Although people often refer to Linux as an operating system, it is actually a kernel. In computer science, a kernel is software responsible for booting the system. The kernel loads drivers to recognize attached devices (such as a keyboard, mouse, display, and so on), and manages software processes. Linux was initially started by Linus Torvalds in 1991, then a computer science student in Finland.

Torvalds made the kernel available to everyone by using the GNU General Public License (GPL) to license the code. This licensing mode ensures that the licensed code can be used for any purpose, as long as public changes are contributed back to the project. After Torvalds announced the project to other developers on the Internet, programmers from all over the world contributed code to the Linux kernel. Among those early contributors was Red Hat, which has contributed to the development of the Linux operating system since 1993.

In 1998, Christine Peterson coined the term open source to describe code that was built collaboratively and shared freely.

Linux gained popularity among developers because all its code was available to study, modify, and share. Linux was adopted by systems administrators all over the world. The Linux kernel, combined with applications written by the Gnu's Not UNIX (GNU) project, was similar to the existing UNIX server operating system, but ran on commodity hardware.

Today, Linux is available to any user who wants to run it, and any developer who wants to build it. It is common on servers, in the cloud, on desktops and laptops, and on consumer devices such as Android, Chromebooks, and the Steam Deck.

When you power on a computer, a chip on the motherboard that is loaded with firmware searches for a hard drive that contains an application called a boot loader. A boot loader is software that loads the operating system code into memory for its execution.

After the computer locates the boot loader, the boot loader takes control over the boot process and locates the kernel. The kernel is loaded into memory, probes the hardware, and loads the appropriate drivers for the computer hardware it detects. The service manager launches and provides networking, graphics, sound, a login screen, and so on.

After the boot process is complete, the kernel continues to run in the background, but you are presented with a login prompt so that you can open an interface to the applications on the computer. On Linux, you have access to two interfaces. The Graphical User Interface (GUI) is a point-and-click interface in which data is represented by icons and visual displays. The shell, sometimes also called a terminal or a console, is a text-only prompt that allows you to type and run commands.

Many Linux users make frequent use of both interfaces. The GUI provides the familiar conventions of a desktop, such as icons for files and folders, menus, and so on. The shell is efficient, programmable, and faster than using a GUI over a network. This course teaches both.

Individuals and companies build Linux from its constituent parts and then distribute it online for others to use. When you download Linux as an operating system, you are downloading a distribution of Linux. A distribution (often called a distro for short) is a distinct build of the Linux operating system, and can be produced by anyone with the skills and need to create one.

Most distributions are built for a specific purpose. For example, Raspberry Pi is a low-powered embedded system the size of a credit card, so it runs a Linux distribution that provides only the special drivers and services required by its hardware.

There is even less software in Red Hat's Universal Base Image (UBI) because it is used as the foundation for cloud services that do not require the libraries that physical computers do. By contrast, the Fedora distribution contains drivers for the latest consumer hardware to ensure that printers, sound cards, graphic cards, webcams, and other peripherals function as expected.

The most prominent distributions of Linux tend to be those produced consistently and reliably. Some distributions are supported by businesses like Red Hat, while others are volunteer efforts. Popular Linux distributions include the following projects:

Changing between Linux distributions is a little like getting a new mobile phone. The basic concepts transfer, but you might have to learn which application to use to install apps, where the button is to join a network, how to change a specific setting, or how to log out.

This course will help you become familiar with Linux technologies that are common across many Linux systems, whether you use Linux on your laptop or as a container running on an OpenShift cluster in the cloud. You will learn how to interact with the desktop, as well as the essential commands you need to work efficiently in a Linux terminal.