DESCRIPTION
You use Linux every day — even if you don’t realize it. The websites you visit, the banks that hold your money, streaming services, Android smartphones — all of this runs on Linux. As of 2026, over 80% of public web servers worldwide run on Linux. In cloud infrastructure — AWS, Google Cloud, Azure — that number exceeds 96%. If you want to secure servers, you need to understand exactly what you are protecting and why this system is built the way it is.
WHAT YOU WILL LEARN
What Linux is and how it differs from Windows and macOS
Why Linux dominates servers worldwide
What distributions exist and which one to choose for a server
Why Linux is considered a more secure system
Where to start your journey into Linux security
WHAT IS LINUX
Linux is an open-source operating system. Anyone can see how it works, find bugs, and propose fixes. Thousands of developers around the world continuously improve the system — this makes Linux a reliable and secure foundation for servers.
If Windows is a closed box where the manufacturer decides what goes inside, then Linux is a construction kit that you can disassemble down to the last bolt and rebuild to suit your needs.
In 1991, Finnish student Linus Torvalds wrote the first version of the Linux kernel out of pure curiosity. Today, thousands of engineers from Google, Intel, Red Hat, Meta, and other companies contribute to the kernel. What started as a student project became the foundation of the modern internet.
WHY LINUX ON SERVERS
Linux did not dominate servers by accident. The reasons are straightforward and practical:
Stability. Linux servers run for years without rebooting. Updates can be applied without stopping the system.
Security. Open source means vulnerabilities are found and fixed quickly. The permission architecture was designed from the ground up for multi-user environments.
Cost. Most server Linux distributions are free. You only pay for support if you need it.
Flexibility. You can configure the system precisely for the task — remove everything unnecessary, keep only what is needed. Less code means fewer vulnerabilities.
Performance. Linux uses server resources efficiently. The same hardware running Linux handles greater load than it would running Windows Server.
LINUX DISTRIBUTIONS
Linux is the kernel of the system. Different teams and companies build their own distributions around it — complete operating systems with a set of programs and tools.
The most commonly used server distributions:
Ubuntu Server — the most popular choice for beginners and startups. Large community, extensive documentation, packages are always up to date. LTS versions are supported for 5 years. Current LTS versions as of 2026 are Ubuntu 24.04 and Ubuntu 26.04 (released April 2026).
Debian — stability above all else. Packages go through a long review process before being included in a release. Ideal for production servers where reliability matters more than novelty.
CentOS Stream / Rocky Linux / AlmaLinux — compatible with Red Hat Enterprise Linux (RHEL). Popular in enterprise environments. Rocky Linux and AlmaLinux emerged as replacements for CentOS after Red Hat changed its policy in 2021.
RHEL (Red Hat Enterprise Linux) — the enterprise standard with paid support. Used by banks, government agencies, and large businesses.
For this course, Ubuntu Server 24.04 LTS or Debian 12 will work well. All commands and examples have been tested on these systems.
LINUX AND SECURITY
Linux is not a magically secure system. A poorly configured Linux server gets compromised just as easily as any other. The difference is that Linux provides the tools for proper configuration — and that is exactly what this course is about.
A few facts that are important to understand from the very beginning:
Root is not just an administrator. It is absolute power over the system. Working as root constantly is like walking around with a loaded weapon and no safety on.
Linux permissions are granular. You can precisely specify who can do what with every file and process.
Most breaches happen not through kernel vulnerabilities, but through configuration errors, weak passwords, and outdated software. This means proper configuration is your primary defense.
PRACTICE
Check which operating system is installed on your server:
uname -aView the distribution version:
cat /etc/os-releaseFind out how long the server has been running without a reboot:
uptimeSee how many users are currently logged into the system:
whoCOMMON MISTAKES
Working as root all the time. This is a dangerous habit — one wrong command can destroy the system. Always work as a regular user and use sudo only when necessary.
Installing everything indiscriminately. Every installed package is a potential vulnerability. Install only what you actually need.
Ignoring updates. Most breaches exploit known vulnerabilities that already have patches available. Update your system regularly.
IMPORTANT TO KNOW
Linux is the kernel, not a complete OS. What we casually call “Linux” is actually a distribution — the kernel plus a set of programs and tools.
Android also runs on the Linux kernel — but that does not mean server Linux skills apply directly to Android. They are different ecosystems.
Server Linux runs without a graphical interface. All work is done through the command line — this is not an inconvenience, it is an advantage. Less code, fewer vulnerabilities, lower resource consumption.
CHECK YOURSELF
1. What percentage of public web servers run on Linux as of 2026?
2. What is the difference between a Linux distribution and the Linux kernel?
3. Name three reasons why Linux dominates on servers.
4. Why is working constantly as root considered a dangerous practice?
5. Which Linux distribution is recommended for beginners and why?
CONCLUSIONS
Linux is the foundation of modern server infrastructure. Understanding its history and architecture helps you approach security with intention. Open source code, granular permissions, and configuration flexibility make Linux a powerful tool in the hands of a knowledgeable administrator — and a dangerous hole in the hands of an inexperienced one. The difference between these two scenarios is knowledge and good habits. That is exactly what we will be building throughout this course.