Stage 4: System Champion
Teach learners how to configure and manage networking, firewalls, and services in Linux. Build confidence in handling connectivity, securing systems, and managing active services - skills often tested in DevOps and SysAdmin interviews.
Hackbook Overview
- Networking Basics: Commands like
ifconfig,ip addr,ping,netstat,ss. - Firewall Management: Tools like
iptablesandfirewalldfor controlling traffic. - Service Management: Start, stop, restart, and enable services using
systemctl. - Logs & Monitoring: Use
journalctland/var/log/to troubleshoot services. - Why It Matters: Networking and service management are core to system reliability and security.
Hands‑On Practice
- Check IP address:
ip addr show. - Test connectivity:
ping google.com. - View listening ports:
ss -tuln. - Allow HTTP traffic with firewall:
sudo firewall-cmd --add-service=http. - Restart a service:
sudo systemctl restart nginx. - Check logs:
journalctl -u nginx.
Interview Question Bank
Conceptual
- Q1. How do you check the IP address of a Linux system?
A1. Useip addr showorifconfig(if installed). - Q2. What is the purpose of a firewall in Linux?
A2. A firewall controls incoming and outgoing traffic, protecting the system from unauthorized access. - Q3. What’s the difference between
iptablesandfirewalld?
A3.iptablesis a traditional firewall tool, whilefirewalldprovides a dynamic, easier‑to‑use interface for managing firewall rules.
Practical
- Q4. How do you check if a service is running?
A4. Runsystemctl status <service>. Example:systemctl status ssh. - Q5. How do you open port 80 for HTTP traffic?
A5. Withfirewalld:sudo firewall-cmd --add-service=http. Withiptables:sudo iptables -A INPUT -p tcp --dport 80 -j ACCEPT. - Q6. How do you see which ports are currently open?
A6. Runss -tulnornetstat -tuln.
Scenario‑Based
- Q7. A web server is not accessible. What steps would you take?
A7. Check service status (systemctl status nginx), verify firewall rules (firewall-cmd --list-all), and test connectivity (pingorcurl). - Q8. You need to ensure a service starts automatically on boot. How do you do it?
A8. Runsudo systemctl enable <service>. - Q9. A port is blocked by firewall rules. How do you troubleshoot?
A9. List rules withiptables -Lorfirewall-cmd --list-all, then adjust rules to allow the required port.
Behavioral Based
- Q10. Tell me about a time you solved a networking or service issue.
A10. Example: “I once fixed a production outage by identifying blocked HTTP traffic in firewall rules and reopening port 80.”
Cheatsheet (Quick Notes)
- Networking:
ip addr,ping,ss -tuln. - Firewall:
iptables,firewalld. - Services:
systemctl start|stop|restart|enable <service>. - Logs:
journalctl -u <service>,/var/log/.
Updated on Dec 21, 2025