Introduction to Linux

Chapter 1 — What is Linux?

If you've ever used a smartphone, streamed a film, searched the web, or paid with a card at a till, you've already relied on Linux — whether you knew it or not. Linux powers more of the world's computers than any other operating system, yet most people have never intentionally installed it. This chapter explains what Linux actually is, where it came from, and why millions of people choose it for everything from writing documents to running the internet.

Don't worry about the jargon. This chapter introduces a few technical terms — kernel, distro, open source — but each one is explained as we go. By the end you'll have a solid mental model of how Linux fits together, which makes everything in the later chapters much easier to follow.

1. A Brief History

To understand Linux you need to know a little about what came before it.

  • 1969
    Unix is born at Bell Labs (AT&T). It was a powerful, multi-user operating system written by researchers for researchers. Influential but expensive — universities could get it cheaply, but ordinary people couldn't.
  • 1983
    Richard Stallman launches the GNU Project — a plan to build a completely free (as in freedom) Unix-like operating system from scratch. GNU created many essential tools (the compiler, text editor, shell) but never finished its own kernel — the core component that talks to the hardware.
  • 1991
    Linus Torvalds, a 21-year-old Finnish student, posts a message to an internet newsgroup: "I'm doing a (free) operating system (just a hobby, won't be big and professional like gnu)". He was writing a kernel for his new PC. That kernel became Linux.
  • 1992
    GNU + Linux kernel combine to create a complete, free operating system. The GNU tools gave Linux its software; the Linux kernel gave GNU its missing piece.
  • 1990s
    Distributions appear — Slackware, Debian, Red Hat. Groups of developers package the kernel, GNU tools, and additional software into something ordinary people can actually install.
  • 2004
    Ubuntu launches, built on Debian, with a mission to make Linux accessible to everyone. It becomes the most popular desktop Linux distro and the one most beginners start with today.
  • Today
    Linux runs everywhere — 96% of the world's top web servers, all 500 of the world's fastest supercomputers, Android phones, smart TVs, in-car systems, and the computers on the International Space Station.
The name "Linux" is a blend of Linus (Torvalds) and Unix. Linus originally wanted to call it "Freax" but the administrator of the server where he uploaded it renamed the folder "Linux" — and the name stuck. The mascot, Tux the penguin, was chosen because Linus was once bitten by a penguin at a zoo and thought they were "cuddly in a geeky way."

2. The Kernel vs the Operating System

People often say "Linux" when they mean "a Linux-based operating system." Technically, Linux is just the kernel — and the distinction matters.

What is the kernel?

The kernel is the core program that sits between your software and your hardware. When a program wants to read a file, play a sound, or send data over the network, it asks the kernel — which translates that request into instructions the hardware understands. The kernel is always running, always in control, and users never interact with it directly.

What is the full operating system?

An operating system is the kernel plus everything built on top of it: a file manager, a desktop, a web browser, a text editor, system tools, and so on. When you install Ubuntu or Fedora, you're installing the Linux kernel bundled with hundreds of other programs that together form a usable system.

GNU/Linux: Purists sometimes insist on calling it "GNU/Linux" to credit the GNU Project's tools that fill out the OS. Both terms refer to the same thing — most people just say "Linux" and everyone knows what they mean.

3. Open Source and Free Software

Linux is open source. This means the source code — the human-readable instructions that make up the program — is publicly available for anyone to read, study, modify, and distribute. This is radically different from Windows or macOS, where the source code is a closely guarded secret.

What "free" actually means

In Linux circles, "free" has two distinct meanings, often summarised as "free as in speech" and "free as in beer."

  • Free as in speech (libre) — you have the freedom to use, study, modify, and share the software. This is the important one.
  • Free as in beer (gratis) — it costs nothing. Most Linux distros are also free to download, though some enterprise versions (like RHEL) charge for support.

Why does open source matter to you?

