Linux
Linux is a family of open-source Unix-like operating system kernels first released by Linus Torvalds in 1991. Unlike Windows or macOS, Linux itself is just the kernel -- the core software that manages hardware, memory, and processes -- and is almost always paired with the GNU toolset and packaged into a complete OS called a distribution (or distro).
Distributions
There is no single 'Linux operating system' -- instead, hundreds of distributions repackage the kernel with different tools, package managers, and defaults:
- Ubuntu -- beginner-friendly, based on Debian, widely used on servers and desktops
- Debian -- one of the oldest and most stable distributions
- Arch Linux -- minimal, rolling-release, popular with advanced users
- Fedora -- sponsored by Red Hat, tracks upstream software closely
- Alpine Linux -- extremely lightweight, common in Docker containers
Features
- Free and open-source under the GNU General Public License
- Runs on everything from smartwatches and routers to the majority of the world's web servers and all of the top 500 supercomputers
- Highly customizable package managers (apt, pacman, dnf, apk)
- Strong multi-user permissions model inherited from Unix
History
Linus Torvalds announced the project in a 1991 Usenet post as 'just a hobby, won't be big and professional like GNU'. It has since become the dominant operating system for servers, cloud infrastructure, and embedded devices worldwide.