Nagios Interview Questions and Answers




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Top Nagios Interview Questions and Answers - 2021 [UPDATED]

Are you looking for Nagios Interview Questions and Answers? Than you are at the Right Place. Browse through Popular and Most Asked Interview Questions for Nagios.  There is a Huge Demand for Nagios Professionals in the Market. These Questions are suitable for both Freshers and Experienced Professionals and are based on Trending Topics and as per Current Industry Requirements.

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Nagios Interview Questions and Answers

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Nagios commonly known as the Nagios core is the open-source software that is designed to monitor networks, systems, applications, and infrastructures. The software directly sends the track down all the changes in the subject and send alerts if necessary.

Nagios was designed in the first place to monitor applications, networks, and infrastructures. The software automatically keeps an eagle eye and immediately report in case of failure. The quick response helps the DevOps professional to track down and resolve the problem in the early stages before it can cause any serious damage to the organization.

The below features of the Nagios is what makes it an ideal tool for continuous monitoring: Automatic problem fixing Infrastructure upgrades Business process and infrastructure monitoring Quick respond to the system issues

When you are using the Nagios to monitor the Linux environment then you need to understand that you are using one of the best tools on the planet. The complete package of Nagios includes service state, file system usage, system metrics, process state, and more.

Icinga is also an open-source software that is used to monitor the networks and applications. The core objective of designing Icinga in the first place to lift up the Nagios back in 2009. But it works as a separate monitor software.

In the Nagios, an active check is leveraged to “poll” a service or device for the status information every once in a while. Nagios basically supports the way to host down the devices and services passively. The key feature of the passive check is it can only be performed by the external applications.

Simple Network Management Protocol (SNMP)- a network protocol that is also designed for the monitoring purpose uses the Object Identifiers to define the Management Information Base.

Yes, you can use Nagios to monitor the window machine. However, if you are doing it for the first time then you have to follow the given steps: Set the Nagios to monitor the window system Add a separate host and server for the window monitoring

On the current basis, Nagios XI is one of the most powerful monitoring software in the market. when it comes to monitoring critical infrastructures such as network protocols, applications, services, systems metrics, and network protocols experts only rely upon the Nagios XI.

There are various benefits of using Nagios software for critical monitoring. The list of benefits includes: Infrastructure updates before the outdated system cause any sort of failure Automatic tracking and troubleshooting of problem Coordinate responses Continuously Monitor infrastructure without any break Response to issues on an immediate basis

Active check is the globally recognized way to monitor the hosts and services. Both Nagios XI and Nagios core use it on the pre-determined schedule.

A network analyzer is a crucial aspect of the Nagios software that allows it to deeply scan the entire system in a search of any potential threat. The quick and reliable scan allows system admin to gather necessary data regarding the health of the system and granular data through network analysis.

The key benefits of monitoring websites with Nagios are given below: It enhances the website availability Increase website performance Quick detection of online threats such as bugs and hijacking

There are a number of databases that support Nagios and some of them are mentioned below: Oracle MySQL Microsoft SQL software Postgres

Nagios supports the number of protocols monitoring including; SMTP Monitoring, IPMI Monitoring, FTP Monitoring, LDAP Monitoring, POP Monitoring, and DNS monitoring.

As already mentioned above, Nagios is open-source object-oriented monitoring software. Here the term “object-oriented” means that users can create the object definitions in the Nagios that inheritance from other objects. This essential feature of the Nagios further simplifies the complex relationship between components.

Yes, Nagios has a reputation as one of the best monitoring software in the market and you can use it for various monitoring purposes including both virtual and physical.

VMware, Amazon EC2, Xen and Microsoft Virtual PC are some of the most common examples of the virtualization platforms that support the Nagios monitoring.

Yes, the Nagios uses port number; 5666, 5667 and 5668 to monitor its clients.

If you want to configure the Nagios, then you have to run it with the -v command line with option like: nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg.

In the Nagios, objects refer to all the elements that are involved in the entire monitoring and alerting logic.

The types of objects you can witness in the Nagios include; Services, Hosts, commands, host groups, contact, time periods, and notification escalations.

Just like any other plugin, you have to download plugin X from the official website of Nagios which is Once downloaded, you can run it manually to see if it is working correctly.

