Domain Name Servers (DNS) are the Internet’s equivalent of a phone book. They maintain a directory of domain names and translate them to Internet Protocol (IP) addresses. Quad9 is a free, recursive, anycast DNS platform that provides end users robust security protections, high-performance, and privacy. When you use Quad9, attackers and malware cannot leverage the known malicious domains to control your systems, and their ability to steal your data or cause harm will be hindered. Quad9 is an effective and easy way to add an additional layer of security to your infrastructure for free. This page explains how to setup Quad9 DNS on an Arch Linux, a CentOS/Fedora/RHEL, and Ubuntu/Debian Linux by editing various files.