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Top 20 Nagios Interview Questions and Answers

Published On: June 10, 2024

Nagios Interview Questions and Answers

Nagios is one of the best continuous monitoring tools that helps with faster software deployment. Here we provide the top 20 Nagios interview questions and answers that cover everything from its architecture to plugins. 

Nagios Interview Questions and Answers for Freshers

1. What is Nagios?

In a DevOps culture, Nagios is one of the monitoring tools used for continuous monitoring of systems, apps, services, and business processes, among other things. 

You don’t have to defend the financial impact of an invisible infrastructure outage on your company when you use Nagios.

2. Which port numbers does Nagios utilize for monitoring?

Typically, the Nagios DevOps tool is used for monitoring ports 5666, 5667, and 5668.

3. Which states do Nagios have?

The state types of Nagios are as follows:

  • Type of service or host state
  • Certain states of the host or service, such as OK, WARNING, UP, or DOWN
  • There are two types of states: hard states and soft states.

4. Define soft state in Nagios.

When the SOFT state is present, the host or service check results are either unacceptable or subpar. Soft Recovery is the process of recovering a component from a Soft error.

Even if the service check has not been performed, the number of times indicated using the max_check_attempts directive is in addition to the times specified for it. 

5. Explain the hard state in Nagios.

Hard errors are those that occur when a host or service check result is not “OK” after the number of checks indicated by the max_check_attempts directive in the host specification. Hard recovery is the process of recovering any service from this problem. 

6. What makes Nagios object-oriented?

You can build object definitions in Nagios’ object configuration format, which allows them to inherit properties from other hostnames or object definitions. The Nagios consider the components as objects.

7. Differentiate between a passive and an active check.

The primary distinction between passive and active checks is that external apps carry out passive checks, whereas Nagios initiates active checks.

8. What does Nagios’ backend mean?

Logs and configuration can both be kept in the backend. NagiosQL is used in the backend to store configurations. NDoutils are used to store historical data. You also have opdb and nagdb in addition.

9. What is Icinga? How is it related to Nagios?

Another well-known open-source program that aids in service monitoring is Icinga. Created in 2009 to support Nagios, it is now a stand-alone piece of software.

10. Explain OID Nagios

Management Information Base definitions for the Simple Network Management Protocol, or SNMP, are done using object identifiers.

11. What is Nagios XI?

The most reliable and potent monitoring program is Nagios. You can use it to monitor metrics, systems, services, network protocols, applications, and systems. It offers you every benefit of Nagios (as mentioned above) and performs exceptionally well.

12. What distinguishes Nagiosxi from Nagios Core?

  • Nagios Core is a free version, while Nagios XI is a paid version.
  • Numerous features of NagiosXI are modifiable via the web interface. 
  • Nagios Core does not include all of the features we require to install plugins to achieve certain tasks.

13. Is it possible to monitor the window machine using Nagios?

You may use Nagios to keep an eye on the window machine by doing the following steps:

  • Configure Nagios to keep an eye on the window system.
  • Set up a different host and server for the window surveillance.

Nagios Interview Questions and Answers for Experienced

14. List the tasks that the Nagios DevOps tool is capable of accomplishing.

  • Automated resolution of issues as they arise.
  • Planning for infrastructure changes begins even before an antiquated system fails.
  • Coordination of technical team responses.
  • To monitor the complete infrastructure as well as the business process.
  • To handle issues as soon as they come up.

15. How does Nagios work?

  • Nagios operates as a daemon or a service on a server. 
  • Nagios oversees plugins located on the same server.
  • They establish contact with hosts or servers within your network or online. 
  • The web interface allows us to check the status, and when something happens, we may also receive email or SMS notifications.
  • The Nagios service functions as a scheduler by executing specific scripts at predetermined intervals. 
  • When a script’s outcome changes, it can save it and execute new scripts.

16. Describe the Nagios plugins.

  • Plugins are essentially Perl and Shell scripts that can be executed via the command line to verify the host’s service status. 
  • Nagios can also make use of the output from the plugins that determine the host’s or network services’ present condition.
  • In response to the topic of why we need plugins, let me also mention that Nagios uses plugins to monitor the health of any host or service. 
  • The plugin runs a check and sends back the results to Nagios. Nagios processes the result and performs the required steps.

17. How is the Nagios configuration verified?

Use the -v command line option to launch Nagios and confirm your configuration as follows:

/usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg

  • If you have misconfigured something or have overlooked entering some crucial data, Nagios will provide a warning or error message that should help you identify the issue. 
  • The line in the configuration file that appears to be the problem’s cause is typically printed out in error messages. 
  • When Nagios encounters an issue, it frequently exits the pre-flight check and returns to the command line, merely printing the fault that it found.

18. Is Nagios able to monitor PostgreSQL and MySQL databases?

With the right plugins, Nagios can monitor databases like PostgreSQL and MySQL. These plugins perform checks on query execution, database connectivity, and other metrics specific to the database. 

19. How do you manage duplicate setups for monitoring in Nagios?

You can split the load among several monitoring instances in Nagios to manage redundancy. If one instance fails, load balancers can route traffic to the remaining instances, guaranteeing monitoring availability.

20. How can the Nagios web interface’s design and layout be customized?

By making changes to the appropriate CSS and HTML files, one can alter the look and feel of the Nagios online interface. This enables you to customize the interface to match the branding and preferences of your company.

21. What does Nagios Remote Plugin Executor, or NRPE, stand for?

You can run Nagios plugins on remote Linux/Unix workstations by using the NRPE addon. 

This is primarily done to enable Nagios to keep an eye on “local” resources (such as CPU load, memory use, etc.) on distant computers. 

These public resources are usually not available from other computers; hence, on remote Linux/Unix PCs, an agent such as NRPE must be installed.

There are two components to the NRPE addon:

  • The local monitoring machine is home to the check_nrpe plugin.
  • The remote Linux/Unix system is home to the NRPE daemon.

22. Which three factors are the primary determinants of inheritance and recursion in Nagios?

After naming the variables, provide a brief description of each one:

Name: Other items utilize it as a placeholder.

Use: It specifies which properties belong to the “parent” object.

Register: This can have a value of 1 (an actual object) or 0 (just a template). One never inherits the register value.


We hope these Nagios interview questions and answers give you expertise and confidence for DevOps interviews. Fine-tune your skills by enrolling in our Nagios training in Chennai.

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