Stage 5: Practice Legend

Enable learners to apply all scenario‑based troubleshooting skills in a capstone challenge. Build confidence in diagnosing, solving, and explaining complex Linux problems under interview conditions.

Hackbook Overview

• Capstone Focus: Combine permissions, services, networking, configs, and disk usage into one scenario.
• Systematic Approach: Symptoms → Logs → Configs → Permissions → Networking → Disk.
• Interview Angle: Employers want to see clear, structured problem‑solving and communication.
• Best Practice: Document steps, explain reasoning, and propose sustainable fixes.

Hands‑On Practice

• Simulate a web server outage: misconfigure Nginx, block port 80, and fix both issues.
• Create a disk full scenario: fill /var/log with dummy files, then clean and implement log rotation.
• Break SSH access: misconfigure /etc/ssh/sshd_config, troubleshoot, and restore secure login.
• Combine permissions + group issues: restrict a shared directory, then resolve access for multiple users.

Interview Question Bank

Conceptual

• Q1. Why is a structured troubleshooting approach important?
  A1. It ensures problems are solved efficiently, avoids guesswork, and builds confidence in interviews.
• Q2. What makes scenario‑based questions different from simple command questions?
  A2. They test holistic problem‑solving across multiple subsystems, not just isolated commands.

Practical

• Q3. A web server is running but inaccessible externally. How do you solve it?
  A3. Check service status (systemctl status nginx), verify firewall rules (firewall-cmd --list-all), and confirm port 80/443 is open.
• Q4. Disk usage reaches 100% and services crash. What’s your process?
  A4. Run df -h to confirm, clean logs/temp files, implement logrotate, and restart services.
• Q5. SSH login fails after config changes. How do you troubleshoot?
  A5. Test syntax (sshd -t), check /etc/ssh/sshd_config, and review logs in /var/log/auth.log.

Scenario‑Based

• Q6. A user cannot access a shared directory despite correct group membership. What’s your solution?
  A6. Check directory permissions (ls -ld), confirm group membership (groups user), and adjust with chmod g+rwx.
• Q7. A service fails after every reboot. How do you design a fix?
  A7. Enable the service (systemctl enable <service>), verify dependencies, and test across reboots.
• Q8. A web app fails due to both config and firewall issues. How do you explain your solution?
  A8. Fix config syntax (nginx -t), reload service, adjust firewall rules, and document changes for sustainability.

Behavioral Based

• Q9. Tell me about a time you solved a complex Linux scenario end‑to‑end.
  A9. Example: “I restored a production service by fixing Nginx config, reopening firewall ports, and adjusting permissions — then documented the solution for the team.”

Cheatsheet (Quick Notes)

• Troubleshooting Steps: Symptoms → Logs → Configs → Permissions → Networking → Disk.
• Web Servers: systemctl status, nginx -t, firewall rules.
• Disk Issues: df -h, du -sh, logrotate.
• SSH Issues: /etc/ssh/sshd_config, /var/log/auth.log.
• Permissions: chmod, chown, groups.