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Linux is a free and open-source operating system kernel first released by Linus Torvalds in 1991. Today, Linux powers everything from smartphones and embedded devices to the vast majority of the world's servers and cloud infrastructure.
The kernel is the core of the operating system. It manages:
The kernel alone is not a usable operating system — it needs user-space tools and applications.
The GNU Project provides the essential user-space tools:
Together, the Linux kernel and GNU tools form a complete operating system, often called GNU/Linux.
A distribution (distro) packages the kernel, GNU tools, a package manager, and additional software into a complete, installable operating system.
| Distribution | Base | Package Manager | Best For |
|---|---|---|---|
| Ubuntu | Debian | apt | Beginners, desktops, servers |
| Debian | Independent | apt | Stability, servers |
| Fedora | Independent | dnf | Developers, cutting-edge features |
| CentOS Stream / RHEL | Fedora | dnf / yum | Enterprise servers |
| Arch Linux | Independent | pacman | Advanced users, customisation |
| openSUSE | Independent | zypper | Enterprise, rolling release |
| Alpine Linux | Independent | apk | Containers, minimal footprint |
| Linux Mint | Ubuntu | apt | Desktop, Windows migrants |
Consider:
Linux is distributed under the GNU General Public License (GPL) version 2:
This licence model has enabled massive collaboration — the Linux kernel has over 15,000 contributors from thousands of organisations.
| Environment | Examples |
|---|---|
| Cloud servers | AWS EC2, Google Compute Engine, Azure VMs (90%+ run Linux) |
| Containers | Docker and Kubernetes run on Linux |
| Supercomputers | All of the world's top 500 supercomputers run Linux |
| Mobile | Android is based on the Linux kernel (3+ billion devices) |
| Embedded | Routers, smart TVs, IoT devices, car infotainment |
| Desktop | Ubuntu, Fedora, Linux Mint (growing market share) |
| Networking | Most network equipment runs Linux-based firmware |
┌──────────────────────────────┐
│ User Applications │
├──────────────────────────────┤
│ Shell (bash, zsh, fish) │
├──────────────────────────────┤
│ GNU Utilities / Libraries │
├──────────────────────────────┤
│ System Calls (open, read, │
│ write, fork, exec, socket) │
├──────────────────────────────┤
│ Linux Kernel │
│ ┌────────┬────────┬────────┐ │
│ │Process │ Memory │ File │ │
│ │ Mgmt │ Mgmt │Systems │ │
│ ├────────┼────────┼────────┤ │
│ │Network │ Device │Security│ │
│ │ Stack │Drivers │Modules │ │
│ └────────┴────────┴────────┘ │
├──────────────────────────────┤
│ Hardware │
└──────────────────────────────┘
To follow along with this course, you can use Linux in several ways:
| Method | Description |
|---|---|
| Virtual machine | Install Ubuntu or Fedora in VirtualBox or VMware |
| WSL 2 | Windows Subsystem for Linux (runs natively on Windows) |
| Cloud instance | Launch a free-tier VM on any cloud provider |
| Live USB | Boot Linux from a USB drive without installing |
| Dual boot | Install Linux alongside your existing OS |
Tip: For beginners, Ubuntu on WSL 2 or a virtual machine is the easiest way to start.
Linux is a free, open-source operating system kernel that, combined with GNU tools and a distribution, forms a complete OS. It dominates servers, cloud infrastructure, supercomputers, and mobile devices. Understanding Linux is an essential skill for developers, system administrators, and anyone working in DevOps. In the following lessons, we will learn to navigate the filesystem, manage files, and master the command line.