  • Security — anyone can audit the code and find vulnerabilities. Bugs get fixed faster because thousands of developers can see and fix them.
  • No lock-in — if the company behind your software disappears or changes direction, the community can carry it on.
  • Transparency — you know exactly what the software does. No hidden telemetry, no secret data collection baked in by design.
  • Cost — no licence fees, no per-seat charges, no subscription just to keep using your own computer.
You don't need to read code to benefit from open source. The fact that someone can check the code is what matters. Most Windows and macOS users never read their source code either — but with proprietary software, nobody outside the company is allowed to.

4. What is a Distribution (Distro)?

Nobody installs "the Linux kernel" on its own — it's just an engine with no body. A distribution (or distro) is a complete package: the kernel, a desktop environment, a set of pre-installed applications, a package manager for installing more software, and an installer to set it all up on your computer.

Think of it like this: the Linux kernel is the engine. A distro is the whole car — bodywork, seats, dashboard, and all — built by different manufacturers to different designs, all using the same engine underneath.

Why are there so many distros?

Because anyone can take the kernel and build a distro from it. Some are built by companies (Ubuntu by Canonical, Fedora by Red Hat), some by communities (Debian, Arch Linux), and some by individuals. Different distros make different choices about:

  • Which desktop to include — GNOME, KDE, XFCE, and others
  • How software is installed — apt, dnf, pacman, and other package managers
  • How often it updates — stable (releases every 2 years) vs rolling (constantly updated)
  • Who it's aimed at — beginners, power users, servers, specific hardware
How many distros are there? Hundreds — possibly over a thousand if you count every variant. The good news: the core skills you learn on one distro transfer to most others. The terminal commands, the file system layout, and the general concepts are the same everywhere. Chapter 2 will help you pick the right one to start with.

The main distro families

Most distros descend from a handful of "parent" distros. Knowing the family helps because distros in the same family share the same package manager and many conventions:

  • Debian family — Debian → Ubuntu → Linux Mint, Pop!_OS, Zorin OS, Raspberry Pi OS. Uses the apt package manager. The largest family; great for beginners.
  • Red Hat family — Red Hat → Fedora → CentOS/AlmaLinux/Rocky Linux. Uses dnf (formerly yum). Dominant in enterprise and server environments.
  • Arch family — Arch Linux → Manjaro, EndeavourOS. Uses pacman. Rolling release; cutting-edge but requires more hands-on management.
  • SUSE family — openSUSE Leap (stable) and Tumbleweed (rolling). Uses zypper. Strong in Europe and enterprise settings.
  • Independent — Slackware, Gentoo, NixOS. Their own package systems; generally for advanced users.

5. Linux vs Windows vs macOS

Linux
  • Free to download and use
  • Open source — fully transparent
  • Hundreds of distros to choose from
  • Highly customisable
  • Excellent for programming and servers
  • Longer learning curve initially
  • Some hardware/software compatibility gaps
  • Strong community support
Windows
  • Licence cost built into most PCs
  • Closed source — proprietary
  • One version (Home/Pro/Enterprise)
  • Limited customisation
  • Broadest hardware/software compatibility
  • Familiar to most users
  • More targeted by malware
  • Increasing advertising and telemetry
macOS
  • Tied to Apple hardware (expensive)
  • Closed source — Unix-based underneath
  • Single, polished version
  • Limited customisation
  • Strong creative/media software ecosystem
  • Very stable and well-integrated
  • Less targeted by malware than Windows
  • Apple controls the full stack
You don't have to choose one forever. It's perfectly normal to run Linux alongside Windows (dual-boot) or inside a virtual machine. Chapter 3 covers both approaches. Many people start by trying Linux in a virtual machine with no risk to their existing setup.

6. Why Do People Choose Linux?

People come to Linux for many different reasons. Here are the most common:

An old PC with a new life

Windows 11 dropped support for a huge range of older hardware. Linux runs well on machines that Windows would leave behind — a ten-year-old laptop with 4 GB of RAM can run a lightweight Linux distro like Linux Mint XFCE perfectly well, breathing years more useful life into hardware that would otherwise go to landfill.

