What is Linux?
You have probably heard the word “Linux” many times — maybe in the context of servers, Docker, cloud computing, or DevOps. But what actually is Linux?
Let’s clear that up once and for all.
Linux Is a Kernel, Not Just an Operating System
Here is a subtle but important distinction that trips up most beginners:
Linux is technically a kernel — the core software that sits between your hardware and your programs.
When people say “I use Linux”, they usually mean they use an operating system built around the Linux kernel. That full OS includes:
- The Linux kernel (hardware communication)
- GNU utilities (ls, cp, bash, grep — the tools you use daily)
- A package manager (apt, yum, pacman)
- Optionally, a desktop environment (GNOME, KDE, XFCE)
This combination is technically called a GNU/Linux system, though most people just say “Linux”.
Linux vs UNIX vs BSD
Linux was inspired by UNIX but is not UNIX. Here is how they relate:
| System | Origin | Kernel | Open Source? | Common Use |
|---|---|---|---|---|
| UNIX | AT&T Bell Labs, 1969 | Proprietary | No (originally) | Legacy enterprise systems |
| Linux | Linus Torvalds, 1991 | Linux kernel | Yes (GPL) | Servers, cloud, containers, Android |
| macOS | Apple, based on BSD | XNU (hybrid) | Partially | Apple devices |
| FreeBSD | Berkeley, derived from UNIX | BSD kernel | Yes | Networking, storage (Netflix uses it) |
The key point: Linux took ideas from UNIX (the design philosophy, the command structure) but was written from scratch. It is not UNIX — it is UNIX-like.
Linux Is Everywhere
Most people think of Linux as something for programmers and servers. The reality is much broader:
Where Linux runs today:
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✅ Web servers — Apache, Nginx on Linux
✅ Cloud compute — AWS EC2, GCP, Azure VMs default to Linux
✅ Android phones — Linux kernel under the hood
✅ Docker containers — all containers share a Linux kernel
✅ Kubernetes clusters — every node runs Linux
✅ Supercomputers — 100% of the Top500 run Linux
✅ Embedded systems — routers, TVs, cars, smart devices
✅ Your MacBook terminal — macOS is BSD-based (UNIX-like, not Linux)
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
Why Linux Dominates the Server World
Linux has over 90% market share on web servers. Here is why:
1. It is free. No per-server licensing fees like Windows Server.
2. It is stable. Linux servers routinely run for years without rebooting.
3. It is secure. Open-source code is audited by thousands of developers worldwide.
4. It is efficient. Linux runs well on minimal hardware — ideal for VMs and containers.
5. It is scriptable. Everything in Linux can be automated with shell scripts.
Major Linux Distributions
A distribution (or distro) is a packaged version of Linux with a specific kernel version, package manager, and default tools. Think of distros like different car models — same engine under the hood, different design and features.
| Distro | Based On | Package Manager | Best For |
|---|---|---|---|
| Ubuntu | Debian | apt | Beginners, cloud, general use |
| Debian | Itself | apt | Servers, stability-focused |
| CentOS Stream / Rocky Linux | RHEL | yum / dnf | Enterprise, RHCSA certification |
| Arch Linux | Itself | pacman | Advanced users, cutting-edge |
| Alpine Linux | Itself | apk | Docker containers (tiny: ~5MB) |
| Fedora | RHEL upstream | dnf | Developers, latest features |
For this tutorial series, we use Ubuntu 22.04 LTS — it is beginner-friendly, widely documented, and the default for most cloud environments.
Key Takeaways
- Linux is a kernel, not a complete OS on its own
- The full system is Linux kernel + GNU tools + package manager + optional GUI
- Linux is not UNIX but was heavily inspired by it
- Linux powers 90%+ of web servers, all Docker containers, and all major cloud platforms
- Different distros package Linux differently — Ubuntu is the best starting point for beginners
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