1. ls - List Directory Contents

The ls command lists the contents of a directory. It’s one of the most basic yet powerful commands.

Usage:

ls

Common Options:

• ls -l: Displays detailed information about files and directories.
• ls -a: Shows hidden files (files starting with a dot).
• ls -lh: Displays file sizes in human-readable format.

2. cd - Change Directory

Use the cd command to navigate through the file system on your server.

Usage:

cd /path/to/directory

• cd ..: Move up one level in the directory structure.
• cd ~: Go to the home directory.
• cd /: Go to the root directory.

3. top - Monitor System Processes

The top command provides a real-time view of system processes, CPU, and memory usage.

Usage:

top

Key Features:

• Monitor resource usage for each process.
• Kill unresponsive processes (press k and enter the process ID).
• Sort processes by CPU or memory usage (press M or P).

4. df - Disk Space Usage

The df command displays the available and used disk space for all mounted file systems.

Usage:

df -h

The -h flag shows the output in a human-readable format (GB, MB, etc.).

5. du - File and Directory Size

Use the du command to check the size of files and directories.

Usage:

du -sh /path/to/directory

• -s: Summarize the total size.
• -h: Display sizes in human-readable format.

6. grep - Search for Text in Files

The grep command allows you to search for specific text patterns within files.

Usage:

grep "search_term" filename

Example: Search for the word “error” in a log file:

grep "error" /var/log/syslog

7. chmod - Modify File Permissions

Use the chmod command to change file or directory permissions.

Usage:

chmod 644 filename

Common permission levels:

• 644: Read and write for the owner, read-only for everyone else.
• 755: Read, write, and execute for the owner; read and execute for others.

8. systemctl - Manage System Services

The systemctl command is essential for managing system services on systems running systemd.

Usage:

• systemctl status service-name: Check the status of a service.
• systemctl start service-name: Start a service.
• systemctl stop service-name: Stop a service.
• systemctl restart service-name: Restart a service.

9. tail - View End of a File

The tail command displays the last few lines of a file, which is useful for monitoring log files.

Usage:

tail -n 50 /var/log/syslog

Use tail -f to follow live updates in a file:

tail -f /var/log/syslog

10. reboot and shutdown - Restart or Power Off Server

Reboot or shut down your VPS server safely with these commands:

• sudo reboot: Reboots the server.
• sudo shutdown -h now: Powers off the server immediately.
• sudo shutdown -r now: Restarts the server.

Conclusion

Mastering these essential Linux commands is critical for managing and troubleshooting your VPS server efficiently. Whether you are monitoring processes, managing disk space, or restarting services, these commands will empower you to keep your server running smoothly and securely.