What is Linux?
Linux is the foundational operating system of the cloud and modern infrastructure. From web servers and containers to supercomputers and Android devices, mastering Linux is the first step in any DevOps engineer's journey.
The Linux operating system is a complete, open source operating system that combines the GNU utilities and the Linux kernel. The kernel is the central core of the Linux operating system. It manages all the computer's physical devices. The term kernel is generally used to describe the main part of any operating system.
The Linux kernel was developed by Linus Torvalds in 1991, while he was a student at the University of Helsinki. He developed a UNIX-like operating system kernel for his own use. He posted his creation on the Internet and asked other programmers to help him further develop it. Until Torvalds agreed to release Linux under GPL, the GNU project was not a complete operating system. And the kernel itself was incomplete as an operating system without utilities.
Over the past few years, Linux has rapidly gained ground in the competitive operating system marketplace. For example, Linux is now widely preferred for web servers and Internet systems. Many individuals and organizations have accepted it as a desktop and server alternative because of its high security, low cost, and ease of licensing.
Linux is used on servers, workstations, and desktops. Servers are computers optimized for supplying services to other computers. Workstations are computers optimized for use by business users. Desktops are used primarily by home users and small businesses.
Mental model: Everything in Linux is a file or a process. The OS acts as the bridge between user applications and the physical hardware.
Architecture
Userland, shell, system calls, and the kernel. Understanding these layers demystifies how Linux works.
Command Line
The shell is your primary tool. Mastering navigation, text processing, and system commands is essential.
Permissions & Users
Security is built-in. Owners, groups, and rwx flags control exactly who can access what on the system.
Core Linux Concepts
The fundamental building blocks of every Linux system.
The Kernel
The kernel is the brain of Linux — it controls hardware and makes it interact with applications. It manages the CPU, memory, devices, and all running programs. The latest kernel is always available at kernel.org.
Distributions (Distros)
A distro bundles the kernel, tools, utilities, libraries, and a desktop environment into a complete installable OS.
Boot Loaders
A boot loader is a program that loads the kernel so that Linux and other operating systems can boot. During installation, it is put on the Master Boot Record (MBR). GRand Unified Bootloader (GRUB) is the standard Linux boot loader. See the Boot Process Guide for details.
Services (Daemons)
Programs that run as background processes, started at boot.
Filesystems
Methods for organising files on disk. The X Window System provides the GUI protocol layer.
Desktop & Shell (Terminal)
The desktop is the graphical UI. A command line interpreter, often called a command line shell, is a program that interprets commands. It analyzes the input provided by the user, interprets the text in context, and supplies the output. The terms shell, command line, and terminal are frequently used interchangeably to describe this environment.
Start here — pick a topic
Each guide provides hands-on commands, explanations, and visual models.
File System
The single-root hierarchy, FHS structure, and where to find binaries, configs, and logs.
/etc • /var • /usr • /proc
Commands
Essential bash commands for navigation, file manipulation, and text processing.
grep • awk • sed • find
Permissions
Understanding read/write/execute, owners, groups, octal notation, and special bits.
chmod • chown • 755 • SUID
Boot Process
From power button to login prompt — BIOS, GRUB, kernel, initramfs, and init explained interactively.
BIOS • GRUB • Kernel • initramfs • PID 1
Processes & Networking
Managing system states, background jobs, IP addresses, ports, and troubleshooting connectivity.
ps • kill • ip • ss
Package Management
Master APT to securely download, install, update, and remove software on Debian-based systems.
apt update • install • purge
Logging & Monitoring
Syslogd, rsyslog, journalctl, and log rotation for system maintenance.