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Latchu@DevOps
Latchu@DevOps

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🚀 50 Real-Time Linux Commands for DevOps & System Admins

#aws #devops #linux #azure

If you're working with Linux in real-world environments—whether for DevOps, sysadmin, or cloud engineering—this guide provides 50 practical, scenario-based Linux command examples you’ll actually use on the job.

Each one includes a use case, command, and explanation. Bookmark this! 🔖

1. 🔥 Kill the Process Consuming the Most Memory

Scenario: Server lag due to memory-hungry process.

ps aux --sort=-%mem | head -n 5
kill -9 <PID>
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Explanation: Lists top memory users and kills the worst offender.

2. 🎧 Check Listening Ports and Services

Scenario: App fails to start—port in use.

ss -tuln
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3. 💽 Detect Excessive Disk Writers

Scenario: EBS filling up due to log/temp files.

sudo apt update && sudo apt install iotop -y
sudo iotop -o
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4. 🕒 Find Recently Modified Files (Last 2 Hours)

find /var/www -type f -mmin -120
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5. 🧑‍💻 List All Processes by a Specific User

ps -u username
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6. 👥 Create a Temporary User With Expiry

sudo useradd -e 2025-06-01 tempuser
sudo passwd tempuser
sudo chage -d 0 tempuser
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7. 🔎 Find the Process Listening on a Specific Port

sudo lsof -i :8080
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8. 🧠 Monitor Real-Time CPU Usage

top -o %CPU
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9. ⏰ List All Cron Jobs for a User

crontab -u ubuntu -l
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10. 📦 Backup Only .conf Files With Folder Structure

rsync -av --prune-empty-dirs \
  --include='*/' \
  --include='*.conf' \
  --include='**/*.conf' \
  --exclude='*' \
  /etc/nginx/ backup/nginx/
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11. 📋 Check Logs From Previous Boot

journalctl -b -1
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12. 📊 Check Uptime and Load Averages

uptime
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13. 🧟 Find Zombie Processes

ps aux | awk '$8=="Z" { print $0 }'
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14. 💾 Find Directories Using Most Disk Space

du -h --max-depth=1 / | sort -hr
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15. 🔍 Display Top 10 Largest Files in Directory Tree

find /var -type f -exec du -h {} + | sort -rh | head -n 10
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16. 📈 Check Inode Usage

df -i
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17. 📝 Monitor Real-Time Logs (systemd services)

journalctl -u nginx.service -f
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18. 🌲 Monitor Real-Time Process Tree

pstree -p
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19. 👀 Check Who Is Logged In

w
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20. 🗡 Kill All Processes Belonging to a User

pkill -u tempuser
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21. ❗ Watch Logs for "error" Messages in Real-Time

tail -f /var/log/syslog | grep -i --line-buffered "error"
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22. 🌐 Check DNS Resolution

dig api.example.com +short
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23. 📉 Limit Bandwidth While Using wget

wget --limit-rate=1m https://your-download-url
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24. ⏲ Reboot System in 60 Seconds With Warning

sudo shutdown -r +1 "Rebooting for maintenance. Save your work."
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25. 🧠 Watch Memory & CPU Usage of a Process

watch -n 2 "ps -p <PID> -o %cpu,%mem,cmd"
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26. ⌛ Schedule One-Time Task with at

echo "reboot" | at now + 15 minutes
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27. 🔗 Run Command Only if Previous One Succeeded

git pull && ./build.sh
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28. 🔁 Retry Until a Command Succeeds

until curl -s http://localhost:8080/health; do sleep 5; done
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29. 📦 Create Compressed Tarball

tar -czvf backup.tar.gz /path/to/folder
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30. 📂 Extract a Tar.gz Archive

tar -xzvf backup.tar.gz
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31. 💿 Show Disk Usage by Mounted Partition

df -h
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32. 💽 Show Mounted Disks and Filesystems

lsblk -f
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33. 🧮 Show Memory Usage Summary

free -h
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34. 📦 List All Installed Packages (Debian)

dpkg -l
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35. 🔄 Update and Upgrade All Packages

sudo apt update && sudo apt upgrade -y
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36. 📜 Check Last 100 Lines of Nginx Log

tail -n 100 /var/log/nginx/access.log
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37. 🔍 Recursively Search Files for Keyword

grep -r "TODO" .
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38. 🔐 Securely Copy File to Remote Server

scp file.txt user@host:/remote/path/
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39. 🚨 Find .log Files > 100MB

find /var/log -name "*.log" -size +100M
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40. 🌐 Show All Open Network Connections

netstat -tulnp
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41. 🔧 Manage Services with systemctl

sudo systemctl start nginx         # Start service  
sudo systemctl enable nginx        # Enable at boot  
sudo systemctl status nginx        # Check status
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42. 📡 Monitor Network Usage (iftop)

sudo apt install iftop -y
sudo iftop
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43. 🧪 Manage Environment Variables

printenv                # View env vars  
export MY_VAR=value     # Set temporarily
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44. 👤 User and File Ownership/Permissions

cut -d: -f1 /etc/passwd          # List users  
ls -l filename                   # Check file ownership  
sudo chown user:group file       # Change owner  
chmod +x script.sh               # Make script executable
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✅ Final Thoughts

These are not just commands—they’re real-world solutions to real-world problems. Whether you're troubleshooting a server spike, preparing a production deployment, or cleaning up a messy filesystem, this cheat sheet can save your day.

💬 Have a favorite Linux trick? Share it in the comments!

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