Static IP addresses are an important part of networking for many types of servers, although a bit more overhead to configure they ensure a consistent state. The Ubuntu configuration of static addresses varies depending on the operating system version you are running, this guide will look at the 2 most recent versions with Long Term Support (LTS)
This guide shows you how to configure a static IP address on an Ubuntu server running 16.04 LTS or 18.04 LTS that is currently configured with DHCP.