What Is the Linux Operating System? A Complete Introduction

Linux is an open-source, Unix-like operating system kernel first released in 1991 by Finnish software engineer Linus Torvalds. Today, Linux is the most widely deployed operating system on the planet — powering Android smartphones, web servers, cloud infrastructure, supercomputers, embedded systems, and increasingly, enterprise desktops. If you use the internet, stream video, or use a smartphone, you interact with Linux every day.

What Is an Operating System?

An operating system (OS) is the software layer between hardware and applications. It manages the CPU, memory, storage, and peripheral devices, and provides a stable interface for applications to run without needing to know the specifics of the underlying hardware. Without an operating system, running multiple applications on a computer would require each application to directly manage hardware — an impossibility at scale.

Linux provides this OS layer. Specifically, “Linux” refers to the kernel — the core of the OS that manages hardware resources. The complete operating system most users interact with combines the Linux kernel with software from the GNU Project and other sources, which is why you will sometimes see it referred to as GNU/Linux.

How Did Linux Start?

In August 1991, Linus Torvalds posted to the Usenet group comp.os.minix: “I’m doing a (free) operating system (just a hobby, won’t be big and professional like gnu) for 386(486) AT clones.” What started as a hobby project grew into the most important piece of software infrastructure in the world.

Torvalds licensed the Linux kernel under the GNU General Public Licence (GPL), meaning anyone could use, study, modify, and distribute it — provided that derivatives remained open source. This decision enabled a global community of developers to contribute, which accelerated Linux’s development far beyond what any single company could have achieved.

Linux Distributions — What Are They?

Because the Linux kernel alone is not a complete OS, developers and organisations package it with applications, libraries, package managers, and installers to create distributions (or “distros”). Each distribution makes different choices about what to include, how to configure defaults, and what use cases to optimise for.

Major Linux distributions include:

• Ubuntu — the most popular desktop and server distribution, with excellent hardware support and a large community
• Red Hat Enterprise Linux (RHEL) — the enterprise standard, used by large organisations requiring commercial support and long-term stability
• Debian — one of the oldest distributions, known for stability; the upstream for Ubuntu
• Rocky Linux / AlmaLinux — free, community-supported RHEL alternatives that emerged after CentOS changed direction
• Arch Linux — a minimal, rolling-release distribution for advanced users who want full control
• Fedora — a cutting-edge distribution sponsored by Red Hat, featuring the latest software

How Linux Works — The Architecture

Linux follows a layered architecture:

1. Hardware — physical CPU, RAM, storage, and peripherals
2. Kernel — manages hardware resources, handles system calls from applications, and provides core services (process management, memory management, file systems, networking)
3. Shell — command-line interface for user interaction (Bash, Zsh, Fish)
4. System libraries — shared code used by applications (glibc, libstdc++)
5. Applications — user-facing software (web browsers, servers, text editors)

The separation between kernel and user space is fundamental to Linux’s stability. A crashing application cannot bring down the kernel. A kernel bug can crash the system, but kernel-level bugs are extremely rare in production-grade Linux distributions.

Where Is Linux Used?

• Web servers — Apache and Nginx, both Linux-native, power over 80% of the world’s websites
• Cloud infrastructure — AWS, Azure, and GCP all run primarily on Linux. Most cloud VMs default to Linux.
• Android — Google’s Android OS is built on the Linux kernel
• Supercomputers — 100% of the top 500 supercomputers in the world run Linux
• Embedded systems — routers, smart TVs, IoT devices, and industrial equipment
• Developer workstations — preferred by software developers globally for its tools, performance, and flexibility

Linux vs Windows vs macOS

Linux, Windows, and macOS are the three dominant OS families. Windows dominates consumer desktops. macOS dominates high-end creative and developer workstations. Linux dominates everything else — servers, cloud, embedded, and supercomputing — and is growing rapidly in developer desktop use through distributions like Ubuntu and Fedora.

Linux’s primary advantages are cost (free and open source), performance, security, stability, and the ability to run on any hardware from a Raspberry Pi to a 128-core server. Its primary challenge for mainstream desktop adoption is software compatibility — the major creative and gaming applications available for Windows and macOS do not always have Linux equivalents, though this gap has narrowed significantly with tools like Proton for gaming and cross-platform application development.