What is Linux?
What is an Operating System?
Before we talk about Linux, we need to understand what an Operating System (OS) really is — because Linux is an operating system.
An operating system is the core software that manages all of a computer's hardware and provides a platform for other programs to run. Without it, your CPU, RAM, and hard drive are just expensive pieces of metal with no idea what to do.
Think of the OS as the manager of a busy restaurant. The kitchen (hardware) can cook, but the manager decides which orders (apps) get cooked first, which chef (CPU core) handles what, how much freezer space (RAM) each dish prep gets, and who is allowed in the kitchen (security). Without the manager, it's chaos.
What Does an Operating System Do?
- Process Management - Runs multiple programs at the same time (multitasking). Decides which program gets CPU time and for how long.
- Memory Management - Allocates RAM to running programs and frees it when they close.
- File System Management - Organizes data as files and folders on your disk (HDD/SSD).
- Device Drivers - Acts as a translator between the OS and hardware (keyboard, mouse, GPU, printer).
- Security & Access Control - Controls which users and programs can access which resources.
- User Interface - Provides a way to interact: either a GUI (graphical) or CLI (command line).
- Networking - Manages internet connections, protocols, and data transfer.
OS Architecture - The Big Picture
Popular Operating Systems Today
| Operating System | Developer | Common Use | Cost | Open Source? |
|---|---|---|---|---|
| Windows 11 | Microsoft | Desktop, Gaming | Paid (~$139) | No |
| macOS Sequoia | Apple | Creative work, Mac hardware | Free (Mac only) | No |
| Ubuntu Linux | Canonical | Desktop, Server, Dev | Free | Yes |
| Android | Smartphones, Tablets | Free | Partially | |
| iOS / iPadOS | Apple | iPhone, iPad | Free (Apple only) | No |
| Chrome OS | Chromebooks | Free | Partially |
Android — the OS on over 3 billion smartphones — runs on the Linux kernel. So chances are you've been using Linux your whole life without knowing it!
What is Linux?
Linux is a free, open-source operating system kernel created by Linus Torvalds in 1991. A "kernel" is the innermost core of an OS — the part that directly talks to hardware.
When people say "Linux" in everyday conversation, they usually mean a full operating system built around the Linux kernel (kernel + shell + utilities + desktop environment). Technically this is called GNU/Linux, but "Linux" is the common shorthand.
The kernel is just one component (the engine). The full OS includes the kernel + shell (command interpreter) + system utilities + desktop environment. Linux provides the engine; distributions (Ubuntu, Fedora, etc.) build the full car around it.
Why Should You Learn Linux?
- ✅ 100% Free — No license costs ever. Install on as many machines as you want.
- ✅ Open Source — Anyone can read, modify, and distribute the source code.
- ✅ Highly Secure — Far fewer viruses and malware than Windows. Used in banking, hospitals, military.
- ✅ Rock-Solid Stability — Linux servers routinely run for years without rebooting.
- ✅ Runs on Old Hardware — A 10-year-old laptop can run Linux Mint smoothly.
- ✅ Powers the Internet — 96% of web servers, all supercomputers, most cloud infrastructure runs Linux.
- ✅ Developer's Best Friend — Native support for Python, Node, Docker, Git, databases without fuss.
- ✅ Privacy Focused — No telemetry, no hidden data collection by default.
- ✅ Career Advantage — DevOps, Cloud, Cybersecurity, Backend Dev — Linux knowledge is essential.
