Nagios Interview Questions and Answers

Nagios Interview Questions and Answers

Last updated on 23rd Oct 2020, Blog, Interview Question

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Are you a software professional striving for a successful career? Do you want to be a member of Nagios family? ACTE show you the platform for your growing career. Nagios is an open source software application that offers to monitor and alert services for applications and servers. Nagios provides enterprise-class IT infrastructure monitoring, applications monitoring and network monitoring. Nagios admin job needs experience in a scripting language, implementing Nagios core, knowledge of Linux system related commands and should be able to work independently as well as team player. Many standard IT organizations offer different roles for Nagios admin jobs such as Team lead, NOC engineer, system admin and network engineer etc in prominent cities of India. 

1. what is Nagios?


Nagios is a monitoring tool that is used for continuous monitoring of system services, applications, and business processes. Even in case of any failure, Nagios tool can alert the technical staff about the problem. As a result, DevOps professionals or technical team members can begin the required remediation processes before the negative impact of any business processes, customers, and end-users. Here, in such cases, the team does not have to explain anyone that why an unseen infrastructure outage affects the bottom line of the organization.

2.Mention the things that can be achieved by the Nagios DevOps tool?


  • Automatic problem fixing as and when they occur.
  • Infrastructure upgrades planning even before any failure due to an outdated system.
  • Technical team response coordination.
  • To ensure that SLA of your organization will be met.
  • To monitor the business process and the entire infrastructure.
  • To respond to issues even as and when they arise.

3.Explain the working of Nagios, how does it work?


  • On a server, Nagios either runs as a service or daemon. Plugins that reside on the same server are being run by the Nagios; basically, they contact the hosts or servers of your network or on the internet. We can check the status by web interface; even notifications can also be received by email or SMS when something happens.
  • Nagios service runs certain scripts after a fixed time interval, so it acts as a scheduler. It can store the script result and run other scripts when it is changed.

4. Explain Nagios plugins?


  • Plugins are basically scripts of Perl and Shell that can be run through the command line to check the service status of the host. Nagios can also use the result of the plugins that determine the present status of host or services of the network.
  • Now an answer to the questions that why we need plugins, you can also add here that, plugins is executed by Nagios to check the status of any service or host. A check is performed by the plugin and the result is returned to Nagios. The result is processed by Nagios to take the necessary actions.

5. What do you understand by NRPE or Nagios Remote Plugin Executor of Nagios?


NRPE or Nagios remote plugin executor is designed to allow execution of plugins on remote Linux or UNIX based machines. These plugins are executed to monitor the usage of CPU load and memory usage like a local resource of remote machines. It is required as this information is not usually exposed publicly to an external machine and for this purpose, NRPE agent is installed on remote machines.

NRPE add-on or plugin has two components that work together to perform the task:

  • A ‘check_nrpe’ plugin that resides on the local machine and it is used for monitoring
  • The NRPE daemon that can run on remote machines

6. What are port numbers used by Nagios for monitoring purpose?


Usually, the port number 5666, 5667 and 5668 are used for monitoring in Nagios DevOps tool.

7. Explain main configuration file and its location?


Following is the description of the main configuration file:

  • Resource File: To store sensitive information like user details that may include username and passwords it is used. The information is not made available to CGI.
  • Object Definition File:  In this file, you can find and enlist the details of resources that you want to monitor and how you want the monitoring to be performed? Host services, host groups, contacts, contact groups, commands, etc. are defined in this file.
  • CGI Configuration File: Several directives are contained and stored in CGI file that can affect the CGI o. A reference to the main configuration file is also stored in this file, so that CGI can know the details of Nagios configuration as and when required and the location of object definition storage.

8. What are state types of Nagios?


Following are the state types of Nagios:

  • Service or host state type
  • Some states like OK, WARNING, UP, or DOWN state host or service
  • Two state types that are SOFT state or HARD state

9.What are SOFT and HARD states?


We can define soft and hard states as:

  • In case of the SOFT state, the service or host check results are not OK or not up to the mark, even in case if service check has not been rechecked the number of times that are specified for it moreover the times that is being specified by the max_check_attempts directive. Recovery of the component from such Soft error is called Soft Recovery.
  • When a host or service check result is not ‘OK’ and it has been checked for the number of times, specified by the max_check_attempts directive in the host definition, then this error is known as Hard Error. Recovery of any service from this error is known as Hard Recovery.

