Jenkins 8,793 ships as a .war file, native packages for Debian 319 , Red Hat and Windows, a Homebrew 6,457 formula, a Helm 29,435 chart and a Docker 514 image. This book uses the image: it pins Java and the Jenkins version together, keeps the controller off the host's package manager, and turns an upgrade into "pull a new tag and recreate the container," with all state in one volume. Everything in How Builds Run and Surviving Restarts ran on the controller installed here.