What is Nagios Core?
Nagios Core is an open source network monitoring software coded in C language, running on platforms such as Linux and Unix. Nagios aims to solve IT infrastructure problems that may occur without affecting business processes. Users recommend Nagios Core because Nagios has different features.
The key features of Nagios Core are:
- It can show us the instant status display on the web interface. You can fix such a possible IT problem immediately.
- In case of possible IT problem, the person who registered Nagios Core notifies that there is a problem via E-mail, SMS, etc.
- Nagios Core has plugin support. So you can use your own plugin on Nagios Core
- You can monitor information sources about the host.
- It has a parent host feature, so unnecessary alarms can be av0ided.
- It can automatically interfere with the problems in applications and services.
- It has a simple interface. That means it's so easy to use.
- It can record past information.
- You can get information about the service by monitoring the service.
Nagios Core Agents
Agents in Nagios Core are some tools that make to use this program easier. That's why agents in Nagios Core is so important.
NRPE
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.
NRDP
Nagios Remote Data Processor (NDRP) is a flexible data transport mechanism and processor for Nagios. It is designed with a simple and powerful architecture that allows for it to be easily extended and customized to fit individual users' needs.
NSClient ++
This program is mainly used to monitor Windows machines. Being installed on a remote system NSClient++ listens to port TCP 12489. The Nagios plugin that is used to collect information from this addon is called check_nt. As NRPE, NSClient++ allows to monitor the so-called private services (memory usage, CPU load, disk usage, running processes, etc.) Nagios is a host and service monitor which is designed to inform your network problems.
NCPA
The Nagios Cross Platform Agent is an open source project maintained by Nagios Enterprises. NCPA installs on Windows, Linux, and Mac OS X. Created as a scale-able API that allows flexibility and simplicity in monitoring hosts. NCPA allows multiple checks such as memory usage, CPU usage, disk usage, processes, services, and network usage. Active checks are queried through the API of the "NCPA Listener" service while passive checks are sent via the "NCPA Passive" service.
Nagios Core Plugins
Nagios Core plugins are needed when we're doing check processes. You can run plugins on command lines, it'll be very easy for you to examine hosts and services by running plugins via commands.
Nagios Core Working Principle
Check Process
There are 2 types of check processes in Nagios Core, these are:
Host check
Service check
'Host check' checks whether the devices connected to the network are working or not, and monitors the network history.
Thanks to host check, it can send ping packets to the remote device.
'Service check' works on network services, resources on the system or the network, network status, etc. 'Service check' performs a port scan and transmits to Nagios Core which port is open or not and the connections opened on the port.
Active Check
Active Check is a working principle triggered by plugins. Active Check can be done on NRPE. type:
this command to connect tcp 5666 port on remote host.
Passive Check
'Passive check' is used when there is no direct access to the server. 'Passive check' comes into play here if NRPE can't be accessed.
'Passive check' runs the remote plugin itself instead of connecting to the remote system and notifies the NSCA daemon of the situation. To do that, type:
to send check status to NSCA daemon which is in Nagios on tcp 5667 port.
Soft State
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.
Hard State
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.
Nagios Core is an open source network monitoring software coded in C language, running on platforms such as Linux and Unix. Nagios aims to solve IT infrastructure problems that may occur without affecting business processes. Users recommend Nagios Core because Nagios has different features.
The key features of Nagios Core are:
- It can show us the instant status display on the web interface. You can fix such a possible IT problem immediately.
- In case of possible IT problem, the person who registered Nagios Core notifies that there is a problem via E-mail, SMS, etc.
- Nagios Core has plugin support. So you can use your own plugin on Nagios Core
- You can monitor information sources about the host.
- It has a parent host feature, so unnecessary alarms can be av0ided.
- It can automatically interfere with the problems in applications and services.
- It has a simple interface. That means it's so easy to use.
- It can record past information.
- You can get information about the service by monitoring the service.
Nagios Core Agents
Agents in Nagios Core are some tools that make to use this program easier. That's why agents in Nagios Core is so important.
NRPE
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.
NRDP
Nagios Remote Data Processor (NDRP) is a flexible data transport mechanism and processor for Nagios. It is designed with a simple and powerful architecture that allows for it to be easily extended and customized to fit individual users' needs.
NSClient ++
This program is mainly used to monitor Windows machines. Being installed on a remote system NSClient++ listens to port TCP 12489. The Nagios plugin that is used to collect information from this addon is called check_nt. As NRPE, NSClient++ allows to monitor the so-called private services (memory usage, CPU load, disk usage, running processes, etc.) Nagios is a host and service monitor which is designed to inform your network problems.
NCPA
The Nagios Cross Platform Agent is an open source project maintained by Nagios Enterprises. NCPA installs on Windows, Linux, and Mac OS X. Created as a scale-able API that allows flexibility and simplicity in monitoring hosts. NCPA allows multiple checks such as memory usage, CPU usage, disk usage, processes, services, and network usage. Active checks are queried through the API of the "NCPA Listener" service while passive checks are sent via the "NCPA Passive" service.
Nagios Core Plugins
Nagios Core plugins are needed when we're doing check processes. You can run plugins on command lines, it'll be very easy for you to examine hosts and services by running plugins via commands.
Nagios Core Working Principle
Check Process
There are 2 types of check processes in Nagios Core, these are:
Host check
Service check
'Host check' checks whether the devices connected to the network are working or not, and monitors the network history.
Thanks to host check, it can send ping packets to the remote device.
'Service check' works on network services, resources on the system or the network, network status, etc. 'Service check' performs a port scan and transmits to Nagios Core which port is open or not and the connections opened on the port.
Active Check
Active Check is a working principle triggered by plugins. Active Check can be done on NRPE. type:
Kod:
check_nrpethis command to connect tcp 5666 port on remote host.
Passive Check
'Passive check' is used when there is no direct access to the server. 'Passive check' comes into play here if NRPE can't be accessed.
'Passive check' runs the remote plugin itself instead of connecting to the remote system and notifies the NSCA daemon of the situation. To do that, type:
Kod:
send_nscato send check status to NSCA daemon which is in Nagios on tcp 5667 port.
Soft State
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.
Hard State
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.
Source: https://www.turkhackteam.org/siber-guvenlik/1934075-nagios-core-nedir.html
Translator: theblackestday
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