Linux vs Windows vs macOS
| Feature | Linux | Windows | macOS |
|---|---|---|---|
| Cost | Free | ~$139 | Free (Mac hardware required) |
| Open Source | ✅ Yes | ❌ No | ❌ No |
| Security | ⭐⭐⭐⭐⭐ | ⭐⭐⭐ | ⭐⭐⭐⭐ |
| Stability | ⭐⭐⭐⭐⭐ | ⭐⭐⭐ | ⭐⭐⭐⭐ |
| Customisability | ⭐⭐⭐⭐⭐ | ⭐⭐ | ⭐⭐ |
| Gaming | ⭐⭐⭐ | ⭐⭐⭐⭐⭐ | ⭐⭐ |
| Software Compatibility | ⭐⭐⭐ | ⭐⭐⭐⭐⭐ | ⭐⭐⭐⭐ |
| Server Use | ⭐⭐⭐⭐⭐ | ⭐⭐⭐ | ⭐⭐ |
| Dev / Programming | ⭐⭐⭐⭐⭐ | ⭐⭐⭐ | ⭐⭐⭐⭐ |
Linux History
The Story Begins — UNIX (1969)
To understand Linux, you need to go back to 1969 at Bell Labs (AT&T), where Ken Thompson and Dennis Ritchie created UNIX — a powerful, multi-user, multitasking OS written in C. UNIX became the gold standard of operating systems, but it was commercial and expensive.
The GNU Project (1983)
In 1983, Richard Stallman at MIT launched the GNU Project with a bold goal: create a completely free UNIX-like operating system. GNU stands for "GNU's Not Unix" (a programmer's recursive joke). By 1990, GNU had developed most of the tools needed for a complete OS — compilers, shell, text editors — but was missing the most important piece: the kernel.
Linus Torvalds Creates the Linux Kernel (1991)
In 1991, a 21-year-old Finnish computer science student named Linus Torvalds was frustrated with the licensing restrictions of MINIX (a small teaching OS). He decided to write his own kernel — just as a hobby.
"I'm doing a (free) operating system (just a hobby, won't be big and professional like GNU) for 386(486) AT clones." — Linus Torvalds, 1991 Usenet post
He had no idea he was about to change the world. The first version, Linux 0.01, contained just 10,239 lines of code.
Linux Timeline
1969 ──▶ UNIX created at Bell Labs (Ken Thompson & Dennis Ritchie)
Multi-user, multitasking OS written in C
1983 ──▶ Richard Stallman launches GNU Project
Goal: free, open-source UNIX replacement
Provides: GCC compiler, bash shell, GNU utilities
1991 ──▶ Linus Torvalds (age 21) writes Linux kernel v0.01
Posts to Usenet: "just a hobby" project
10,239 lines of code
1992 ──▶ Linux kernel licensed under GNU GPL v2
GNU tools + Linux kernel = complete free OS (GNU/Linux)
First distributions appear
1993 ──▶ Slackware — first major Linux distribution
Debian — community-driven, still hugely popular today
1994 ──▶ Linux kernel v1.0 released (176,250 lines of code)
Red Hat Linux founded
1996 ──▶ Tux the penguin adopted as Linux mascot
(Linus liked penguins after being bitten by one in Australia)
1998 ──▶ IBM, Intel, Oracle begin contributing to Linux
"Halloween Documents" — Microsoft internally calls Linux a threat
2003 ──▶ Linux kernel v2.6 — major improvements for enterprise use
2004 ──▶ Ubuntu 4.10 released — Linux for everyone
Made Linux accessible to ordinary users
2007 ──▶ Android announced (uses Linux kernel)
Linux enters the mobile world
2008 ──▶ Android officially launched on first smartphone
2011 ──▶ Linux turns 20 — powers 91% of top 500 supercomputers
2019 ──▶ Microsoft (!) joins the Linux Foundation
WSL2 brings Linux to Windows natively
2022 ──▶ Linux kernel v6.0 — 36+ million lines of code
3,000+ developers contribute from 200+ companies
Today ──▶ 96% of web servers, 100% of top 500 supercomputers,
3+ billion Android devices — all running Linux
The International Space Station switched from Windows to Linux in 2013 for greater reliability and security. Linux is literally running in space!
Linux Distributions (Distros)
The Linux kernel alone is not a usable OS — you can't interact with just a kernel. A Linux distribution (distro) takes the kernel and bundles it with a package manager, desktop environment, pre-installed apps, and tools to create a complete, usable OS.