10. What is state stalking in Nagios?


  • State stalking is used for logging purpose in Nagios. When stalking is enabled for any service or host then Nagios watch it very carefully and store any changes that if found in the check result of that resource.
  • Stalking can be helpful in later stages of log file analysis. Here in such scenario, any host or service check can be performed only if it has been updated for the last time.

11.Why is it being said that Nagios is object oriented?


Nagios has object configuration format where you can create object definitions, that can inherit the properties from other hostnames or object definitions. In this way, you can specify the component relationships easily. The components are considered as objects by the Nagios.

12.Which three Nagios variables can affect recursion and inheritance in Nagios?


The three variables that affect recursion and inheritance are:

  • Name
  • Use
  • Register

Here, Name is just a placeholder that can be used by the other objects. Use variable can be used to define parent object, whose properties are to be used. Registers are also used for storing values that can be either 0 or 1. Register values cannot be inherited.

13.How Does Flap detection work in Nagios?


When a service or host changes their state frequently, then it is called flapping that may cause lots of problems and generate too many recovery notifications.

Flapping is detected in the following manner:

  • Store the results of last 21 checks and then analyze this historical check result to know the number of transitions that are being taken place by the host or service.
  • Know the percent state change value with the help of state transition
  • Compare the value of this state change against low and high flapping thresholds
  • When this value exceeds then the highest specified threshold then it is called flapping
  • When this percent state value goes down the specified value then it is said that flapping has been stopped.

14.Explain main configuration file of Nagios?


  • Several directives are contained in the main configuration file that can affect Nagios daemon. This file is read by both CGIs and Nagios daemons.
  • A Nagios file is usually created in the base Nagios directory, at the time when you run configuration script. The name of this file that is the main configuration file is ‘nagios.cfg’ and is usually placed in etc/subdirectory
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15.How is distributed monitoring being done in Nagios?


There is a distributed monitoring scheme in Nagios with the help of which you can monitor your complete enterprise that may include local slave instances. In such environment, Nagios submit the result of reports of tasks to a single machine. All configuration, reporting, and notification can be managed at the master machine and here slaves do all the work. Here Nagios uses passive checks that are basically external applications that can send the results back to Nagios.

16.Differentiate between active and passive check?


The major difference between active and passive check is that Active checks are initiated by Nagios itself, while Passive checks are performed by external applications.

17.What are the important features of nagios?


MonitoringIts powerful script APIs allow easy monitoring of in-house and custom applications, services, and systems
Visibility & AwarenessIt provides a centralized view of the entire monitored IT infrastructure with detailed status information
Problem RemediationAlert acknowledgments in Nagios, provide communication on known issues and problem response
Proactive PlanningTrending and capacity planning add-ons are there in Nagios to aware you about  the aging infrastructure
ReportingAvailability reports ensure SLAs are being met & provide a record of alerts, notifications, and alert response
CustomizableCodeSince it is an open source software you get the full access to its source code
Large CommunityNagios is backed up by a community of more than 1 million+ users worldwide which provides free support

18. How does Nagios work?


  • Nagios runs on a server, usually as a daemon or service.
  • Nagios periodically runs plugins residing on the same server, they contact hosts or servers on your network or on the internet.
  • One can view the status information using the web interface.
  • You can also receive email or SMS notifications if something happens.
  • The Nagios daemon behaves like a scheduler that runs certain scripts at certain moments.
  • It stores the results of those scripts and will run other scripts if these results change.

19.What is meant by Nagios backend?


Both Configuration and Logs can be stored in a backend. Configurations are stored in backend using NagiosQL. Historical data are stored using ndoutils. In addition, you also have nagdb and opdb.

20.When Does Nagios Check for external commands?


Nagios check for external commands under the following conditions:

  • At regular intervals specified by the command_check_interval option in the main configuration file or,
  • Immediately after event handlers are executed. This is in addition to the regular cycle of external command checks and is done to provide immediate action if an event handler submits commands to Nagios.

21.How does Nagios help with Distributed Monitoring?


