Nagios MCQs and Answers with Explanation: Candidates searching for top Nagios MCQ Questions and Answers to prepare for an interview or placement exam can make use of this article. However, first, check out “What is Nagios” through this section and then proceed to the Nagios Quiz to test your knowledge. Nagios is a popular open-source monitoring system that widely monitors IT infrastructure and network services. It allows users to monitor servers, applications, and services to ensure their availability and performance. Nagios is highly configurable and customizable, making it a favorite tool among system administrators and IT professionals.
Nagios MCQ Questions and Answers
To test your knowledge of Nagios, you may go through these Nagios Multiple Choice Questions that cover various aspects of the system. In this article, we will provide you with a collection of Nagios MCQs and answers to help you test and improve your understanding of this powerful monitoring tool.
Nagios Multiple Choice Questions
Name | Nagios |
Exam Type | MCQ (Multiple Choice Questions) |
Category | Technical Quiz |
Mode of Quiz | Online |
Top 61 Nagios MCQ Questions and Answers | Nagios Quiz
1. Which command is used to start the Nagios daemon?
a) nagios -d
b) nagios -f
c) nagios -s
d) nagios -r
Answer: a) nagios -d
Explanation: The command “nagios -d” is used to start the Nagios daemon in debug mode, which allows you to see detailed information about what the daemon is doing.
2. What is the default location of the Nagios configuration file?
a) /etc/nagios.cfg
b) /etc/nagios/nagios.cfg
c) /usr/local/nagios/etc/nagios.cfg
d) /usr/local/etc/nagios.cfg
Answer: c) /usr/local/nagios/etc/nagios.cfg
Explanation: The default location of the Nagios configuration file is /usr/local/nagios/etc/nagios.cfg.
3. Which command is used to check the syntax of the Nagios configuration files?
a) nagios -v
b) nagios -s
c) nagios -c
d) nagios -t
Answer: a) nagios -v
Explanation: The command “nagios -v” is used to check the syntax of the Nagios configuration files.
4. Which command is used to restart the Nagios daemon?
a) nagios -r
b) nagios -s
c) nagios -f
d) nagios -restart
Answer: b) nagios -s
Explanation: The command “nagios -s” is used to restart the Nagios daemon.
5. Which command is used to stop the Nagios daemon?
a) nagios -k
b) nagios -s
c) nagios -f
d) nagios -stop
Answer: a) nagios -k
Explanation: The command “nagios -k” is used to stop the Nagios daemon.
6. What is the purpose of the Nagios Core API?
a) To allow external applications to interact with Nagios
b) To provide an interface for creating custom plugins
c) To manage Nagios configuration files
d) To provide web-based access to Nagios
Answer: a) To allow external applications to interact with Nagios
Explanation: The purpose of the Nagios Core API is to allow external applications to interact with Nagios and retrieve information about hosts, services, and other objects.
7. What is the purpose of the Nagios Plugin API?
a) To allow external applications to interact with Nagios
b) To provide an interface for creating custom plugins
c) To manage Nagios configuration files
d) To provide web-based access to Nagios
Answer: b) To provide an interface for creating custom plugins
Explanation: The purpose of the Nagios Plugin API is to provide an interface for creating custom plugins that can be used to monitor hosts and services.
8. Which plugin is used to monitor disk space usage?
a) check_load
b) check_disk
c) check_ping
d) check_http
Answer: b) check_disk
Explanation: The check_disk plugin is used to monitor disk space usage on a host.
9. Which plugin is used to monitor CPU usage?
a) check_load
b) check_disk
c) check_ping
d) check_cpu
Answer: a) check_load
Explanation: The check_load plugin is used to monitor CPU usage on a host.
10. Which plugin is used to monitor network connectivity?
a) check_load
b) check_disk
c) check_ping
d) check_network
Answer: c) check_ping
Explanation: The check_ping plugin is used to monitor network connectivity by sending ICMP echo requests (ping) to a host and checking for a response.
11. What is a host group in Nagios?
a) A group of hosts with similar characteristics
b) A group of services with similar characteristics
c) A group of users with similar permissions
d) A group of plugins with similar functionality
Answer: a) A group of hosts with similar characteristics
Explanation: A host group in Nagios is a logical grouping of hosts that share similar characteristics, such as location, function, or operating system.
