The CLI Terminal  The CLI terminal is a powerful tool that is often the primary method used to administer small low-power devices, extremely capable cloud computing servers, and everything in between. A basic understanding of the terminal is essential to diagnosing and fixing most Linux based systems. Since Linux has now become so ubiquitous, even those who plan on working primarily with systems not utilizing the Linux kernel can benefit from having a basic understanding of the terminal. What is a command? A command is a software program that when executed on the CLI (command line interface), performs an action on the computer. When you type in a command, a process is run by the operating system that can read input, manipulate data and produce output. A command runs a process on the operating system, which then causes the computer to perform a job. To execute a command, the first step is to type the name of the command. Type  ls  and hit  Enter . The result s...