With Nagios you can monitor your whole enterprise by using a distributed monitoring scheme in which local slave instances of Nagios perform monitoring tasks and report the results back to a single master. You manage all configuration, notification, and reporting from the master, while the slaves do all the work. This design takes advantage of Nagios’s ability to utilize passive checks i.e. external applications or processes that send results back to Nagios. In a distributed configuration, these external applications are other instances of Nagios.

22.Explain how Flap Detection works in Nagios?


Flapping occurs when a service or host changes state too frequently, this causes lot of problem and recovery notifications.Whenever Nagios checks the status of a host or service, it will check to see if it has started or stopped flapping.

Nagios follow the below procedure to do that:

  • Storing the results of the last 21 checks of the host or service analyzing the historical check results and determine where state changes/transitions occur.
  • Using the state transitions to determine a percent state change value (a measure of change) for the host or service.
  • Comparing the percent state change value against low and high flapping thresholds
  • A host or service is determined to have started flapping when its percent state change first exceeds a high flapping threshold.
  • A host or service is determined to have stopped flapping when its percent state goes below a low flapping threshold.

23.What is meant by saying Nagios is Object Oriented?


One of the features of Nagios is object configuration format in that you can create object definitions that inherit properties from other object definitions and hence the name. This simplifies and clarifies relationships between various components.

24.Nagios says my machine is unreachable, not down. What is the difference and how it is achieved?


When Nagios says a node is unreachable, a node is unreachable if Nagios is not able to find a path to the node.

The node itself may be up but because Nagios is unable to connect to it, it has to mark this as unreachable. To achieve this, Nagios use parent-child relationship between components.A router may be defined as a parent for a server.

  • Now Nagios checks for server and marks it as down.
  • It then checks the parent (in our example, the router)
  • If parent is also down, then server is marked as unreachable.
  • If Parent is up, the server is marked as really down.

25.Explain Nagios state types?


The current state of monitored services and hosts is determined by two components:

  • The status of service or host i.e. OK, WARNING, UP, DOWN etc..
  • The type of state the service or host is in.

There are two types of states SOFT states and HARD states.

  • When a service or host check results are in a non-OK or non-UP state and the service check has not yet been rechecked the number of times specified by the max_check_attempts directives in the service or host definition. This is called Soft Error. When a service or a host recovers from Soft Error that is considered as Soft Recovery.
  • When a service or host check results are in a non-OK or non-UP state and the service check has been rechecked the number of times specified by the max_check_attempts directives in the service or host definition. This is called Hard Error. When a service or a host recovers from Hard Error that is considered as Hard Recovery.

26.How does Nagios operate?


  • Nagios runs as a service on a server
  • It runs plugins on the server which connect with hosts on the network
  • You can see the detailed information of the connected host through its interface
  • In case some issue arises, you would receive an email or another notification
  • Nagios runs scripts at specific times and saves the results of those scripts
  • If the results of running the scripts change, Nagios starts running other scripts

27.What is a Passive Check? 


In Nagios, external processes initiate Passive checks. When they are completed, the results are sent to Nagios. Passive checks help in monitoring asynchronous services. Those services can’t be tracked without regular polling of their status. Passive checks also help Nagios in checking the status of hosts that are behind a firewall as they can’t be verified through a monitoring host. 

28.What are the advantages of using Nagios?


Nagios offers plenty of advantages to an organization. 

  • It allows you to plan future upgrades for your existing infrastructure
  • It ensures a technical error in your IT infrastructure has minimum impact
  • It quickly alerts you of any new problems
  • It allows you to monitor the entire system and infrastructure 
  • It coordinates the responses of the technical staff
  • It helps you find out how fast your team responds to technical problems
  • It ensures that SLAs (Service-Level Agreements) of your organization are met

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


Icinga is another popular open-source software that helps in monitoring services. It was designed in 2009 to help Nagios, but it has become a separate software. 

30.What is an Active Check?


Nagios performs an Active check to poll a device or service for its status information on a scheduled basis. 

31.Can you name a few databases which support Nagios?


Many databases support Nagios. They are Oracle, Postgres, Microsoft SQL solutions, and MySQL. 

32.What is Nagios XI?


Nagios is the most trusted and most powerful monitoring software. It can help you in monitoring applications, network protocols, systems, services, and metrics. It provides you with all the advantages of Nagios (discussed above) and has a powerful performance. 