Well, when it comes to monetary terms, Nagios Core is the free open source version while Nagios XI is the paid version limited to the individual who held the license.

On the current basis, the monitoring host and services are determined by the two major components First: Status of the host and service Second: Types of the state the host or service is in

The Nagios have two key state types; soft states and hard states.

The term NRPE stands for the Nagios Remote Plugin Executor addon which is specifically designed by the experts to execute Nagios plugins on the Linux machines.

RRD is the database format Nagios support and uses to store the status data.

The NDO utilities are the right mixture of the: NDOMOD Event Broker Module FILE2SOCK Utility LOG2NDO Utility NDO2DB Daemon

Yes, you can monitor any operation system through Nagios as long as it supports the software.

PHP+CGI, Requires Apache as webserver to run php and cgi

User and Password : nagiosadmin

Location is /usr/lib64/nagios/plugins

Consider the following definition define host{ name linux-box use generic-host check_command check-host-alive } Here in the line “use generic-host” is the concept of inheritance as it will grab all the properties of generic-host which is already defined in templates.cfg

Use cfg_dir=”Directory Location” so that it will consider all configuration under that directory.

In nrpe configuration, do the following allow_hosts=”nagios server ip” dont_blame_nrpe=1 Allow port 5666 in firewall of nrpe agent

0 – OK, 1 – WARN, 2 – CRITICAL, 3 – UNKNOWN

Passive monitoring can be used. Data for monitoring is being collected and stored in to passive poll store from where Nagios can pickup and display.

SSH, HTTP, FTP, SMTP, Disk Usage, Memory Usage, Network status etc.

We need to write a custom plugin script(Bash/Python) which in turn get the status of each and every load average of servers, and then get average of those values.

We need to configure aws-cli with required privileges and we have to write custom plugin for the required service to be monitored.

We have to create custom Event Handler to achieve this. URL :

URL a) Write a bash script in following format. #!/bin/bash # Nagios Plugin Bash Script - # This script checks if program is running # Check for missing parameters if [[ -z "$1" ]] thenecho "Missing parameters! Syntax: ./ service_name"exit 3 fi if ps ax | grep -v grep | grep $1 > /dev/null then echo "OK, $SERVICE service is running"exit 0 else echo "CRITICAL , $SERVICE service is not running" exit 2 fi b) Save the above script in a file and move to the Nagios Plugings Location. c) Change permission of the script to 755 d) Write a command definition in command.cfg e) Use this command definition in other service definitions.

We have to install NSClient++ nagios client application in the windows server, then configure it for allowing required plugins. URL : ; Undocumented key CheckDisk = enabled ; Undocumented key CheckSystem = enabled Test as nagios server side : /usr/lib/nagios/plugins/check_nt -H HOSTNAME -p 12489 -s PASSWORD -v CPULOAD -l 5,80,90

This is NSClient++ client port for monitoring windows servers.

/usr/local/nagios/libexec/check_nrpe -H nrpe-agent -c check_disk -a ‘-w 20% -c 10%’ Replace nrpe-agent with the server hostname -c is command to check -a is for arguments

USER1 is a macro in nagios which will expand to the plugin location in the command. Nagios supports up to 256 user macros ($USER1$ through $USER256$). Eg: $USER1$/check_load is /usr/lib64/nagios/plugins/check_load Ref:

HOSTADDRESS is the Address of the host. This value is taken from the address directive in the host definition. HOSTALIAS is the Long name/description for the host. This value is taken from the alias directive in the host definition.

OCSP is Obsessive Compulsive Service Processor Command which allows you to specify a command to be run after every service check, which can be useful in distributed monitoring. This command is executed after any event handler. or notification commands.

1. Enable the process_performance_data option. Example: process_performance_data=1 in Service definition. 2. Configure Nagios so that performance data is either written to files and/or processed by executing commands. Example: define command { command_name store-service-perfdata command_line /bin/echo -e "$LASTSERVICECHECK$\t$HOSTNAME$\t$SERVICEDESC$\t$SERVICESTATE$ \t$SERVICEATTEMPT$\t$SERVICESTATETYPE$\t$SERVICEEXECUTIONTIME$\ t$SERVICELATENCY$\ t$SERVICEOUTPUT$\t$SERVICEPERFDATA$" >> /usr/local/nagios/var/service-perfdata.dat }