basic OS commands

Focus: Terminal-first, step-by-step command explanations for practical exam prep Table of Contents Linux Basics & File System Linux Commands & Navigation File Permissions & Ownership Users & Groups Management SSH (Secure Shell) Apache Web Server Nginx Web Server Port Debugging & Troubleshooting Bash Scripting Docker Containers Lab Exercises Summary Quick Reference Cheat Sheet 1. Linux Basics & File System What is Linux? Linux is an open-source operating system kernel. A Linux Distribution (distro) is a collection of software built around the Linux kernel, all licensed under open-source or GPL. 90% of all cloud infrastructure is powered by Linux, making it the foundation of DevOps. Linux Distributions Debian-based: Ubuntu, Debian — use .deb packages and apt package manager Red Hat-based: CentOS, Fedora, RHEL — use .rpm packages and yum/dnf package manager Technical differences are mainly about packag