Add User: sudo adduser [username]

Delete User: sudo deluser [username]

Change Password: passwd [username]

Add to Group: sudo usermod -aG [groupname] [username]

Switch User: su - [username]

Run as Root: sudo [command]

Search for Text: grep "pattern" [file], grep -r "pattern" [directory] (recursive)
Find Files: find [path] -name "pattern" (e.g., find . -name "*.log")
Edit File (Nano): nano [file_name]
Edit File (Vim/Vi): vi [file_name] (i for insert, Esc then :wq for save/exit, :q! for exit without save)
Sort Lines: sort [file]
Unique Lines: uniq [file]
Count Lines/Words/Chars: wc [file]
Stream Editor: sed 's/old/new/g' [file] (substitute all 'old' with 'new')
Column Extractor: awk '{print $1}' [file] (print first column)

Redirection:
- > (redirect stdout to file, overwrite)
- >> (redirect stdout to file, append)
- 2> (redirect stderr to file)
- &> (redirect stdout & stderr to file)
Piping: command1 | command2 (output of command1 becomes input of command2)
Command Chaining:
- cmd1; cmd2 (run cmd1 then cmd2)
- cmd1 && cmd2 (run cmd2 only if cmd1 succeeds)
- cmd1 || cmd2 (run cmd2 only if cmd1 fails)
Aliases: alias ll='ls -alF' (temporary), add to ~/.bashrc for permanent
Environment Variables: export VAR="value", echo $VAR
Scheduled Tasks (Cron): crontab -e (edit user's crontab)
- Syntax: * * * * * command (minute, hour, day of month, month, day of week)
SSH: ssh [user]@[host] (secure shell)
SCP: scp [source] [destination] (secure copy, e.g., scp file.txt user@remote:/path/)

History Search: Ctrl+R then type to search command history
Command Line Editing:
- Ctrl+A: Go to beginning of line
- Ctrl+E: Go to end of line
- Ctrl+K: Delete from cursor to end of line
- Ctrl+U: Delete from cursor to beginning of line
- Alt+F: Move forward one word
- Alt+B: Move backward one word
Shell Scripting Basics:
- Shebang: #!/bin/