GitHub Actions job runs on its own fresh machine without a shared workspace, which changes behavior more than the syntax does. The piece presents a mapping table of sixteen constructs, flagging which convert cleanly and which change how the pipeline behaves.