Essential Linux Commands for Cybersecurity

Introduction

• Focus on essential Linux commands for ethical hacking and cybersecurity
• Importance of mastering these basics before moving on to advanced tools (e.g., Metasploit, nmap)
• Use Terminal for navigating Linux filesystem

Navigating the Linux Filesystem

ls Command

• Basic listing of directory contents
• ls -l: Long listing format, shows more details (e.g., file permissions, owner, size)
• ls -a: Shows hidden files
• ls -t: Sorts by modification time
• ls -h: Human-readable file sizes
• Combine options: ls -lath

cd Command

• cd: Change directory
• cd -: Return to the previous directory
• cd ..: Move up one directory level
• cd ~: Go to the home directory
• Tab completion for directories

pwd Command

• pwd: Print working directory

Manipulating Files and Directories

touch Command

• touch filename: Create empty text files

mkdir Command

• mkdir directory_name: Create a new directory
• mkdir -p path/to/directory: Create nested directories
• mkdir -m 777 directory_name: Create a directory with specific permissions

cp Command

• cp source destination: Copy files
• cp -r source destination: Copy directories recursively

rm Command

• rm filename: Remove files
• rm -r directory: Remove directories recursively
• rm *pattern*: Remove files matching a pattern

mv Command

• mv source destination: Move or rename files

clear Command

• clear: Clear the terminal screen

File Viewing and Editing

cat Command

• cat filename: View file contents
• cat file1 file2 > newfile: Concatenate files
• cat file >> existingfile: Append to a file

tail Command

• tail filename: View the last 10 lines of a file
• tail -n N filename: View the last N lines
• tail -f filename: Continuously monitor a file

head Command

• head filename: View the first 10 lines of a file
• head -n N filename: View the first N lines

less and more Commands

• less filename: View file one page at a time, supports search
• more filename: Simpler than less, also views file one page at a time

Text Editors

• vi filename: Open file in vi editor (more complex, powerful)
• nano filename: Open file in nano editor (user-friendly)

Process Management

ps Command

• ps: Show processes for current user
• ps aux: Detailed process listing

top Command

• top: Real-time process monitoring
• top -u username: Show processes for a specific user
• top -p PID: Monitor a specific process

kill Command

• kill PID: Terminate a process
• kill -9 PID: Forcefully terminate a process

Job Control

• command &: Run command in background
• jobs: List background jobs
• fg: Bring background job to foreground

Networking

ifconfig Command (Deprecated)

• ifconfig: Show network interfaces

ip Command

• ip a: Show IP addresses
• ip route show: Show routing table
• ip addr add IP/Mask dev interface: Add an IP address

netstat and ss Commands

• netstat: Show network connections
• ss: Socket statistics, newer than netstat
• ss -t: Show TCP connections
• ss -u: Show UDP connections

SSH and SCP

• ssh user@host: Connect to a remote system
• scp source user@host:destination: Secure copy files between hosts

Checking System Info

uname Command

• uname -a: Show system information

df Command

• df: Show disk space usage
• df -h: Human-readable format

Finding Files

find Command

• find /path -name filename: Find files by name
• find /path -size +1M: Find files larger than 1MB
• find /path -mtime -30: Find files modified in the last 30 days

grep Command

• grep pattern file: Search for a pattern in a file
• grep pattern /path/*: Search for a pattern in multiple files*

Archiving and Compression

tar Command

• tar czf archive.tar.gz files: Create a compressed archive
• tar xzf archive.tar.gz: Extract a compressed archive
• tar rf archive.tar file: Add files to an archive

gzip Command

• gzip file: Compress a file
• gunzip file.gz: Decompress a file
• gzip -l file.gz: List contents of a gzip file

User Management

Adding and Deleting Users

• useradd username: Add a new user
• userdel username: Delete a user
• useradd -m username: Add a user with a home directory
• useradd -G group username: Add a user to a specific group

Adding and Deleting Groups

• groupadd groupname: Add a new group
• groupdel groupname: Delete a group

Conclusion

• Mastering these basic Linux commands is essential for anyone in cybersecurity
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