12. What is a service group in Nagios?
a) A group of hosts with similar characteristics
b) A group of services with similar characteristics
c) A group of users with similar permissions
d) A group of plugins with similar functionality
Answer: b) A group of services with similar characteristics
Explanation: A service group in Nagios is a logical grouping of services that share similar characteristics, such as function, application, or type.
13. What is the purpose of the Nagios Event Broker?
a) To allow external applications to interact with Nagios
b) To provide an interface for creating custom plugins
c) To manage Nagios configuration files
d) To allow processing of Nagios events by external applications
Answer: d) To allow processing of Nagios events by external applications
Explanation: The purpose of the Nagios Event Broker is to allow processing of Nagios events by external applications, such as event loggers or correlation engines.
14. What is the purpose of the Nagios Remote Plugin Executor (NRPE)?
a) To allow external applications to interact with Nagios
b) To provide an interface for creating custom plugins
c) To manage Nagios configuration files
d) To execute Nagios plugins on remote hosts
Answer: d) To execute Nagios plugins on remote hosts
Explanation: The purpose of the Nagios Remote Plugin Executor (NRPE) is to execute Nagios plugins on remote hosts and report the results back to the Nagios server.
15. Which configuration file is used to define host objects in Nagios?
a) hosts.cfg
b) services.cfg
c) commands.cfg
d) contacts.cfg
Answer: a) hosts.cfg
Explanation: The hosts.cfg configuration file is used to define host objects in Nagios.
16. Which configuration file is used to define service objects in Nagios?
a) hosts.cfg
b) services.cfg
c) commands.cfg
d) contacts.cfg
Answer: b) services.cfg
Explanation: The services.cfg configuration file is used to define service objects in Nagios.
17. Which configuration file is used to define check commands in Nagios?
a) hosts.cfg
b) services.cfg
c) commands.cfg
d) contacts.cfg
Answer: c) commands.cfg
Explanation: The commands.cfg configuration file is used to define check commands in Nagios.
18. Which configuration file is used to define contact objects in Nagios?
a) hosts.cfg
b) services.cfg
c) commands.cfg
d) contacts.cfg
Answer: d) contacts.cfg
Explanation: The contacts.cfg configuration file is used to define contact objects in Nagios.
19. What is a dependency in Nagios?
a) A relationship between two services
b) A relationship between two hosts
c) A relationship between a service and a host
d) A relationship between two service groups
Answer: c) A relationship between a service and a host
Explanation: A dependency in Nagios is a relationship between a service and a host, indicating that the service depends on the host is up and running.
20. What is a parent in Nagios?
a) A host that another host depends on
b) A service that another service depends on
c) A contact that receives notifications for a host or service
d) A plugin that provides functionality to Nagios
Answer: a) A host that another host depends on
Explanation: A parent in Nagios is a host that another host depends on. This allows for hierarchical dependencies between hosts, so that the status of child hosts is dependent on the status of their parent hosts.
21. What is a contact group in Nagios?
a) A group of hosts with similar characteristics
b) A group of services with similar characteristics
c) A group of users with similar permissions
d) A group of plugins with similar functionality
Answer: c) A group of users with similar permissions
Explanation: A contact group in Nagios is a logical grouping of users who are to be notified when a host or service goes down or recovers.
22. What is a notification in Nagios?
a) A message sent to a user or group of users when a host or service goes down or recovers
b) A log entry indicating that a plugin was executed
c) A report generated by Nagios showing the status of hosts and services
d) A warning message displayed in the Nagios web interface
Answer: a) A message sent to a user or group of users when a host or service goes down or recovers
Explanation: A notification in Nagios is a message sent to a user or group of users when a host or service goes down or recovers. Notifications can be sent via email, SMS, or other methods.
23. What is a check interval in Nagios?
a) The frequency at which a check is performed on a host or service
b) The amount of time a host or service must be down before a notification is sent
c) The amount of time a host or service must be up before a recovery notification is sent
d) The amount of time between two consecutive notifications
Answer: a) The frequency at which a check is performed on a host or service
Explanation: A check interval in Nagios is the frequency at which a check is performed on a host or service. The check interval is specified in seconds.
