Essential Linux Commands for Cyber Security

Introduction

• Presenter: Neilson Networking
• Topic: Essential Linux commands and their special flags
• Target Audience: Beginners in ethical hacking and cybersecurity
• Advanced Topics: Metasploit, Nmap, Hydra (covered in other videos)

Navigating the Linux File System

• Methods: GUI vs. Terminal
  • GUI: File Explorer, Nautilus
  • Terminal (preferred method)

Commands

1. ls (List Directory Contents)
   • ls: Basic listing
   • ls -l: Long listing
     • Details Provided: Links, permissions, owner, group, size, modification date
   • ls -a: Show hidden files
   • ls -t: Sort by modification time
   • ls -h: Human-readable sizes
   • Combining Flags: ls -lath
2. cd (Change Directory)
   • cd [directory]: Navigate to a directory
   • cd -: Return to the previous directory
   • cd ..: Go up one level
   • cd ~: Go to home directory
   • Tab Completion: Use Tab key to auto-complete paths
3. pwd (Print Working Directory)
   • pwd: Shows the current directory
4. clear
   • clear: Clears the terminal screen

Manipulating Files and Directories

1. touch (Create Empty Files)
   • touch [filename]: Create an empty file
2. mkdir (Make Directory)
   • mkdir [directory_name]: Create a single directory
   • mkdir -p [directory_tree]: Create nested directories
   • mkdir -m 777 [directory_name]: Create directory with specific permissions
3. cp (Copy Files and Directories)
   • cp [source] [destination]: Copy files
   • cp -r [directory] [destination]: Copy directories recursively
4. rm (Remove Files and Directories)
   • rm [filename]: Remove a file
   • rm -r [directory]: Remove a directory recursively
   • rm [pattern*]: Remove files with a specific pattern
5. mv (Move/Rename Files and Directories)
   • mv [source] [destination]: Move or rename files/directories

Viewing Disk Usage

1. du (Disk Usage)
   • du: Shows disk usage of directories
   • du -h: Human-readable format
   • du -s: Summary of usage

File Permissions and Ownership

1. chmod (Change Mode/Permissions)
   • chmod [u|g|o]+/-[r|w|x] [file]: Modify permissions
   • chmod 777 [file]: Numeric method for setting permissions
2. chown (Change Ownership)
   • chown [user]:[group] [file]: Change file owner and group

Viewing and Combining File Contents

1. cat (Concatenate and Display Files)
   • cat [file]: Display file contents
   • cat [file1] [file2] > [newfile]: Combine files
   • echo [text] > [file]: Write text to a file
2. tail (Display End of File)
   • tail [file]: Display last 10 lines
   • tail -n [number] [file]: Display last n lines
   • tail -f [file]: Follow file changes
3. head (Display Start of File)
   • head [file]: Display first 10 lines
   • head -n [number] [file]: Display first n lines
4. less & more (Page Through Files)
   • less [file]: View file one page at a time
   • more [file]: Similar to less, but less feature-rich

Text Editors

1. vi/vim
   • vi [file]: Open file in vi editor
   • Edit Mode: i (Insert)
   • Command Mode: : (colon), followed by commands like w (write), q (quit)
2. nano
   • nano [file]: Open file in nano editor
   • User-Friendly: Easier for beginners

Process Management

1. ps (Process Status)
   • ps: Shows processes for current user
   • ps aux: Detailed process listing
2. top (Real-Time Process Overview)
   • top: Real-time process monitoring
   • top -u [username]: Filter by user
3. kill (Terminate Process)
   • kill [PID]: Terminate process by PID
   • kill -9 [PID]: Forcefully terminate process
4. jobs (Background Jobs)
   • jobs: List background jobs
   • bg: Resume a job in background
   • fg: Bring job to foreground

Networking Commands

1. ifconfig (Network Interface Configuration)
   • ifconfig: Deprecated but shows network configuration
2. ip (Newer Network Configuration Tool)
   • ip addr: Show IP addresses
   • ip route: Show routing table
   • ip addr add [IP] dev [interface]: Add IP address to interface
3. netstat (Network Statistics)
   • netstat -l: Show listening ports
4. ss (Socket Statistics)
   • ss -t: Show TCP sockets
   • ss -u: Show UDP sockets
   • ss -p: Show processes using sockets
5. ssh (Secure Shell)
   • ssh [user]@[host]: Connect to remote machine
6. scp (Secure Copy)
   • scp [local_file] [user]@[host]:[remote_file]: Copy file to remote machine
7. rsync (Remote Sync)
   • rsync [options] [source] [destination]: Sync files and directories

System Information

1. uname (System Information)
   • uname -a: Detailed system information
2. df (Disk Free)
   • df -h: Shows disk space usage in human-readable format

Searching Files

1. find (Search for Files)
   • find [path] -name [pattern]: 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
2. grep (Search Within Files)
   • grep [pattern] [file]: Search for pattern in file
   • grep -r [pattern] [directory]: Recursively search in directory

Archiving and Compressing Files

1. tar (Tape Archive)
   • tar czf [archive.tar.gz] [files]: Create compressed archive
   • tar xzf [archive.tar.gz]: Extract compressed archive
2. gzip (Compress Files)
   • gzip [file]: Compress file
   • gunzip [file.gz]: Decompress file

User Management

1. useradd (Add User)
   • useradd [username]: Add new user
   • useradd -m [username]: Add user with home directory
   • useradd -g [group] [username]: Add user to specific group
   • useradd -e [date] [username]: Add user with expiration date
2. userdel (Delete User)
   • userdel [username]: Delete user
   • userdel -r [username]: Delete user and home directory
3. groupadd (Add Group)
   • groupadd [groupname]: Add new group
4. groupdel (Delete Group)
   • groupdel [groupname]: Delete group

Conclusion

• Goal: Provide essential Linux commands necessary for cybersecurity beginners
• Further Learning: Advanced tools and commands like Metasploit, Nmap, Hydra in other videos
• Call to Action: Like, subscribe, and stay tuned for more content