linux
Debian Linux Commands
Debian-Bassed Linux Command Cheat Sheet & Reference 🛠️
This document serves as a quick reference for common system administration, networking, and security auditing commands on Debian/Ubuntu-based systems.
1. SSH and File Permissions
| Command | Purpose | Explanation |
|---|---|---|
ssh-keygen -R 192.168.0.1 |
Remove SSH Key | Removes the host key for the specified IP from your known_hosts file. Use this if the remote server key changes. |
sudo chmod u+x my_script.sh |
Allow Execution | Adds the execute permission (+x) for the user (u+) who owns the file, making a script runnable. |
sudo chmod 644 |
File Permissions | Owner can read/write; Group/Others can only read (standard file permission). |
sudo chmod 755 |
Script/Directory Permissions | Owner can read/write/execute; Group/Others can read/execute (standard directory/script permission). |
2. Package Management (apt) Repairs
| Command | Purpose | Explanation |
|---|---|---|
sudo apt --fix-broken install |
Fix Broken Dependencies | Attempts to correct a system where packages have unmet dependencies. |
sudo apt remove [package_name] |
Remove Package | Basic command to uninstall a specified package (requires a package name). |
3. Diagnostics and System Info
| Command | Purpose | Explanation |
|---|---|---|
ls -la /usr/folder1/folder2/ |
Check Files/Folders | Lists all (-a) files in the path with long format details (-l). |
lsblk |
List Disks | Lists all block devices (drives and partitions) on the system. |
free -h |
Memory Usage | Displays free, used, and total system memory and swap space in a human-readable format. |
sudo iftop |
Network Traffic (General) | Displays network bandwidth usage on an interface in real-time. |
sudo nethogs |
Network Traffic (Per Process) | Displays which process/program is using the most network bandwidth. |
ncdu |
Disk Usage | An interactive ncurses utility for visualizing disk space usage. |
htop |
Process Viewer | An interactive, improved version of the top command for monitoring processes and resources. |
btop |
Modern Monitor | A feature-rich, visually appealing resource monitor. |
4. Storage and File System Management
| Command | Purpose | Explanation |
|---|---|---|
sudo mount -t exfat /dev/sdXN /mnt/your_mount_point |
Mount ExFAT Drive | Mounts an ExFAT-formatted drive to the specified mount point. Replace sdXN with actual device (e.g., sdb1). |
5. Network Configuration and Scanning
| Command | Purpose | Explanation |
|---|---|---|
ip a |
View IP Addresses | Displays address information for all network interfaces (modern replacement for ifconfig). |
ifconfig |
Network Config (Legacy) | Older command to display/configure network interfaces. |
iw dev |
Wireless Info | Shows detailed information about wireless devices. |
sudo iwconfig |
Wireless Config | Displays/sets basic wireless interface parameters. |
sudo ip link set wlan1 down |
Disable Interface | Brings down the specified wireless interface. |
sudo ip link set wlan1 name wlan1mon |
Rename Interface | Renames the wireless interface (useful for monitor mode setup). |
airmon-ng |
Monitor Mode | Puts a wireless card into monitor mode for security auditing. |
sudo arp-scan -l++ |
ARP Scan | Scans the local network segment using ARP packets to discover active hosts. |
ARP Scan Usage Example:
cd /tmp/
sudo arp-scan -l++
6. Wireless Adapter (Alfa/Realtek) Setup
This covers installing the rtl88xxau or rtl8812au driver, often needed for high-power Wi-Fi adapters.
Option 1: Apt Repository (DKMS)
sudo apt install realtek-rtl88xxau-dkms
Option 2: Compile from Source (for rtl8812au)
sudo apt install git dkms build-essential
git clone https://github.com/aircrack-ng/rtl8812au.git
cd rtl8812au
sudo make dkms_install
7. System Services and Control
| Command | Purpose | Explanation |
|---|---|---|
systemctl reboot -i |
Reboot System | Initiates a system reboot. |
sudo systemctl [command] [service] |
Manage Services | Standard format to control system services (e.g., start, stop, status, enable, disable). |
sudo systemctl disable hciuart.service |
Disable Bluetooth Console | Stops the service managing serial communications for the onboard Bluetooth chip (common on Raspberry Pi). |
sudo systemctl disable avahi-daemon.socket avahi-daemon.service |
Disable Avahi | Disables the Zeroconf/mDNS daemon used for local network discovery. |
8. Samba (Network File Sharing)
| Command | Purpose | Explanation |
|---|---|---|
sudo apt install -y usbmount |
Auto-Mount USB | Installs utility to automatically mount USB drives upon insertion. |
sudo apt install -y samba samba-common-bin |
Install Samba | Installs the core components for Windows/Linux file sharing. |
sudo tail -f /var/log/samba/log.smbd |
Monitor Samba Log | Displays the log file and follows it (-f) for real-time troubleshooting. |
9. Application Removal
| Command | Purpose | Explanation |
|---|---|---|
sudo apt remove -y triggerhappy dphys-swapfile plymouth |
Remove Apps | Uninstalls the specified packages. Often used to remove resource-intensive or unnecessary components: triggerhappy (hotkey daemon), dphys-swapfile (swap management), and plymouth (boot splash screen). |
10. System Stress and Temperature Monitoring
| Command | Purpose | Explanation |
|---|---|---|
sudo apt install stress-ng sysbench |
Install Stress Tools | Installs utilities to generate system load for testing stability. |
stress-ng --cpu 4 --timeout 300s |
CPU Stress Test | Puts a high load on 4 CPU cores for 300 seconds (5 minutes). |
watch -n 1 vcgencmd measure_temp |
Monitor Temperature | Runs the temperature command every 1 second (-n 1) to monitor heat output in real-time (Raspberry Pi). |
11. Fresh Install / Batch App Installation (One-Liner)
This script installs a comprehensive suite of development, network, and security tools.
sudo apt update && sudo apt upgrade -y && \
sudo apt install -y \
linux-cpupower screen tmux git git-lfs nano vim python3 python3-pip python3-venv \
python3-requests python3-yaml python3-tk python3-psutil \
wget curl jq unzip zip rsync tree expect build-essential pkg-config cmake \
dnsutils net-tools arp-scan iftop iotop lm-sensors sysstat smartmontools \
nmap mtr traceroute whois iperf3 tcpdump ncat netcat-traditional ethtool \
aircrack-ng reaver hashcat hydra netdiscover wifite screen tmux\
samba cifs-utils smbclient nfs-common sshfs rclone \
vnstat glances fail2ban logrotate \
ncdu htop btop lshw lsof parted \
psmisc moreutils figlet lolcat screenfetch \
avahi-daemon rsync
Alternative minimal install for screen/tmux:
sudo apt-get install screen tmux
Security and Ethical Considerations ⚠️
IMPORTANT: These tools are for authorized security testing only. Unauthorized access to networks is illegal. Always:
- Get written permission before testing
- Only test networks you own or have explicit authorization to test
- Follow responsible disclosure practices
- Comply with local laws and regulations
- Use for educational purposes in controlled environments
Legal Use Cases:
- Penetration testing with client authorization
- Security research in isolated lab environments
- Testing your own network security
- Educational purposes with proper supervision
- CTF (Capture The Flag) competitions
Last Updated: 2025-11-03