Linux for DevOps

How Much Prep and Practice Is Enough to Get You Ready for Interviews?

Author

Vishakha Sadhwani
August 18, 2025

Hi Inner Circle,

Everyone keeps saying, “Learn Linux for DevOps” — but what does that actually mean?

The truth is, Linux isn’t just a topic to check off your list.

It’s the foundation of almost everything you do as a DevOps engineer — from running containers to provisioning infrastructure to debugging failures in production.

In this edition, I’ll walk you through:

  • Why Linux matters in DevOps workflows

  • Where it shows up in your day-to-day work

  • Real interview-style questions and scenarios

  • Getting Started: Projects and Resources

  • Also Linux command cheatsheet for reference

Let’s get into it.

Why Linux Skills Are Critical in DevOps

Whether you’re:

  • Deploying a Kubernetes cluster

  • Automating cloud infrastructure with Terraform or Pulumi

  • Troubleshooting a failed build pipeline

There’s a high chance you’re doing it on a Linux system — with a terminal open.

Linux powers the execution layer behind containers, cloud servers, CI/CD runners, monitoring agents, and more. So when interviews test Linux, they’re not testing if you know every flag of a command — they’re evaluating if you can debug real-world problems confidently and efficiently.

Linux for DevOps — Real-World Scenarios and How to Approach Them

1. A deployment failed and your app isn’t coming back up. How do you troubleshoot it on a Linux server?

What they’re evaluating: Your process for debugging services, logs, and file systems.

Sample approach:

  • SSH into the instance

  • Check service status:
    systemctl status <service>

  • View recent logs:
    journalctl -xe

  • Inspect running processes:
    ps aux | grep <app>

  • Check disk usage:
    df -h

  • Validate file permissions:
    ls -lah <config-path>

    (to ensure the service isn’t failing due to access issues, check file permissions and ownership - misconfigured chmod or missing execute rights often break deployments silently)

2. You’re asked to find and kill all processes using more than 80% CPU.

What they’re evaluating: Your ability to monitor and manage resources efficiently.

Sample approach:

  • Use top to confirm visually

  • Automate with: 

    ps aux | awk '$3 > 80 {print $2}' | xargs kill -9

    • $3 = CPU usage

    • awk filters processes using >80% CPU

    • xargs kill -9 force-kills them

  • Validate CPU drop using uptime or top

3. Logs aren’t rotating and disk is filling up. What do you check?

What they’re evaluating: Knowledge of logging systems and disk inspection.

Sample approach:

  • Check disk usage:
    df -h

  • List log files by size:
    ls -lhS /var/log

  • Simulate logrotate:
    logrotate -d /etc/logrotate.conf

  • Check cron job execution:
    crontab -l
    grep CRON /var/log/syslog

4. You need to regularly fetch the last 100 lines of a 2GB log file.

What they’re evaluating:
Your ability to work with large log files efficiently and automate simple data extraction.

Sample approach:

Step 1: Use tail for fast access

tail -n 100 /path/to/large.log

  • tail: Outputs the end of a file.

  • -n 100: Prints the last 100 lines only (avoiding memory-heavy operations like opening the whole file in an editor).

  • Efficient because it reads from the end — ideal for logs that grow over time.

Step 2: Automate with a script

#!/bin/bash
tail -n 100 /path/to/large.log >> /var/log/summary.log
#Schedule using cron
#Edit the crontab:
crontab -e
#and add this line:
*/30 * * * * /path/to/script.sh

Cron breakdown:

  • */30: Every 30 minutes

  • *: (Every hour) *: (Every day of the month) *: (Every month) *: (Every day of the week)

This means: run the script every 30 minutes — like at 00:00, 00:30, 01:00, 01:30, and so on.

5. You want to monitor CPU, memory, and disk usage every 30 minutes.

What they’re evaluating:
Your ability to write lightweight monitoring scripts and log system health data over time.

Sample Approach:

Step 1: Write the script

#!/bin/bash
echo "=== $(date) ===" >> /var/log/resource.log

# Top 5 lines from top command (includes load averages, tasks, CPU usage)
top -b -n1 | head -5 >> /var/log/resource.log

# Disk usage
df -h >> /var/log/resource.log

# Memory usage
free -m >> /var/log/resource.log

# cron job
#and add this line:
*/30 * * * * /var/log/resource.log

Over time, this log helps identify usage patterns or investigate system slowdowns — and it’s a great talking point in interviews for showing initiative and scripting capability.

These are just a few scenario-based questions and sample answers.

Remember — there’s no single right or wrong answer, it’s the approach that truly matters.

Practice with Intention

Instead of memorizing commands, ask yourself:

  • When would I use this in my workflow?

  • What type of failure would this solve?

  • Could I explain this to someone else (or in an interview)?

Getting Started: Projects and Resources

Spin up a Linux VM (or use free credits):

Follow structured tutorials:

Document your journey on GitHub:

Use folders per topic, commit your scripts and notes, and write README files with explanations. Sharing your work boosts retention and visibility.

Top GitHub Repos to Learn Linux

Final Thoughts

Linux isn’t just one of many tools — it’s the environment where nearly everything runs.

If you want to build real DevOps confidence:

  • Focus on real scenarios, not rote commands

  • Practice by writing and tweaking scripts

  • Build your mental model of the Linux environment

See you Thursday — we’ll break down how Git actually works under the hood and how to debug it when your pipelines go wrong.

— Vishakha

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