Foundations: What's Linux?

- Linux is an operating system, that runs on a huge range of devices, from smartphones to smart home devices to laptop and desktop computers, mainframes, supercomputers and even the infrastructure, that routes data across the internet. Linux is a popular choice for hosting web servers and it's extremely well represented in the enterprise, running mission-critical servers and systems. Many major corporations and governments use Linux exclusively or in combination with other operating systems, although only about 2% of computer users use Linux as their desktop environment, over half of the world's smartphones run operating systems derived from Linux and the great majority of the world's supercomputers run Linux as well.

When you start looking for it, Linux is everywhere, in point of sale systems, telephone switching networks, industrial control systems and even some cars, TVs and cable boxes run Linux. How does one operating system run on such a wide range of devices? The answer is at the very heart of Linux, a component called the kernel, the kernel is the core of what makes Linux Linux, it's a piece of software under constant development and improvement, that communicates with a computing hardware, whether that's in a smartphone, a car or a supercomputer and it provides an interface for software to hook onto, allowing that software to operate on this wide range of hardware.

Different systems have different software, that hooks onto the kernel and the kernel code is assembled in different ways for different kinds of hardware, but it's the same basic structure and system, regardless of where it's running. Linux got started as a response to restrictive licensing of a Unix-like operating system, Linus Torvalds developed the initial kernel and distributed it in 1991, he still primarily directs the development of the kernel, though other people and organizations make contributions and improvements as well, but Linux is more than just the kernel itself, tools and software that make up the ecosystem, that allows Linux to be so flexible and useful come in large part from the GNU project, that's G-N-U, which stands for GNU is Not Unix.

The GNU project was started by Richard Stallman, in order to create a Unix-compatible software system composed of free software or software that was not burdened by restrictive licensing and could be freely used and modified by users as needed. These GNU tools and the Linux kernel made a powerful combination, a complete operating system that is at its heart free. The kernel code and the code for the GNU tools and much of the other code that makes up the Linux ecosystem is open source, which means that the source code, that gets built into the programs that we use is available for anyone to look at, to read, to learn from, and to suggest changes too.

While most of this code is extremely complex and takes a detailed study to understand, an important part of open source is the philosophy and the community, as much as it is the nuts and bolts of making a change to the code. The Linux operating system, combining both the kernel and basic tools that make up its primary ecosystem is considered Unix-like, meaning that it follows many of the conventions of the Unix standards, that the tools work in a similar way and that it follows certain philosophies behind Unix.

Some aspects of this Unix philosophy, that you'll notice as you explore Linux are the idea that tools should be small, that they should do one thing and do it well and that these tools should communicate with each other using text, rather than custom binary formats, that's why when we're using tools at the command line, we pipe the output of one tool into the next as text, rather than having one big Swiss Army Knife tool, that tries to do everything at once. There are other Unix standards that Linux emulates and we'll see some of those as we explore more corners of the Linux world.

Linux is represented by a penguin, who's name is Tux, as the mascot for Linux, Tux appears in many places from many system boot screens, where one Tux image shows up for each processor in the system to countless stickers, stuffed toys, T-shirts and anything else that Linux fans can print him on. Tux was designed by Larry Ewing. Linux is very popular with software development professionals and enthusiasts, who enjoy getting their hands dirty working with the mechanics of the kernel and adding support for new hardware, it's also popular with system administrators and users who appreciate the power and flexibility of the operating system and the tools in its ecosystem and hobbyists with computers like the Raspberry Pi enjoy being able to run a lightweight, flexible operating system, that they can use for their projects, some Linux users use it because it's free and it works on low-cost hardware and that's all they can afford, other users use it because they have high-end hardware and Linux lets them squeeze all of the potential out of their systems, some users prefer to use free and open source software and still others use Linux, because it helps them not worry about common security threats faced by users of other popular operating systems.

On a Linux machine, you can switch the Desktop Manager, the Window Manager, the Command Shell and more. Linux is great for customizing your computing experience. To be a Linux enthusiast, you don't have to understand the code that makes up the kernel or know all of the command line shell options or be able to draw a diagram of the system boot process and you don't even have to have a penguin sticker on your laptop, you just have to be interested in Linux.