Useful Linux Commands Reference

Table of Contents

1. Basic Commands
2. File Management
3. Process Management
4. Network
5. System Management
6. User Management
7. Advanced Commands
8. Tip
9. Useful Links

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1. Basic Commands

These commands allow navigation and interaction with the system:

• ls : Lists files and folders in the current directory.
  • Usage: ls -l displays files with details.
• cd : Changes the current directory.
  • Usage: cd /home/user to navigate to /home/user.
  • Go back to the parent directory: cd .. navigates to the parent directory.
• pwd : Displays the path of the current directory.
• clear : Clears the terminal screen.
• exit : Closes the terminal or current session.

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2. File Management

These commands help manage files and directories:

• cp : Copies files or folders.
  • Example: cp file.txt /destination copies file.txt.
• mv : Moves or renames files.
  • Example: mv file.txt /destination moves file.txt.
• rm : Deletes files or folders.
  • Example: rm file.txt deletes file.txt.
  • Delete a folder: rm -r folder.
• mkdir : Creates a new folder.
  • Example: mkdir new_folder.
• rmdir : Deletes an empty folder.
  • Example: rmdir empty_folder.

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3. Process Management

These commands allow monitoring and controlling system processes:

• ps : Lists running processes.
  • Example: ps aux displays all active processes.
• top : Displays real-time processes.
• kill : Terminates a process.
  • Example: kill -9 PID forcefully stops the process with the specified PID.
• htop : Interactive alternative to top.

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4. Network

These commands help manage network connections:

• ping : Tests network connectivity to an address.
  • Example: ping google.com.
• ifconfig (or ip a) : Displays network information.
• netstat : Shows active network connections.
• traceroute : Traces the path to a network destination.
  • Example: traceroute google.com.

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5. System Management

These commands provide system information and control:

• uname -a : Displays information about the system.
• df -h : Shows used and available disk space.
• free -h : Displays memory usage.
• uptime : Shows how long the system has been running.
• reboot : Restarts the system.
• shutdown : Shuts down the system.
  • Example: shutdown -h now shuts down immediately.

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6. User Management

These commands allow managing system users:

• whoami : Displays the current user's name.
• adduser : Adds a new user.
• passwd : Changes the user's password.
• who : Shows logged-in users.

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7. Advanced Commands

These commands are useful for specific tasks:

• sudo : Runs a command as the administrator.
• chmod : Changes file permissions.
  • Example: chmod 755 file.txt.
• chown : Changes file ownership.
  • Example: chown user:user file.txt.
• tar : Compresses or decompresses files.
  • Example: tar -czvf archive.tar.gz folder.

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Tip

You can combine commands with redirections:

• command > file.txt : Saves the output to a file.
  • Example: ls > file_list.txt.
• command >> file.txt : Appends the output to an existing file.

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Useful Links

• Official Linux Documentation
• GNU Linux Commands