Essential Linux Commands & System Administration Toolkit

File Operations

• ls — List files and directories (-a for hidden, -l for detailed)
• cd [directory] — Change directory
• mkdir [directory] — Create directory
• cp [source] [destination] — Copy files/directories (-r for recursive)
• mv [source] [destination] — Move or rename files/directories
• rm [file] — Remove files (-r for recursive)
• chmod [permissions] [file] — Change file permissions
• chown [user]:[group] [file] — Change file ownership

System Monitoring

• top / htop — Monitor system processes
• ps — List running processes
• df -h — Display disk space usage
• free -m — Show memory usage

Networking Commands

• ifconfig / ip a — Display network interfaces
• ping [host] — Test network connectivity
• netstat -tuln — List network connections
• nmap [IP] — Scan networks and ports

Package Management

• Debian-based: apt-get, apt
• Red Hat-based: yum, dnf
• Arch Linux: pacman
• SUSE Linux: zypper
• General: snap, flatpak

User Management

• useradd [user] — Add a new user
• usermod [user] — Modify user account
• passwd [user] — Change user password
• su [user] — Switch user
• sudo [command] — Execute command as superuser

Nano Editor Commands

• Ctrl + O — Save file
• Ctrl + X — Exit Nano
• Ctrl + W — Search within the file
• Ctrl + K — Cut line
• Ctrl + U — Paste line
• Ctrl + G — Display help

Vim Editor Commands

• Modes: i (Insert), Esc (Command)
• Saving & Quitting: :w (Save), :q (Quit), :wq (Save & Quit), :q! (Quit without saving)

Vim Navigation

• h j k l — Move cursor
• /pattern — Search for a pattern
• :set nu — Show line numbers

Shell Scripting: Variables

• var_name="value" — Assign a value to a variable

Shell Scripting: Loops

• for i in {1..5}; do echo $i; done — Loop from 1 to 5
• while [ condition ]; do echo "looping"; done — Execute a while loop
• for file in *.txt; do echo $file; done — Loop through .txt files

Shell Scripting: Conditionals

• if [ condition ]; then echo "True"; elif [ condition ]; then echo "Else if"; else echo "False"; fi — If-elif-else statement
• if [[ $var -eq 10 ]]; then echo "Equal to 10"; fi — Conditional check for equality

Wireless Network Commands

• iwconfig — Display wireless configuration
• airmon-ng — Enable monitor mode for Wi-Fi adapter

Port Scanning Tools

• nmap -sS -A — Perform SYN scan with OS detection

Packet Capture

• tcpdump — Capture network traffic

Basic SSH Commands

• ssh user@host — Connect to a remote host
• scp source user@host:destination — Securely copy files to/from a remote host

SSH Key Management

• ssh-keygen — Generate SSH keys
• ssh-copy-id user@host — Copy public key to a remote host

Git Basic Commands

• git init — Initialize a new Git repository
• git clone URL — Clone a repository from a URL
• git add [file] — Stage changes for commit
• git commit -m "message" — Commit staged changes with a message
• git push / git pull — Push/pull changes to/from a remote repository

Git Branching

• git branch — List all branches
• git checkout branch_name — Switch to a different branch
• git merge branch_name — Merge a branch into the current branch

Important Configuration Files

• /etc/hosts — Static hostname-IP mapping
• /etc/fstab — Disk and partition mount settings
• /etc/network/interfaces — Network configuration (Debian-based systems)
• ~/.bashrc, ~/.zshrc — User-specific shell startup scripts
• /etc/systemd/system/ — Systemd service unit files

System Log Files

• /var/log/syslog — General system log
• /var/log/auth.log — Authentication log

Nmap Scan Options

• -sS — TCP SYN scan
• -A — Enable OS detection and version detection
• -Pn — Disable ping before scanning

Wireshark Display Filters

• ip.addr == 192.168.1.1 — Filter by IP address
• tcp.port == 80 — Filter by TCP port

Wireless Attack Tools: Scanning

• scan — Scan for all access points
• scan -ch 6 — Scan on a specific channel
• scan stations -ch 6 — Scan connected devices (stations)

Wireless Attack Tools: Selecting Targets

• select ap 0 — Select an Access Point by ID
• select station 2 — Select a station by ID
• show selected aps / show selected stations — Show currently selected APs/Stations

Wireless Attack Tools: Attack Commands

• attack deauth -ap 0 -st 2 — Perform a deauthentication attack on a specific station
• attack beacon -b — Initiate a beacon flood attack
• attack probe -ap 0 — Launch a probe flood attack
• enable random 5 — Enable random SSID attack (5-second interval)
• stop attack — Stop all active attacks

Wireless Attack Tools: Utility Commands

• clear — Clear the console
• sysinfo — Display system information
• reboot — Reboot the device
• format — Format the SPIFFS filesystem

Regular Expressions (Regex) Commands

• grep "pattern" file.txt — Search for a pattern within a file
• sed 's/old/new/g' file.txt — Replace text using sed

Docker Commands

• docker run image — Run a Docker container from an image
• docker ps — List running Docker containers
• docker stop container_id — Stop a running Docker container