The Linux kernel is like a car engine. Different manufacturers (Debian, Red Hat, Arch) take that same engine and build completely different cars around it — different exteriors, dashboards, features, and target audiences — but the same core engine inside.
The Distribution Family Tree
LINUX KERNEL
│
┌──────────────────┼──────────────────┐
│ │ │
DEBIAN RED HAT ARCH
(community) (enterprise) (rolling)
│ │ │
┌──────┼──────┐ ┌──────┼──────┐ ┌─────┼─────┐
│ │ │ │ │ │ │ │ │
Ubuntu Mint Kali RHEL CentOS Fedora Arch Manjaro EndeavourOS
│ (upstream)
├──────────────────┐
│ │ │
Pop!_OS Lubuntu Xubuntu
(LXDE) (XFCE)Popular Linux Distributions Compared
| Distribution | Based On | Best For | Difficulty | Package Manager | Desktop |
|---|---|---|---|---|---|
| Ubuntu 24.04 LTS | Debian | Beginners, Developers | ⭐ Easy | apt | GNOME |
| Linux Mint 21 | Ubuntu | Windows switchers | ⭐ Very Easy | apt | Cinnamon |
| Pop!_OS | Ubuntu | Developers, NVIDIA GPU | ⭐ Easy | apt | GNOME |
| Fedora 40 | Red Hat | Developers, cutting-edge | ⭐⭐ Medium | dnf | GNOME |
| Debian 12 | Independent | Servers, stability | ⭐⭐ Medium | apt | GNOME/XFCE |
| openSUSE | Independent | Enterprise desktop | ⭐⭐ Medium | zypper | KDE Plasma |
| Arch Linux | Independent | Advanced users, DIY | ⭐⭐⭐⭐ Hard | pacman | Any (manual) |
| Manjaro | Arch | Arch benefits, easier setup | ⭐⭐ Medium | pacman | KDE/XFCE |
| Kali Linux | Debian | Cybersecurity, pen testing | ⭐⭐⭐ Advanced | apt | XFCE |
| AlmaLinux / Rocky | Red Hat | Enterprise servers | ⭐⭐ Medium | dnf | GNOME |
We will use Ubuntu 24.04 LTS throughout this course. It has the best community support, excellent hardware compatibility, and the most beginner-friendly experience. LTS (Long-Term Support) means it receives updates for 5 years.
Desktop Environments - What You Actually See
| Desktop Environment | Look & Feel | RAM Usage | Best For | Default In |
|---|---|---|---|---|
| GNOME | Modern, minimal, iOS-like | ~700 MB | Modern workflow | Ubuntu, Fedora |
| KDE Plasma | Feature-rich, Windows-like | ~500 MB | Power users, customisation | Kubuntu, Manjaro KDE |
| Cinnamon | Polished, Windows-like | ~450 MB | Windows switchers | Linux Mint |
| XFCE | Lightweight, traditional | ~250 MB | Older hardware | Xubuntu, Kali |
| LXQt / LXDE | Ultra-lightweight | ~150 MB | Very old or weak hardware | Lubuntu |
| MATE | Classic GNOME 2 style | ~300 MB | Traditional workflow | Ubuntu MATE |
People often confuse these two. Kubuntu is Ubuntu (distro) with KDE Plasma (DE). Xubuntu is Ubuntu (distro) with XFCE (DE). Same core OS, different visual interface and default apps. You can also install multiple DEs on one system.
Quick Recap
- An OS manages hardware and runs your programs
- Linux is a free, open-source OS kernel created by Linus Torvalds in 1991
- Linux powers servers, Android phones, supercomputers, and the cloud
- A distro = Linux kernel + desktop environment + package manager + apps
- For beginners: start with Ubuntu 24.04 LTS or Linux Mint
Next UpIn the next lesson, you'll learn how to safely run Linux inside your current Windows PC using VirtualBox — without touching your existing files or partitions.
In the next lesson, you'll learn how to safely run Linux inside your current Windows PC using VirtualBox — without touching your existing files or partitions.
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