10 essential linux commands for aspiring sysadmins

essential linux commands aspiring sysadmins
April 11, 2025
4 min read
By Cojocaru David & ChatGPT

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10 Essential Linux Commands Every Aspiring SysAdmin Should Master

Mastering Linux commands is non-negotiable for aspiring system administrators. Whether you’re troubleshooting servers, managing files, or automating tasks, these 10 essential Linux commands will give you the foundational skills to work efficiently. Below, we break down each command with practical examples and key options to help you gain confidence in the terminal.

1. ls – List Directory Contents

The ls command displays files and directories, giving you a quick snapshot of your current location.

Key Options:

  • ls -l: Detailed view (permissions, owner, size, modification date).
  • ls -a: Shows hidden files (starting with .).
  • ls -h: Human-readable file sizes (KB, MB, GB).
  • ls -t: Sorts by modification time (newest first).

Example:

ls -lath

Combines multiple flags for a comprehensive directory overview.

2. cd – Change Directory

Navigate the filesystem effortlessly with cd.

Common Uses:

  • cd /path/to/dir: Move to an absolute path.
  • cd ..: Go up one directory.
  • cd ~: Return to your home directory.
  • cd -: Switch back to the previous directory.

Example:

cd /var/log

Jumps to the system logs directory.

3. grep – Search Text Patterns

Find specific text in files quickly with grep.

Useful Flags:

  • grep -i: Case-insensitive search.
  • grep -r: Recursive search (includes subdirectories).
  • grep -v: Exclude matching lines.
  • grep -n: Show line numbers.

Example:

grep -i "error" /var/log/syslog

Searches for “error” in system logs, ignoring case.

4. chmod – Change File Permissions

Control file access with chmod for better security.

Permission Basics:

  • chmod 755 file: Owner gets rwx, group/others get rx.
  • chmod +x script.sh: Makes a script executable.
  • chmod u=rwx,g=rx,o=r file: Symbolic permission assignment.

Example:

chmod 644 config.conf

Sets read/write for owner, read-only for others.

5. sudo – Execute Commands as Superuser

Run administrative tasks safely with sudo.

Best Practices:

  • Limit sudo usage to reduce risks.
  • sudo -u user command: Run as a specific user.

Example:

sudo apt update

Updates package lists (requires root).

6. df – Check Disk Space Usage

Monitor storage with df.

Helpful Options:

  • df -h: Human-readable sizes.
  • df -T: Shows filesystem types.

Example:

df -hT

Displays disk usage and filesystem types.

7. top – Monitor System Processes

Get real-time system performance insights.

Key Features:

  • Press P to sort by CPU usage.
  • Press M to sort by memory usage.
  • Press 1 to view per-core stats.

Example:

top

Launches the interactive process viewer.

8. tar – Archive Files

Bundle and compress files efficiently.

Common Commands:

  • tar -czvf backup.tar.gz /home/user: Creates a compressed archive.
  • tar -xvzf backup.tar.gz: Extracts a gzipped archive.

Example:

tar -czvf logs.tar.gz /var/log

Compresses log files into a single archive.

9. ssh – Secure Remote Access

Connect to remote servers securely.

Basic Usage:

  • ssh user@hostname: Standard remote login.
  • ssh -p port user@host: Custom port connection.

Example:

ssh admin@192.168.1.100

Logs into a server as admin.

10. systemctl – Manage System Services

Control background services with systemctl.

Essential Commands:

  • systemctl start nginx: Starts the Nginx service.
  • systemctl status nginx: Checks service status.
  • systemctl enable nginx: Auto-starts on boot.

Example:

systemctl restart nginx

Restarts the Nginx web server.

“The Linux philosophy is ‘Do one thing and do it well.’” — Linus Torvalds

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