Linux Command Line Basics

Introduction

• Linux command line tools are often used in terminal programs like Xterm.
• Commands in Linux are also applicable in Mac OS due to shared Unix heritage.
• Ubuntu is used here as the example Linux distribution.
• man command: Use man to access the manual page for detailed command syntax (e.g., man grep).

Basic Navigation and File Operations

• Terminal Access: Open via Applications > Terminal.
• List Directory Contents:
  • ls: Lists files and directories.
  • ls -l: Provides a detailed view including permissions and file sizes.
  • ls -l | more: Paginate long lists.
• Print Working Directory:
  • pwd: Shows the current directory path.
• Rename Files:
  • mv source destination: Renames or moves files.
  • Example: mv first.txt second.txt.
• Copy Files:
  • cp source destination: Copies files.
  • Example: cp second.txt third.txt.
• Remove Files:
  • rm file: Deletes files.

File Permissions

• Understanding Permissions:
  • Permissions are denoted by a string of characters (e.g., rw-r--r--).
  • r: Read, w: Write, x: Execute.
  • Permissions are set for User, Group, and Others.
• Change Permissions:
  • chmod: Change file permissions using numeric (e.g., 744) or symbolic notation (e.g., a-w).
• Change Ownership:
  • chown: Change file owner, requires sudo for elevated permissions.
  • Example: sudo chown new_owner file.

Working with Processes

• Process Management:
  • ps: View current processes.
  • ps -e | more: View all system processes with pagination.
  • Interactive Process Viewer:
    • top: Dynamic view of all processes; shows resource usage.
    • Quit with q.

Installing and Managing Software

• Package Management:
  • apt-get install package: Installs software on Debian-based systems.
  • yum: Similar function for Red Hat-based systems.
• Network Configuration:
  • ip address: View IP configuration.
  • Use sudo ip address add to modify IP settings.

Disk and Storage Management

• Disk Usage:
  • df: Displays disk space usage.
  • df -h: Human-readable format (e.g., GB, MB).

Searching and Finding Files

• Search:
  • grep pattern file: Search for text patterns.
• Find Files:
  • find . -name "*.txt": Find files by name from a starting directory.*

Network Tools

• Domain Resolution:
  • dig domain: Find IP addresses associated with a domain.

File Editing and Utilities

• Concatenate Files:
  • cat file1 file2 > both.txt: Concatenates files.
• Editing Files:
  • nano file: Full-screen text editor, supports basic operations like copy-paste.
  • Save in Nano with Ctrl-O and exit with Ctrl-X.

These commands and utilities form the foundation for managing Linux systems through the command line, offering tools for file management, process control, software installation, and system diagnostics.