Linux servers are renowned for their stability, cost-effectiveness, and open-source nature. However, ensuring security is of utmost importance due to ever-evolving cyber threats and attacks. This guide presents an ultimate Linux server security checklist that covers essential steps to harden and secure a Linux server, providing explanations on the importance of each step and how it helps maintain system integrity and safeguard valuable data. We encourage you to use this checklist as a reference for achieving ultimate security on their Linux servers. The steps are sorted from most important to least important.