Linux Command Line The Linux command line provides a way to manually interact with the Linux operating system. The shell program is a program that acts as an interface between the user and the rest of the Linux operating system, including the kernel. The shell displays the shell promp t. Users enter commands at this prompt. By default, the shell display one of two prompts, depending on the type of user logged in. For root users, the prompt is the # symbol: For non-root users, the prompt is the $ symbol: The shell accepts the commands and processes it. The Linux command line refers to commands entered at the shell prompt. The command line ends when you hit the Enter key. A command line however can be extended beyond a single line. I.e. if the command line is longer than one line, you can use the backslash to extend the command line to two or more lines, e.g. sudo