24. What is a retry interval in Nagios?
a) The frequency at which a check is retried on a host or service that has previously failed a check
b) The amount of time a host or service must be down before a notification is sent
c) The amount of time a host or service must be up before a recovery notification is sent
d) The amount of time between two consecutive notifications
Answer: a) The frequency at which a check is retried on a host or service that has previously failed a check
Explanation: A retry interval in Nagios is the frequency at which a check is retried on a host or service that has previously failed a check. The retry interval is specified in seconds.
25. What is a freshness threshold in Nagios?
a) The amount of time a check result can be considered valid
b) The amount of time a host or service must be down before a notification is sent
c) The amount of time a host or service must be up before a recovery notification is sent
d) The amount of time between two consecutive notifications
Answer: a) The amount of time a check result can be considered valid
Explanation: A freshness threshold in Nagios is the amount of time a check result can be considered valid) If a check result is older than the freshness threshold, Nagios will retry the check.
26. What is a flap detection in Nagios?
a) A mechanism to detect when a host or service is flapping between up and down states
b) A mechanism to detect when a plugin is malfunctioning
c) A mechanism to detect when a host or service has stopped responding
d) A mechanism to detect when a host or service has exceeded a specified response time
Answer: a) A mechanism to detect when a host or service is flapping between up and down states
Explanation: Flap detection in Nagios is a mechanism that detects when a host or service is flapping between up and down states. Flapping is when a host or service is constantly changing its state, going from up to down and back up again.
27. What is an event handler in Nagios?
a) A script that is executed when a host or service changes state
b) A script that is executed periodically to check the status of a host or service
c) A script that is executed to send notifications to contacts
d) A script that is executed to generate reports
Answer: a) A script that is executed when a host or service changes state
Explanation: An event handler in Nagios is a script that is executed when a host or service changes state. Event handlers can be used to perform various tasks, such as restarting a service or performing a diagnostic test.
28. What is performance data in Nagios?
a) Additional information returned by a plugin that can be used for graphing and analysis
b) The output of a plugin indicating the status of a host or service
c) The interval at which a check is performed on a host or service
d) The interval at which notifications are sent to contacts
Answer: a) Additional information returned by a plugin that can be used for graphing and analysis
Explanation: Performance data in Nagios is additional information returned by a plugin that can be used for graphing and analysis. Performance data can include metrics such as CPU usage, memory usage, and network throughput.
29. What is a passive check in Nagios?
a) A check performed by a Nagios plugin
b) A check initiated by the monitored host or service
c) A check initiated by an external system
d) A check where the results are submitted to Nagios by an external system
Answer: d) A check where the results are submitted to Nagios by an external system
Explanation: A passive check in Nagios is a check where the results are submitted to Nagios by an external system. Passive checks are useful for monitoring systems that do not have a Nagios agent installed)
30. What is a freshness check in Nagios?
a) A check performed to ensure that a check result is fresh
b) A check to ensure that a host or service has not exceeded a specified response time
c) A check to ensure that a plugin is functioning correctly
d) A check to ensure that a host or service has not stopped responding
Answer: a) A check performed to ensure that a check result is fresh
Explanation: A freshness check in Nagios is a check performed to ensure that a check result is fresh. If a check result is older than the freshness threshold, Nagios will retry the check.
31. What is the purpose of the Nagios command file?
a) To store configuration information for Nagios
b) To store check results for hosts and services
c) To store log files for Nagios
d) To accept commands from external systems to modify the state of hosts and services
Answer: d) To accept commands from external systems to modify the state of hosts and services
Explanation: The Nagios command file is used to accept commands from external systems to modify the state of hosts and services. This can be useful for automating tasks such as restarting a service or acknowledging a problem.
32. What is the purpose of the Nagios service group?
a) To group related services together for monitoring purposes
b) To group related services together for notification purposes
c) To group related services together for reporting purposes
d) To group related services together for graphing and analysis purposes
Answer: a) To group related services together for monitoring purposes
Explanation: The Nagios service group is used to group related services together for monitoring purposes. This can make it easier to manage large numbers of services, as you can assign multiple services to a single group.
33. What is the purpose of the Nagios host group?
a) To group related hosts together for monitoring purposes
b) To group related hosts together for notification purposes
c) To group related hosts together for reporting purposes
d) To group related hosts together for graphing and analysis purposes
Answer: a) To group related hosts together for monitoring purposes
Explanation: The Nagios host group is used to group related hosts together for monitoring purposes. This can make it easier to manage large numbers of hosts, as you can assign multiple hosts to a single group.