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33.Is Nagios used to monitor window machines?


Yes, Nagios is used to monitor window machines. You can do so by setting-up Nagios for monitoring the required window system and then add a separate server and host for performing the task. 

34.What is OID Nagios?


The Simple Network Management Protocol (aka SNMP) uses Object Identifiers for defining the Management Information Base. 

35.What is the Nagios Network Analyzer?


The network analyzer is a vital component of Nagios which checks the system for potential dangers. Its quick scan enables the admin to get the required data about the health of the system. 

36.Is Nagios Object-oriented? If so, can you elaborate on what it means?


Object-oriented means that you can produce object definitions in Nagios that are inherited from other objects. As Nagios is object-oriented, its relationship with its components remains simple without any intricate details. 

37.Which protocols support Nagios?


SMTP Monitoring, POP Monitoring, FTP Monitoring, IPMI Monitoring, DNS Monitoring, and LDAP Monitoring are some of the protocols Nagios supports. 

38.Can you use Nagios for Cloud Monitoring?


Yes, you can use Nagios for cloud monitoring. It is one of the most popular monitoring tools available in the market. 

39.What are objects in Nagios?


All elements related to the alerting logic and the monitoring process are objects in Nagios. 

40.Name three virtualization platforms that support Nagios?


Microsoft Virtual PC, Amazon EC2, and VMware are three of the most popular 

virtualization platforms supporting Nagios. 

41.What are the object types in Nagios?


Nagios has a variety of object types such as host groups, periods, services, hosts, contact, notifications, and commands. 

42.What are the two-state types in Nagios?


Soft states and hard states are the two primary state types in Nagios. 

43.Which database format does Nagios support for storing data?


Nagios supports the RRD database format for storing status data. 

44.What are the sections of NDO utilities?


NDO utilities include FILE2STOCK Utility, NDOMOD Event Broker Module, NDO2DB Daemon, and LOG2NDO Utility. 

45.What are the default credentials in Nagios?


The Username and Password are “nagiosadmin” in Nagios as default. 

46.What language does Nagios core use?


Nagios core uses PHP and CGI. 

47.What are the required conditions for Nagios to check external commands?


Nagios checks for external commands regularly according to the command_check_interval option. In addition to the regular checks, it also checks for external commands when an event handler is executed. 

48.How is Nagios related to DevOps?


Continuous monitoring is a core component of DevOps and Nagios is a popular tool for the same. 

49.Can you customize charts in Nagios?


Yes, you can customize charts through a third-party tool such as Graphite or CACTI.

50.Explain The Need For Passive Check?


Passive checks are useful for monitoring services that are Asynchronous in nature and cannot be monitored effectively by polling their status on a regularly scheduled basis. It can also be used for monitoring services that are Located behind a firewall and cannot be checked actively from the monitoring host.

51.Explain the Main Configuration file of Nagios and its location?


The main configuration file contains a number of directives that affect how the Nagios daemon operates. This config file is read by both the Nagios daemon and the CGIs.A sample main configuration file is created in the base directory of the Nagios distribution when you run the configure script. The default name of the main configuration file is nagios.cfg, it is usually placed in the, etc/ subdirectory of you Nagios installation.

52.How To Generate Performance Graphs?


 In Nagios Core, there is no inbuilt option to generate the performance graphs, We have to install pnp4nagios and add hosts and services URL’s in definition files.

53.How To Verify Nagios Configuration?


In order to verify your configuration, run Nagios with the -v command-line option like so:

If you’ve forgotten to enter some critical data or misconfigured things, Nagios will spit out a warning or error message that should point you to the location of the problem. Error messages generally print out the line in the configuration file that seems to be the source of the problem. On errors, Nagios will often exit the pre-flight check and return to the command prompt after printing only the first error that it has encountered.

54.What is Nagios monitoring tool in Linux?


Nagios provides complete monitoring of Linux operating systems and distributions – including operating system metrics, service state, process state, file system usage, and more. When you use Nagios to monitor your Linux environment, you’re using one of the most powerful Linux monitoring tools on the planet.

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55. What does Nagios use to monitor?


Nagios is now known as Nagios Core, is a free and open source computer-software application that monitors systems, networks and infrastructure. Nagios offers monitoring and alerting services for servers, switches, applications and services.

