Cumulus Linux is an open network operating system (ONOS) for network switches and routers that is designed to be easy to use, scale, and customize. Cumulus Linux is used by some of the world's largest cloud and data center operators. Its features include standard networking functions like routing, bridging, and VLANs, as well as advanced routing features like IP unnumbered and auto BGP. It comes with secure defaults and can be further secured to meet corporate, regulatory, and governmental standards. It is built for automation first, with end-to-end automation for continuous integration and continuous delivery (CI/CD) workflows. This introductory course provides invaluable insights into the basics of Cumulus Linux, how to get started in setting up the software and fundamental configurations.