Privacy and control

Windows 11 ships with advertising IDs, Cortana telemetry, OneDrive integration, and various data-collection features that are difficult or impossible to fully disable. Linux collects nothing by default. Your computer does what you tell it, not what a corporation decided is good for their business model.

Software development

Most professional development tools — web servers, databases, containers, cloud infrastructure — run on Linux. Developing on Linux means your local environment matches production. Most online tutorials, Docker images, and cloud VMs assume Linux. Many developers find Linux simply removes friction.

Security

Linux has a strong security model built in. User permissions, process isolation, and the package manager system (installing software from verified repositories rather than random websites) dramatically reduce the risk of malware. Linux desktops very rarely need antivirus software.

Cost

A full Linux installation — OS, office suite, image editor, video editor, and hundreds of other applications — costs nothing. For schools, charities, small businesses, and individuals, this matters.

Curiosity and learning

Linux teaches you how computers actually work. The terminal, the file system, the process model — understanding these things makes you a better user of any operating system, and they're all there to explore on Linux.

7. Linux is Already in Your Life

You may be surprised to discover how many things you use every day run Linux:

📱
Android
Android is built on a modified Linux kernel. About 3 billion active devices.
🌐
Web servers
Google, Facebook, Amazon, Wikipedia — virtually all major websites run on Linux.
🖥️
Supercomputers
All 500 of the world's fastest supercomputers run Linux.
📺
Smart TVs
Most smart TVs — Samsung, LG, Sony — run Linux under the hood.
🚗
Cars
Tesla, BMW, Toyota infotainment and control systems use Linux.
🛰️
Space
The ISS, SpaceX Falcon 9, and NASA's Mars helicopters all run Linux.
🎮
Gaming
The Steam Deck runs SteamOS, a Linux-based gaming OS.
🏦
Banking
ATMs, stock exchanges, and banking systems overwhelmingly run Linux.
☁️
The cloud
AWS, Google Cloud, and Azure all run primarily on Linux servers.

8. What Does Linux Look Like?

One common misconception is that Linux is just a black screen full of cryptic commands. Modern desktop Linux looks polished, clean, and familiar. Here's what you'll find:

  • A full graphical desktop — taskbar, application launcher, file manager, notification area, just like Windows or macOS.
  • A web browser — Firefox comes pre-installed on most distros; Chrome and Edge are available to install.
  • An office suite — LibreOffice handles Word documents, Excel spreadsheets, and PowerPoint presentations with good compatibility.
  • A terminal — a text interface for running commands, available when you need it. Chapter 11 covers just enough to be capable.
  • An app store — most distros have a graphical software centre where you can browse and install applications with a click.
You can try Linux without installing anything. Every major distro can be run as a "live" session directly from a USB stick — your computer boots into a fully functional Linux desktop, you try it out, and when you shut down nothing has changed on your hard drive. This is how most people take their first look, and we cover it in Chapter 5.

Chapter Summary

ConceptWhat it means
Linux Strictly, the kernel (the core of the OS) created by Linus Torvalds in 1991. Commonly used to mean any complete Linux-based operating system.
Kernel The program that connects software to hardware. Always running in the background; users don't interact with it directly.
Open source The source code is publicly available — anyone can read, modify, and distribute it. Enables transparency, security auditing, and community development.
Distribution (distro) A complete, installable package of Linux: kernel + desktop + applications + package manager. Examples: Ubuntu, Fedora, Debian, Linux Mint.
Distro families Debian (apt), Red Hat/Fedora (dnf), Arch (pacman), SUSE (zypper). Distros in the same family share a package manager and many conventions.
Free software "Free as in speech" (freedom to use/modify/share) and usually "free as in beer" (no cost). Most desktop distros cost nothing to download and use.
Next: Chapter 2 — Choosing your distro. We look at the most popular options and match them to different use cases: best for beginners, development, servers, creative work, gaming, privacy, and older hardware.