15 Must-Know Linux Commands for Junior Systems Engineers

1. Why the CLI Is Your Best Friend

• Speed and Efficiency: Command chaining, piping, and direct text input make the CLI faster than GUIs.
• Precision and Flexibility: Tools like grep, awk, and sed allow for fine-tuned text processing.
• Remote Configuration: CLI tools are ideal for managing remote servers via SSH.
• Scripting and Automation: Bash scripts and cron jobs automate repetitive tasks.

Learn more about the benefits of the CLI in this
in-depth article on Linux command line usage.

2. Navigating the Linux File System

• ls – Lists directory contents. Example: ls -l for detailed information.
• cd – Changes directory. Example: cd /var/log to navigate into the log folder.
• pwd – Prints the current working directory. Example: pwd.

For further reading, check out the
Linux Command Library.

3. File and Directory Management Essentials

• cp – Copies files or directories. Use cp -R for the recursive copy.
• mv – Moves or renames files. Example: mv old.txt new.txt.
• rm – Removes files or directories. Always use with caution (e.g., rm -ri for interactive deletion).
• mkdir – Creates directories. Example: mkdir my_folder.
• rmdir – Removes empty directories.

See this handy Hostinger Linux Commands Cheat Sheet for more details.

4. Working with File Permissions

• chmod – Changes file permissions. Example: chmod 755 script.sh.
• chown – Changes file ownership. Example: chown user:group file.txt.
• chgrp – Changes file group ownership.

For a deeper dive into permissions, read the
GNU Core Utilities documentation on chmod.

5. System Monitoring and Performance Tools

• top and htop – Monitor processes and resource usage in real-time.
• free – Displays memory usage. Example: free -h.
• df – Reports disk space usage. Example: df -h.
• du – Summarizes directory disk usage. Example: du -sh /path.

Check out this article on
system monitoring commands for more insights.

6. Managing Processes and Services

• ps – Displays information about running processes. Example: ps aux.
• kill – Terminates a process by its PID. Example: kill 12345.
• systemctl – Manages services on systemd systems. Example: systemctl restart nginx.
• service – Legacy command to manage services on SysV systems.

For more on process management, see the Red Hat blog on essential Linux commands.

7. Networking Commands for Junior Engineers

• ifconfig / ip address – Displays and configures network interfaces.
• ping – Tests connectivity. Example: ping -c 5 google.com.
• netstat / ss – Lists active network connections.
• traceroute – Traces the network path to a destination.
• nslookup / dig – Queries DNS information.

Learn more about networking commands on the
Linux man pages online.

8. Disk and Storage Management

• fdisk – Views and modifies disk partitions. Example: fdisk -l.
• lsblk – Lists block devices and their mount points.
• mount and umount – Mounts and unmounts file systems.
• blkid – Displays device UUIDs and labels.

For more details on disk management, visit the
DigitalOcean disk management tutorial.

9. Log Files and Troubleshooting

• tail – Shows the end of files. Example: tail -f /var/log/syslog for live updates.
• grep – Searches text for patterns. Example: grep "error" /var/log/syslog.
• journalctl – Views logs on systemd systems. Example: journalctl -u nginx.service.

More tips on troubleshooting logs can be found at
Linux Journal’s guide to journalctl.

10. Package Management

• Debian/Ubuntu: Use apt:
  • apt update – Update package lists
  • apt upgrade – Upgrade packages
  • apt install package_name – Install a package
• Red Hat/CentOS/Fedora: Use yum or dnf.
• Other tools include dpkg, rpm, and snap.

For a complete guide, check out the
DigitalOcean package management tutorial.

11. Archiving and Compression Commands

• tar – Archives and extracts files. Examples:
  • Create: tar -czvf archive.tar.gz /path/to/files
  • Extract: tar -xzvf archive.tar.gz
• gzip / gunzip – Compresses and decompresses files.
• zip / unzip – Creates and extracts ZIP archives.

Learn more about archiving with
the GNU tar manual.

12. Remote Server Management

• ssh – Securely connects to remote servers. Example: ssh user@remote_server.
• scp – Securely copies files between systems.
• rsync – Synchronizes files/directories efficiently. Example: rsync -avz /local/dir user@remote:/remote/dir.

For more on remote access, see the
DigitalOcean SSH tutorial.

13. Automation and Scripting Basics

• cron – Schedules recurring tasks. Edit your crontab with crontab -e.
• at – Schedules one-time tasks. Example: echo "reboot" | at 03:00.
• bash scripting – Write scripts to automate tasks. See the example below:

  #!/bin/bash
  # Backup Script Example
  SOURCE="/var/www/html"
  DEST="/backup/html-$(date +%F)"
  mkdir -p "$DEST"
  rsync -av --delete "$SOURCE" "$DEST"
  echo "Backup completed on $(date)" >> /var/log/backup.log
  

For more scripting tutorials, visit the LinuxCommand.org website.

14. Security Basics

• sudo – Executes commands with elevated privileges. Example: sudo apt update.
• passwd – Changes user passwords.
• ufw – Simple firewall management on Ubuntu. Example: sudo ufw allow 80.
• iptables – Advanced firewall configuration. Example: sudo iptables -A INPUT -p tcp --dport 22 -j ACCEPT.

Enhance your security knowledge by reading the Cyberciti.biz guide on Linux security.

15. Useful Shortcuts and Miscellaneous Commands

• history – Shows your command history. Example: history or repeat a command with !45.
• alias – Creates custom shortcuts. Example: alias ll="ls -alF".
• man – Displays the manual for commands. Example: man ls.
• clear – Clears the terminal screen.
• exit – Ends the terminal session.

For more productivity tips, check out this LifeWire article on Linux shortcuts.

Conclusion

Mastering these 15 essential Linux commands is a vital step in your journey as a systems engineer or administrator. By regularly practicing commands—from navigating directories with cd and ls to manage services with systemctl and configuring network settings—you unlock greater control, efficiency, and flexibility in managing your systems.

Recap:

• Navigation: ls, cd, pwd
• File Management: cp, mv, rm, mkdir
• Permissions: chmod, chown, chgrp
• Monitoring: top, free, df, du
• Process Management: ps, kill, systemctl
• Networking: ifconfig/ip, ping, traceroute
• Disk Management: fdisk, lsblk, mount
• Logs: tail, grep, journalctl
• Package Management: apt, yum, etc.
• Archiving: tar, gzip, zip
• Remote Management: ssh, scp, rsync
• Automation: cron, at, scripting
• Security: sudo, passwd, ufw, iptables
• Shortcuts: history, alias, man

Practice these commands daily, build your cheat sheet of aliases, and start automating routine tasks with simple bash scripts. Explore additional resources and join online communities such as the r/linux subreddit to further enhance your skills.

Happy command-line hacking!