56. What does Check_mk do?


Check_MK is an extension to the Nagios monitoring system that allows creating rule-based configuration using Python and offloading work from the Nagios core to make it scale better, allowing more systems to be monitored from a single Nagios server.

57. What is icinga2?


Icinga 2 is an open source monitoring system which checks the availability of your network resources, notifies users of outages, and generates performance data for reporting. Scalable and extensible, Icinga 2 can monitor large, complex environments across multiple locations.

58. Can Nagios monitor Windows machine?


To monitor Windows Machines you will need to follow several steps and they are: Install NSClient++ addon on the Windows Machine. Configure Nagios Server for monitoring Windows Machine. Add new host and service definitions for Windows machine monitoring.

59. What is Nrpe in Nagios?


NRPE allows you to remotely execute Nagios plugins on other Linux/Unix machines. This allows you to monitor remote machine metrics (disk usage, CPU load, etc.). NRPE can also communicate with some of the Windows agent addons, so you can execute scripts and check metrics on remote Windows machines as well.

60. What is Nagios Log Server?


Nagios Log Server greatly simplifies the process of searching your log data. Set up alerts to notify you when potential threats arise, or simply query your log data to quickly audit any system. With Nagios Log Server, you get all of your log data in one location, with high availability and fail-over built right in.

61. What is Nagios Network Analyzer?


Nagios Network Analyzer provides an in-depth look at all network traffic sources and potential security threats allowing system admins to quickly gather high-level information regarding the health of the network as well as highly granular data for complete and thorough network analysis using netflow, sflow, jflow, etc.

62. Explain the process of website Monitoring With Nagios?


Nagios provides complete monitoring of websites, web applications, web transactions, and web services – including availability, URL monitoring, HTTP status, content monitoring, hijack detection, and more.

63.What are the benefits of website monitoring with Nagios?


Implementing effective website monitoring with Nagios offers the following benefits:

  • Increased website and web application availability
  • Increased website performance
  • Fast detection of outages, website defacement, and website hijacking
  • Capacity planning information for future web server and application upgrades

64. What are the benefits of HTTP monitoring with Nagios?


Nagios provides complete monitoring of HTTP and HTTPS servers and protocols.Benefits – Implementing effective HTTP monitoring with Nagios offers the following benefits:

  • Increased server, services, and application availability
  • Fast detection of network outages and protocol failures
  • User experience monitoring
  • Web server performance monitoring
  • Web transaction monitoring
  • URL monitoring

65. What are the benefits of SSL Certificate Monitoring With Nagios?


Nagios provides SSL Certificate monitoring to ensure that expired certificates don’t negatively impact your organization’s websites, applications, and security.Benefits – Implementing effective SSL Certificate monitoring with Nagios offers the following benefits:

  • Increased website and application availability
  • Increased security

66. What are the benefits of Database Monitoring with Nagios?


Nagios provides complete monitoring of database servers and databases – including availability, database and table sizes, cache ratios, and other key metrics.Benefits – Implementing effective database monitoring with Nagios offers the following benefits:

  • Increased application availability
  • Increased database performance
  • Fast detection of database outages, failures, and table corruption
  • Predictive analysis of storage requirements and index performance

67. Which databases supports Nagios?


Nagios supports following databases for monitoring.

  • MySQL
  • Postgres
  • Oracle
  • DB2 Monitoring
  • Microsoft SQL Server

68.What is the difference between soft and hard states in Nagios?


  • When the results of a host or service are not OK, but it has not been rechecked multiple times according to max_check_attempts, then the error is specified as a Soft error. When a host or service recovers from a Soft Error, it is called Soft Recovery.
  • On the other hand, when the results of a host or service check are not OK even when they have been rechecked several times, according to max_check_attempts, the error is called Hard Error. Recovery from such a kind of error is called Hard Recovery. 

69.Which three variables affect inheritance and recursion in Nagios?


The three variables affecting recursion and inheritance are Name, Use, and Register. The name is a placeholder for other objects. Use specifies the parent object and Register can either have a value of 1 or 0. If the Register has a value of 1, it means it’s an actual object. If it has a value of 0, it means the object is only a template and isn’t a real object. 

70.What is Flap Detection in Nagios?


