Interview Questions

By Ravindra Bagale Last updated: 25 September 2026

Q1. How do you find the top 10 IP addresses in an Nginx access log?: awk '{print $1}' access.log | sort | uniq -c | sort -rn | head
Q2. What is the difference between > and >>? What does 2>&1 do?: > overwrites a file, >> appends. 2>&1 redirects standard error to wherever standard output is going.
Q3. How do you check which ports a Linux server is listening on?: sudo ss -tlnp (or the older netstat -tlnp).
Q4. What is the difference between service <name> restart and service <name> reload?: restart stops and starts the service (brief downtime). reload asks the service to re-read its configuration without dropping existing connections (if supported).
Q5. What is the difference between service and systemctl?: systemctl is the native systemd tool. service is an older wrapper that, on systemd systems, forwards start/stop/restart/reload/status to systemctl. Enabling at boot (systemctl enable) and daemon-reload require systemctl.
Q6. Explain the five fields of a cron expression.: Minute, hour, day of month, month, day of week — e.g. 30 2 * * 1 runs at 02:30 every Monday.
Q7. How do you see the logs of a systemd service?: journalctl -u <service>; add -f to follow live, -n 50 for the last 50 lines, --since "1 hour ago" to filter by time.
Q8. What is the difference between df and du?: df shows free/used space per mounted filesystem; du shows how much space specific files or directories use.