Linux Commands Every Hacker Must Know — Cheat Sheet 2025

Linux Commands Every Hacker Needs

Linux is the operating system of hackers. Whether you're using Kali Linux, Ubuntu, or Parrot OS, mastering these commands will make you significantly more effective as a security professional.

File System Navigation

pwd             # Print current working directory
ls -la          # List files with permissions and hidden files
ls -lah         # Same but human-readable file sizes
cd /path        # Change directory
cd ..           # Go up one directory
cd ~            # Go to home directory
cd -            # Go to previous directory

# Find files
find / -name "*.txt" 2>/dev/null
find / -perm -4000 2>/dev/null    # Find SUID files (privilege escalation)
find /home -name "*.conf"         # Find config files
locate filename                   # Fast search (uses database)

File Operations

cat file.txt              # Display file contents
head -n 20 file.txt       # First 20 lines
tail -n 20 file.txt       # Last 20 lines
tail -f /var/log/auth.log # Watch file in real-time
less file.txt             # Page through file

# Copy, move, delete
cp source dest            # Copy
cp -r dir/ /backup/       # Copy directory recursively
mv file.txt /tmp/         # Move/rename
rm file.txt               # Delete file
rm -rf directory/         # Delete directory (CAREFUL!)

# Text manipulation
grep "pattern" file.txt                    # Search for pattern
grep -r "password" /var/www/               # Recursive search
grep -i "error" log.txt                    # Case insensitive
cat /etc/passwd | grep -v "nologin"        # Filter out nologin accounts
awk -F: '{print $1}' /etc/passwd           # Extract usernames
cut -d: -f1,3 /etc/passwd                  # Cut specific fields

Network Commands

# IP and interfaces
ip a                            # Show all interfaces and IP addresses
ip route                        # Show routing table
ifconfig                        # Traditional interface info

# Connectivity
ping 8.8.8.8                    # Test connectivity
ping -c 4 google.com            # Send 4 pings only
traceroute google.com           # Trace route to host
mtr google.com                  # Combined ping + traceroute

# DNS
nslookup example.com            # Basic DNS lookup
dig example.com                 # Detailed DNS info
dig example.com MX              # Mail server records
dig @8.8.8.8 example.com        # Use specific DNS server
host example.com                # Simple DNS lookup

# Open connections
netstat -tulpn                  # Show listening ports with PID
ss -tulpn                       # Modern alternative to netstat
lsof -i :80                     # Who is using port 80?
lsof -i :443

Process Management

ps aux                          # All running processes
ps aux | grep apache            # Find specific process
top                             # Real-time process monitor
htop                            # Better top (colored)
kill 1234                       # Kill process by PID
kill -9 1234                    # Force kill
killall nginx                   # Kill by name
pkill -f "python script.py"     # Kill by command pattern

# Background jobs
command &                       # Run in background
jobs                            # List background jobs
fg 1                            # Bring job 1 to foreground
bg 1                            # Continue job 1 in background
nohup command &                 # Run immune to hangup

User and Permission Management

whoami                          # Current user
id                              # User ID, group memberships
sudo command                    # Run as root
sudo -l                         # List sudo permissions
su username                     # Switch user

# File permissions
chmod 755 script.sh             # rwxr-xr-x
chmod +x script.sh              # Add execute permission
chmod 600 private_key.pem       # rw------- (SSH key)
chown user:group file.txt       # Change owner
chown -R www-data /var/www/     # Recursive ownership change

# SUID/SGID (important for privilege escalation)
find / -perm -u=s 2>/dev/null   # Find SUID files
find / -perm -g=s 2>/dev/null   # Find SGID files

Services and Ports

# Service management (systemd)
sudo systemctl start apache2
sudo systemctl stop apache2
sudo systemctl restart apache2
sudo systemctl status apache2
sudo systemctl enable apache2   # Start on boot

# Traditional init.d
sudo service ssh start
sudo service ssh status

# Check all listening ports
sudo nmap -sS localhost
sudo netstat -tlnp

Compression and Archives

# tar archives
tar -czf archive.tar.gz directory/    # Create compressed archive
tar -xzf archive.tar.gz               # Extract archive
tar -tzf archive.tar.gz               # List contents

# zip
zip -r archive.zip directory/
unzip archive.zip -d /destination/

SSH Operations

# Connect to remote host
ssh user@192.168.1.1
ssh -p 2222 user@host.com              # Custom port
ssh -i key.pem user@host.com          # Using private key

# Copy files securely
scp file.txt user@192.168.1.1:/tmp/    # Upload
scp user@192.168.1.1:/tmp/file.txt .   # Download
scp -r directory/ user@host:/backup/   # Copy directory

# SSH tunneling (port forwarding)
ssh -L 8080:localhost:80 user@server   # Local port forward
ssh -R 4444:localhost:4444 user@server # Remote port forward

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