Merlijn van Deen created a Vagrant system to let you easily replicate the CI infrastructure and known as mkjenkins. It is a script to quickly get a Wikimedia Foundation Jenkins mirror running. It downloads Jenkins, Jenkins job builder and relevant configuration, builds JJB jobs and pushes them to Jenkins.
In addition, it prepares the directory structure for some assumptions the current jobs make - such as /var/lib/jenkins being available and writable. It is symlinked to $HOME/.jenkins/var/lib/jenkins, but this means you need local root (or you can't make the symlink, and not all jobs will function).