Linux Basics

Linux Overview

Linux is a powerful, open-source operating system (OS) kernel that, when combined with other software, forms complete OSes called distributions (distros), known for being free, secure, stable, and highly customizable, powering everything from servers, supercomputers, and Android devices to personal desktops, offering unparalleled control and flexibility for developers, businesses, and general users.

Filesystem Structure

Understanding the Linux filesystem hierarchy is essential for navigating and managing resources effectively.

• / – Root directory
• /home – User home directories
• /etc – Configuration files
• /var – Variable data like logs
• /usr – User applications and binaries

Basic Linux Commands

Essential commands every DevOps engineer should know:

• ls – List directory contents
• cd – Change directory
• pwd – Show current directory
• cp – Copy files and directories
• mv – Move or rename files
• rm – Remove files or directories
• mkdir – Create directories
• cat, less, head, tail – View file contents

User and Group Management

Managing users and groups is critical for permissions and security:

• useradd, usermod, userdel – Manage users
• groupadd, groupmod, groupdel – Manage groups
• passwd – Set user passwords
• Checking users: id, who, groups

Permissions Basics

Linux uses read, write, and execute permissions to control access:

• chmod – Change file/directory permissions
• chown – Change owner and group
• ls -l – View permissions and ownership
• sudo – Execute commands with superuser privileges

Package Management Overview

Install, update, and remove software using package managers:

• apt (Debian/Ubuntu)
• yum (RHEL/CentOS 7)
• dnf (Fedora/RHEL 8+)
• Update system packages regularly for security