Linux is an open source, Unix-like operating system developed by Linus Torvalds and released in 1991. It implements the core functionality of an operating system – the Linux kernel, which deals with things like process scheduling, memory management, networking and file system functionality and provides low-level APIs, mainly in the form of syscalls. Linux becomes a full-fledged operating system when bundled with an init system, the C standard library, command-line utilities, a package management system, and other software that often comes from the GNU project. These bundles are called Linux distributions and include names like Debian, Ubuntu, Red Hat Enterprise Linux, and Amazon Linux. Today Linux distributions dominate many computing markets: web servers, supercomputers, and embedded systems. Android and Chrome OS are two other popular operating systems based on the Linux kernel.
Links: www.kernel.org, Linux (Wikipedia).
Here's 3 amazing resources to learn Linux:
Linux Journey (linuxjourney.com)
free • resource • by Cindy Quach • 2017
This is a great introductory tutorial on Linux that briefly covers all the important topics including the shell, user management, the filesystem, processes, packages, networking, and much more. Start here if you're new to Linux or looking for an introduction to a particular Linux topic.
The Linux Programming Interface (man7.org)
paid • book • by Michael Kerrisk • 2010
This book is the best reference on Linux and Unix programming. It's monumental - 1552 pages covering system calls, library functions, and other Linux interfaces. But it is also an enjoyable read and an excellent resource for learning how various parts of Linux work.
Linux Kernel Development, 3rd edition (www.amazon.com)
paid • book • by Robert Love • 2010
If you want to be able to hack on the Linux kernel or just to understand how Linux really works under the hood, this is the book for your. You'll see how Linux implements process scheduling, memory management, system calls, the virtual filesystem, and other OS components. Above all, you'll learn how to work with the Linux source code so you can answer any Linux questions without relying on others' interpretations. Despite the highly advanced topic, it's a fun and accessible read.