34. Which of the following is an example of a passive check in Nagios?
a) A plugin that checks the disk space usage on a host
b) A plugin that checks the CPU load on a host
c) A plugin that receives data from an external system and updates the status of a service
d) A plugin that connects to a network service and checks its availability
Answer: c) A plugin that receives data from an external system and updates the status of a service
Explanation: A passive check in Nagios is a check that is initiated by an external system, rather than by Nagios itself. An example of a passive check is a plugin that receives data from an external system and updates the status of a service.
35. Which of the following is an example of an active check in Nagios?
a) A plugin that checks the disk space usage on a host
b) A plugin that receives data from an external system and updates the status of a service
c) A plugin that connects to a network service and checks its availability
d) A plugin that monitors the log files on a host for specific events
Answer: a) A plugin that checks the disk space usage on a host
Explanation: An active check in Nagios is a check that is initiated by Nagios itself, rather than by an external system. An example of an active check is a plugin that checks the disk space usage on a host.
36. What is a service check in Nagios?
a) A check that verifies the status of a specific service on a host
b) A check that verifies the status of a specific host on the network
c) A check that verifies the status of all services on a host
d) A check that verifies the status of all hosts on the network
Answer: a) A check that verifies the status of a specific service on a host
Explanation: A service check in Nagios is a check that verifies the status of a specific service on a host. This can include checks such as verifying that a web server is responding, or that a database server is running.
37. What is a host check in Nagios?
a) A check that verifies the status of a specific service on a host
b) A check that verifies the status of a specific host on the network
c) A check that verifies the status of all services on a host
d) A check that verifies the status of all hosts on the network
Answer: b) A check that verifies the status of a specific host on the network
Explanation: A host check-in Nagios is a check that verifies the status of a specific host on the network. This can include checks such as verifying that a host is online and responding to ping requests.
38. Which of the following is a valid Nagios object type?
a) Plugin
b) Service
c) Host
d) Command
Answer: c) Host
Explanation: In Nagios, a host is a valid object type. Other valid object types include services, contacts, and time periods.
39. Which of the following is an example of a valid Nagios command?
a) check_http -H www.example.com -p 80
b) host www.example.com { check_command check_ping }
c) define host { www.example.com, 19b)168.a)10 }
d) define service { http, www.example.com, check_http }
Answer: d) define service { http, www.example.com, check_http }
Explanation: This is a valid Nagios command that defines a service object. It specifies the service name, host name, and the check command to use.
40. What is a Nagios plugin?
a) A module that adds additional functionality to Nagios
b) A script that performs a check and returns a result to Nagios
c) A graphical interface for managing Nagios configuration
d) A web application that provides monitoring data to Nagios
Answer: b) A script that performs a check and returns a result to Nagios
Explanation: A Nagios plugin is a script that performs a check and returns a result to Nagios. Plugins can be written in any programming language and can be used to perform a wide variety of checks.
41. Which of the following is a valid Nagios plugin output format?
a) CSV
b) JSON
c) HTML
d) XML
Answer: b) JSON
Explanation: Nagios plugins can output their results in a variety of formats, including JSON, XML, and plain text. This can be useful for integrating Nagios with other systems or for processing the results of checks programmatically.
42. Which of the following is a valid Nagios performance metric?
a) CPU utilization
b) Memory usage
c) Network bandwidth
d) All of the above
Answer: d) All of the above
Explanation: Nagios can collect performance data for a wide variety of metrics, including CPU utilization, memory usage, network bandwidth, and many others.
43. What is the purpose of Nagios escalation?
a) To send alerts to multiple contacts until one of them responds
b) To perform a series of checks on a service or host before sending an alert
c) To modify the behavior of Nagios based on the time of day or day of the week
d) To adjust the threshold for a service or host based on its historical performance
Answer: a) To send alerts to multiple contacts until one of them responds
Explanation: Nagios escalation is used to send alerts to multiple contacts until one of them responds. This can be useful for ensuring that critical alerts are addressed in a timely manner.
44. Which of the following is a valid Nagios escalation option?
a) Retry interval
b) Criticality level
c) Notification frequency
d) Plugin command
Answer: a) Retry interval
Explanation: A retry interval is a valid Nagios escalation option. It specifies the amount of time that should elapse between attempts to notify a contact about a problem.