  • When a host or service changes its state too frequently, it is called Flapping. Flapping can lead to many problems, which could, in turn, cause many recovery notifications to arise. Nagios checks if a service or host has started flapping during its status check. 
  • Nagios checks for flapping. It does so by storing the results of the previous 21 checks of the specific service or host first. And it analyzes those results to see how frequent state changes occurred. It determines a percent state change value through that data and compares the same to flapping thresholds. When the percent state change is greater than the high threshold for flapping, the object is said to have started flapping. And when the percent state change is lower than the low threshold for flapping the object is said to have stopped flapping. 
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71.How would  you explain the ‘Machine is Unreachable’ error?


When Nagios fails in finding a path to a specific node, it shows this error. The node might be up, but because Nagios can’t access it, it shows the node as unreachable. 

72. Nagios supports which protocol monitoring?


Nagios supports following Protocol Monitoring:

  • HTTP Monitoring
  • DNS Monitoring
  • FTP Monitoring
  • SNMP Monitoring
  • SMTP Monitoring
  • SSH Monitoring
  • LDAP Monitoring
  • IMAP Monitoring
  • POP Monitoring
  • ICMP Monitoring
  • DHCP Monitoring
  • IPMI Monitoring

73. What are the benefits of Operating System (OS) Monitoring with Nagios?


Nagios provides complete monitoring of desktop and server operating systems – including system metrics, service states, process states, performance counters, event logs, applications (IIS, Exchange, Apache, MySQL, etc), and services (Active Directory, DHCP, Sendmail, etc).Benefits: Implementing effective operating system monitoring with Nagios offers the following benefits:

  • Increased server, services, and application availability
  • Fast detection of network outages and protocol failures
  • Fast detection of failed services, processes and batch jobs

74. Nagios supports which OS Monitoring?


Nagios supports following operating system monitoring:

  • Windows Monitoring
  • Linux Monitoring
  • UNIX Monitoring
  • Solaris Monitoring
  • AIX Monitoring
  • HP-UX Monitoring
  • RHEL Monitoring
  • Ubuntu Monitoring
  • Debian Monitoring
  • CentOS Monitoring
  • Fedora Monitoring
  • SuSE Monitoring

75. What are the benefits of Cloud Computing And Cloud Monitoring With Nagios?


Nagios provides complete monitoring of cloud computing, web, and storage services. Nagios is capable of monitoring a variety of servers and operating systems – both physical and virtual.Benefits – Implementing effective cloud monitoring with Nagios offers the following benefits:

  • Increased server, services, and application availability
  • Fast detection of network outages
  • Fast detection of cloud computing environment problems

76. Explain Virtualization With Nagios?


Nagios provides the capabilities to monitor an assortment of metrics on many different virtualization platforms. In addition, Nagios can be run from several different virtualization platforms such as VMware, Microsoft Virtual PC, Xen, Amazon EC2, etc. Nagios had pre-built VM’s for both Nagios Core and Nagios XI created for VMware, as well as Virtual PC and OFV Template for Nagios XI.Benefits: Implementing effective virtualization monitoring with Nagios offers the following benefits:

  • Increased server, services, and application availability
  • Fast detection of server and operating system failures
  • Fast detection of service and application failures
  • Reduced deployment time
  • Reduced administrative overhead
  • Centralized configuration
  • Ability to monitor the following Metrics

77. Explain Application Server Monitoring With Nagios?


Nagios provides complete monitoring of application servers – including JBOSS, Websphere, Weblogic, ActiveMQ, and Tomcat.Benefits: Implementing effective application server monitoring with Nagios offers the following benefits:

  • Increased server, services, and application availability
  • Fast detection of network outages and protocol failures
  • Fast detection of failed process, services and batch jobs

78. Explain Storage Monitoring With Nagios?


Nagios provides complete monitoring of storage systems – including directory size, disk usage, file count, file presence, file size, S.M.A.R.T. status, RAID array status, and more.Benefits: Implementing effective storage monitoring with Nagios offers the following benefits:

  • Detection of failed batch jobs
  • Advanced planning for system upgrades
  • Fast detection of storage subsystem problems
  • Early detection of potential future failures
  • Reduced risk of unexpected downtime

79. Explain Log Monitoring and Management with Nagios?


Nagios provides complete monitoring and log management of application logs, log files, event logs, service logs, and system logs on Windows servers, Linux servers, and Unix servers. Nagios is capable of monitoring system logs, application logs, log files, and syslog data, and alerting you when a log pattern is detected.Benefits: Implementing effective log monitoring with Nagios offers the following benefits:

  • Increased security
  • Increased awareness of network infrastructure problems
  • Increased server, services, and application availability
  • Fast detection of network outages and protocol failures
  • Fast detection of failed processes, services, cron jobs, and batch jobs
  • Audit compliance and regulatory compliance

80.What Database Is Used By Nagios To Store Collected Status Data?


