Linux Basics for Hackers - Cheat Sheet

A comprehensive Linux cheat sheet for hackers and security professionals, covering essential commands for navigation, permissions, networking, reconnaissance, system monitoring, and hacking tools — with runnable examples.

Linux is the go-to operating system for hackers and security professionals. Whether you're diving into ethical hacking, penetration testing, or cybersecurity research, mastering Linux is a must. This cheat sheet will help you get started with essential Linux commands and concepts every hacker should know — each with a practical example you can run yourself.

Why Linux for Hackers?

Open-source & customizable — full control over the OS
Powerful command-line tools — hundreds of built-in utilities
Preferred by cybersecurity experts — Kali, Parrot, and BlackArch are built on it
Widely used in penetration testing — from recon to post-exploitation

Basic Linux Commands

The bread and butter of navigating any Linux system.

# Print the current working directory
pwd
 
# List files and directories (add -l for details, -a for hidden files)
ls
ls -la
 
# Change directory
cd /var/log
cd ..          # go up one level
cd ~           # go to your home directory
 
# Create a directory
mkdir myfolder
mkdir -p a/b/c # create nested directories
 
# Remove a file or directory (be careful! no undo)
rm file.txt
rm -rf myfolder
 
# Copy files and directories
cp file.txt copy.txt
cp -r folder backup_folder
 
# Move or rename files
mv file.txt new_name.txt
mv new_name.txt /tmp/
 
# Display file contents
cat /etc/passwd
 
# Open a file in an editor
nano notes.txt
vim notes.txt
 
# Show command history
history
history | tail -20
 
# Clear the terminal
clear

User & Permission Commands

Control who you are and who can touch your files.

# Show current user
whoami
 
# Display user ID and group ID
id
id root
 
# Execute a command as root
sudo apt update
sudo whoami   # shows 'root' when run with sudo
 
# Change file permissions
# r=read(4) w=write(2) x=execute(1)
chmod 755 script.sh
chmod +x script.sh        # make executable
chmod 600 secret.key      # owner read/write only
 
# Change file owner
chown root:root file.txt
chown -R www-data:www-data /var/www
 
# Change user password
passwd
sudo passwd root

Networking & Reconnaissance

Gather information about networks, hosts, and services.

# Show network interfaces and IP addresses
ifconfig
ip a
 
# Check network connectivity to a host
ping google.com
ping -c 4 8.8.8.8     # send exactly 4 packets
 
# Display active network connections and listening ports
netstat -tulpn
ss -tulpn             # modern replacement for netstat
 
# Scan network ports
nmap -sV 192.168.1.1
nmap -sC -sV -p- 10.0.0.5
 
# Fetch data from a URL
curl https://example.com
curl -o page.html https://example.com
wget https://example.com/file.zip
 
# DNS lookup
dig example.com
nslookup example.com

Process & System Monitoring

See what's running on the box and keep an eye on resources.

# Show running processes
ps aux
ps aux | grep nginx
 
# Display system processes in real time
top
htop        # interactive, nicer view
 
# Terminate a process (find PID first)
ps aux | grep nc
kill 1234                 # kill by PID
kill -9 1234              # force kill
 
# Show disk space usage (human readable)
df -h
 
# Show memory usage in megabytes
free -m
 
# Check system uptime and load average
uptime
 
# Display system and kernel info
uname -a
 
# Show who is logged in
who

Locate files and manipulate archives.

# Find files and directories by name
find / -name "config.yml"
find /home -type f -name "*.conf"
 
# Search text within files
grep "root" /etc/passwd
grep -r "password" /etc/
 
# Compress/extract tar archives
tar -czvf archive.tar.gz folder/     # compress
tar -xzvf archive.tar.gz             # extract
 
# Create/extract ZIP files
zip -r files.zip folder/
unzip files.zip -d output/
 
# Find files quickly (uses a database)
sudo updatedb
locate sshd_config

Essential Hacking Tools in Linux

Tools you'll reach for constantly during a pentest.

Tool	Purpose	Example usage
`nmap`	Network scanning	`nmap -sS 192.168.1.0/24`
`Metasploit`	Exploitation framework	`msfconsole`
`Wireshark`	Packet analysis	`wireshark`
`Hydra`	Brute-force attacks	`hydra -l admin -P pass.txt ssh://192.168.1.1`
`John the Ripper`	Password cracking	`john hash.txt`
`sqlmap`	SQL injection testing	`sqlmap -u "http://target/page?id=1"`
`aircrack-ng`	Wi-Fi penetration testing	`aircrack-ng -w wordlist.txt capture.cap`

Final Thoughts

This cheat sheet gives you a solid foundation in Linux, essential for cybersecurity and ethical hacking. Keep practicing these commands, explore more tools, and stay updated with new techniques.

Try it yourself: spin up a Kali Linux VM (or any distro) and run through each example above. The best way to learn Linux is by breaking things — in a sandbox, of course.

Happy Hacking!