Linux Command Line Reference Guide

File System Operations

Navigation

pwd                    # Print working directory cd /path/to/dir        # Change directory cd ~                   # Go to home directory cd -                   # Go to previous directory cd ..                  # Go up one level

Listing Files

ls                     # List files ls -l                  # Long format ls -a                  # Show hidden files ls -lh                 # Human-readable sizes ls -lt                 # Sort by time

File Operations

cp file1 file2          # Copy file cp -r dir1 dir2        # Copy directory mv file1 file2         # Move/rename rm file                # Remove file rm -rf dir             # Remove directory (careful!) mkdir dir              # Create directory rmdir dir              # Remove empty directory touch file             # Create empty file

Viewing Files

cat file                # Display file content less file              # Page through file head file              # First 10 lines tail file              # Last 10 lines tail -f file           # Follow file (logs)

File Permissions

chmod 755 file          # Set permissions chmod +x file          # Make executable chown user:group file  # Change ownership chgrp group file       # Change group ls -l                  # View permissions

Process Management

ps                     # List processes ps aux                 # Detailed process list top                    # Interactive process viewer htop                   # Enhanced top (if installed) kill PID               # Kill process killall process        # Kill all instances jobs                   # List background jobs fg %1                  # Bring job to foreground bg %1                  # Send job to background

System Information

uname -a               # System information hostname               # Hostname uptime                 # System uptime free -h                # Memory usage df -h                  # Disk space du -sh dir             # Directory size lscpu                  # CPU information

Network Commands

ip addr show           # Show IP addresses ip route show          # Show routing table ping host              # Test connectivity curl url               # Download/request wget url               # Download file netstat -tulpn         # Network connections ss -tulpn              # Modern netstat

Package Management

Debian/Ubuntu (apt)

apt update              # Update package list apt upgrade            # Upgrade packages apt install package    # Install package apt remove package     # Remove package apt search keyword     # Search packages apt list --installed   # List installed

Red Hat/CentOS (yum/dnf)

yum update              # Update packages yum install package    # Install package yum remove package     # Remove package yum search keyword     # Search packages

Text Processing

grep pattern file       # Search text
grep -r pattern dir    # Recursive search
sed 's/old/new/g' file  # Replace text
awk '{print $1}' file   # Process columns
sort file              # Sort lines
uniq file              # Remove duplicates
wc -l file             # Count lines

Compression

tar -czf archive.tar.gz dir    # Create tar.gz tar -xzf archive.tar.gz       # Extract tar.gz zip -r archive.zip dir        # Create zip unzip archive.zip              # Extract zip gzip file                     # Compress file gunzip file.gz                # Decompress

Useful Shortcuts

Ctrl+C                  # Cancel command Ctrl+D                  # Exit shell Ctrl+L                  # Clear screen Ctrl+R                  # Search history !!                      # Repeat last command !n                      # Execute command n from history