45. Which of the following is a valid Nagios object attribute?
a) Color
b) Font
c) Alias
d) Size
Answer: c) Alias
Explanation: Alias is a valid Nagios object attribute. It is used to provide an alternate name for an object that is more meaningful or easier to remember than its formal name.
46. What is a Nagios check command?
a) A command that runs a plugin and returns its output to Nagios
b) A command that is executed on a remote host by Nagios
c) A command that is used to modify the configuration of Nagios
d) A command that is used to schedule checks at regular intervals
Answer: a) A command that runs a plugin and returns its output to Nagios
Explanation: A Nagios check command is a command that runs a plugin and returns its output to Nagios. Check commands can be defined in the Nagios configuration and can be used to perform a wide variety of checks.
47. Which of the following is a valid Nagios plugin return code?
a) OK
b) Warning
c) Error
d) Fatal
Answer: a) OK
Explanation: Nagios plugins can return a variety of codes, including OK, Warning, Critical, and Unknown. These codes are used to indicate the status of a service or host.
48. What is a Nagios contact group?
a) A group of Nagios users who are responsible for a set of services or hosts
b) A group of Nagios objects that share common characteristics
c) A group of Nagios plugins that are used to monitor a particular service or host
d) A group of Nagios escalation options that are applied to a service or host
Answer: a) A group of Nagios users who are responsible for a set of services or hosts
Explanation: A Nagios contact group is a group of Nagios users who are responsible for a set of services or hosts. When a service or host has a problem, Nagios will notify all members of the contact group.
49. What is a Nagios service dependency?
a) A relationship between two Nagios services that requires one service to be functioning correctly in order for the other to function correctly
b) A relationship between a Nagios service and a host that requires the host to be functioning correctly in order for the service to function correctly
c) A relationship between two Nagios hosts that requires one host to be functioning correctly in order for the other to function correctly
d) A relationship between a Nagios object and a contact group that requires the contact group to be notified if the object has a problem
Answer: a) A relationship between two Nagios services that requires one service to be functioning correctly in order for the other to function correctly
Explanation: A Nagios service dependency is a relationship between two Nagios services that requires one service to be functioning correctly in order for the other to function correctly. This can be useful for modeling complex dependencies between services.
50. What is a Nagios event handler?
a) A script that is executed when a service or host has a problem
b) A plugin that is used to perform a check on a service or host
c) A user-defined function that is used to process Nagios configuration files
d) A command that is used to schedule service or host checks at regular intervals
Answer: a) A script that is executed when a service or host has a problem
Explanation: A Nagios event handler is a script that is executed when a service or host has a problem. Event handlers can be used to perform additional actions when a problem is detected, such as restarting a service or notifying an external system.
51. Which of the following is a valid Nagios performance data format?
a) String
b) Integer
c) Float
d) Boolean
Answer: c) Float
Explanation: Nagios performance data is typically provided in a key-value format, with the value being a floating-point number that represents some measure of performance, such as response time or memory usage.
52. What is a Nagios contact?
a) A user who is responsible for a set of services or hosts
b) A Nagios object that represents a network device or service
c) A script that is executed by Nagios to check the status of a service or host
d) A group of Nagios objects that share common characteristics
Answer: a) A user who is responsible for a set of services or hosts
Explanation: A Nagios contact is a user who is responsible for a set of services or hosts. When a service or host has a problem, Nagios will notify the contacts who are responsible for that service or host.
53. What is a Nagios service?
a) A Nagios object that represents a network device or system
b) A user who is responsible for a set of services or hosts
c) A script that is executed by Nagios to check the status of a service or host
d) A group of Nagios objects that share common characteristics
Answer: c) A script that is executed by Nagios to check the status of a service or host
Explanation: A Nagios service is a script that is executed by Nagios to check the status of a service or host. Services can be defined in the Nagios configuration and can be used to monitor a wide variety of systems and applications.
54. What is a Nagios host group?
a) A group of Nagios objects that share common characteristics
b) A group of Nagios users who are responsible for a set of services or hosts
c) A group of Nagios plugins that are used to monitor a particular service or host
d) A group of Nagios escalation options that are applied to a service or host
Answer: a) A group of Nagios objects that share common characteristics
Explanation: A Nagios host group is a group of Nagios objects that share common characteristics, such as geographic location or functional role. Host groups can be used to simplify the management and monitoring of large numbers of hosts.
