1. What is Nagios?
A) Nagios is an open-source monitoring tool used to monitor servers, network devices, applications, and services. It alerts administrators about system issues before they become critical.
2. What are the key features of Nagios?
A)
- Monitoring of hosts, services, and networks.
- Alerting via email, SMS, or scripts.
- Performance graphing (with plugins like PNP4Nagios).
- Web-based GUI for monitoring status.
- Support for event handlers and plugins.
3. What are Nagios Plugins?
A) Plugins are scripts or executables used by Nagios to check the status of services, hosts, or applications. They return status codes like OK, WARNING, CRITICAL, or UNKNOWN.
4. What are the main components of Nagios architecture?
A)
- Nagios Core (engine).
- Plugins (checks).
- Add-ons (NRPE, PNP4Nagios, etc.).
Web Interface.
5. What is NRPE in Nagios?
A) NRPE (Nagios Remote Plugin Executor) allows Nagios to execute plugins on remote Linux/Unix machines.
6. What is the difference between active and passive checks in Nagios?
A)
- Active checks: Initiated by the Nagios server at scheduled intervals.
- Passive checks: Results sent to Nagios by external applications or scripts.
7. What is an event handler in Nagios?
A) An event handler is a script that Nagios executes automatically when a host or service changes state (e.g., restart a service when it fails).
8. What is the purpose of Nagios configuration files?
A) They define objects like hosts, services, contacts, groups, commands, and time periods. Key config files: nagios.cfg, objects/commands.cfg, objects/services.cfg.
9. How does Nagios notify administrators about issues?
A) Nagios sends notifications via email, SMS, or custom scripts defined in the notification configuration.
10. How do you check Nagios logs?
A) Nagios logs are stored in:
/usr/local/nagios/var/nagios.log
11. How do you verify Nagios configuration?
A) Run:
nagios -v /usr/local/nagios/etc/nagios.cfg
12. What is the purpose of check_by_ssh plugin in Nagios?
A) It allows Nagios to run checks on remote hosts using SSH without requiring NRPE.
13. How do you schedule downtime in Nagios?
A) Downtime can be scheduled via the web interface or by using commands to suppress alerts during planned maintenance.