Nagios core will use default RRD database format to store status data

81. What Are The Operating Systems We Can Monitor Using Nagios?


Any Operating System We can monitor using Nagios, OS should support to install Nagios Client either SNMP.

82. What Are The Components That Make Up The Ndo Utilities ?


There are four main components that make up the NDO utilities:

  • NDOMOD Event Broker Module : The NDO utilities includes a Nagios event broker module (NDOMOD.O) that exports data from the Nagios daemon.Once the module has been loaded by the Nagios daemon, itcan access all of the data and logic present in the running Nagios process.The NDOMOD module has been designed to export configuration data, as well as information about various run time events that occur in the monitoring process, from the Nagios daemon. The module can send this data to a standard file, a Unix domain socket, or a TCP socket.
  • LOG2NDO Utility : The LOG2NDO utility has been designed to allow you to import historical Nagios and NetSaint log files into a database via the NDO2DB daemon (described later). The utility works by sending historical log file data to a standard file, a Unix domain socket, or a TCP socket in a format the NDO2DB daemon understands. The NDO2DB daemon can then be used to process that output and store the historical log file  information in a database.
  • FILE2SOCK Utility :  The FILE2SOCK utility is quite simple. Its reads input from a standard file (or STDIN) and writes all of that data to either a Unix domain socket or TCP socket. The data that is read is not processed in any way before it is sent to the socket.
  • NDO2DB Daemon:   The NDO2DB utility is designed to take the data output from the NDOMOD and LOG2NDO components and store it in a MySQL or PostgreSQL database.When it starts, the NDO2DB daemon creates either a TCP or Unix domain socket and waits for clients to connect. NDO2DB can run either as a standalone, multi-process daemon or under INETD (if using a TCP socket). Multiple clients can connect to the NDO2DB daemon’s socket and transmit data simultaneously. A separate NDO2DB process is spawned to handle each new client that connects. Data is read from each client and stored in a user-specified database for later retrieval and processing.

83. What Is Ndoutils ?


The NDOUTILS addon is designed to store all configuration and event data from Nagios in a database. Storing information from Nagios in a database will allow for quicker retrieval and processing of that data and will help serve as a foundation for the development of a new PHP-based web interface in Nagios 4.1.

84. What Is Nrpe?


The Nagios Remote Plugin Executor addon is designed to allow you to execute Nagios plugins on remote Linux/Unix machines. The main reason for doing this is to allow Nagios to monitor “local” resources (like CPU load, memory usage, etc.) on remote machines. Since these public resources are not usually exposed to external machines, an agent like NRPE must be installed on the remote Linux/Unix machines.

85. Explain Distributed Monitoring ?


Nagios can be configured to support distributed monitoring of network services and resources.

86. What Is The Difference Between Nagiosxi And Nagios Core?


NagiosXI is a Paid version and Nagios core is a free version.NagiosXI includes lot of features which we can modify using web interface. Nagios Core default not include all the features we have to implement by installing plugins.

87. How Do I Use Plugin X?


We have to download the plugins from nagios exchange Then check the nagios plugin by running manually.Most all plugins will display basic usage information when you execute them using ‘-h’ or ‘–help’ on the command line.

88. What Are Objects?


Objects are all the elements that are involved in the monitoring and notification logic.

89.Describe the Nagios Network Analyzer?


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.

90.Write down the protocols that support Nagios?


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

91.what do you understand by the fact that Nagios is object-oriented?


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.

92.Can I use Nagios for both cloud computing and cloud monitoring?


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.

93.state the name of any four virtualization platforms that supports Nagios?


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

94.What database format Nagios support to store status data?


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

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