55. What is a Nagios service group?
a) A group of Nagios objects that share common characteristics
b) A group of Nagios users who are responsible for a set of services or hosts
c) A group of Nagios plugins that are used to monitor a particular service or host
d) A group of Nagios escalation options that are applied to a service or host
Answer: c) A group of Nagios plugins that are used to monitor a particular service or host
Explanation: A Nagios service group is a group of Nagios plugins that are used to monitor a particular service or host. Service groups can be used to simplify the management and monitoring of large numbers of services.
56. What is a Nagios check interval?
a) The amount of time that Nagios should wait between checks of a particular service or host
b) The amount of time that Nagios should wait before notifying contacts of a problem
c) The amount of time that Nagios should wait before escalating a problem to a higher-level contact
d) The amount of time that Nagios should wait before executing a recovery action for a service or host
Answer: a) The amount of time that Nagios should wait between checks of a particular service or host
Explanation: A Nagios check interval is the amount of time that Nagios should wait between checks of a particular service or host. The check interval can be specified in the Nagios configuration and can be used to control the frequency of checks for different services and hosts.
57. What is a Nagios notification interval?
a) The amount of time that Nagios should wait between checks of a particular service or host
b) The amount of time that Nagios should wait before notifying contacts of a problem
c) The amount of time that Nagios should wait before escalating a problem to a higher-level contact
d) The amount of time that Nagios should wait before executing a recovery action for a service or host
Answer: b) The amount of time that Nagios should wait before notifying contacts of a problem
Explanation: A Nagios notification interval is the amount of time that Nagios should wait before notifying contacts of a problem with a particular service or host. The notification interval can be specified in the Nagios configuration and can be used to control how often contacts are notified of problems.
58. What is a Nagios service template?
a) A set of predefined values that can be used to configure a new service object
b) A configuration file that specifies the parameters for a particular Nagios object
c) A set of instructions that define how Nagios should monitor a service or host
d) A plugin that is used to gather performance data for a service or host
Answer: a) A set of predefined values that can be used to configure a new service object
Explanation: A Nagios service template is a set of predefined values that can be used to configure a new service object. Service templates are useful for simplifying the process of configuring services with similar characteristics, as they can be used to automatically apply common values to multiple services.
59. What is the Nagios Event Broker?
a) A Nagios plugin that allows Nagios to receive events from external systems
b) A Nagios component that allows for the processing of performance data
c) A Nagios feature that allows for the execution of custom code in response to Nagios events
d) A Nagios tool that allows for the collection and analysis of log data
Answer: c) A Nagios feature that allows for the execution of custom code in response to Nagios events
Explanation: The Nagios Event Broker is a Nagios feature that allows for the execution of custom code in response to Nagios events. The Event Broker can be used to extend Nagios functionality by allowing custom code to be executed when specific events occur.
60. What is the purpose of Nagios plugins?
a) To monitor the status of services and hosts
b) To configure Nagios objects
c) To define Nagios notification options
d) To execute custom code in response to Nagios events
Answer: a) To monitor the status of services and hosts
Explanation: The purpose of Nagios plugins is to monitor the status of services and hosts. Nagios plugins are typically small scripts or executables that perform specific checks to determine the status of a particular service or host.
61. What is the purpose of Nagios macros?
a) To define Nagios notification options
b) To configure Nagios objects
c) To provide a way to reference dynamic values in Nagios configurations
d) To execute custom code in response to Nagios events
Answer: c) To provide a way to reference dynamic values in Nagios configurations
Explanation: The purpose of Nagios macros is to provide a way to reference dynamic values in Nagios configurations. Macros are used to insert values such as host and service names, contact information, and other variables into Nagios configuration files.
Nagios is an essential tool for monitoring and ensuring the availability and performance of IT infrastructure and network services. By testing your knowledge of Nagios with Top Nagios MCQ Questions and Answers, you can improve your understanding of this powerful tool and enhance your ability to manage and troubleshoot IT systems effectively. With the collection of Nagios MCQs with Answers provided in this article, you can test your knowledge and further enhance your skills in using this valuable monitoring system. Don’t forget to follow our Freshersnow portal regularly to get such useful articles.