@itworld4u Basic architecture of Nagios Server

Thank You for landing on this page, if you are looking for basic architecture of the Nagios Server than you are in right place. This is my Four steemit post, in this post I Tell You Basic architecture of Nagios Server

Nagios Server Required:-

1. HTTP (web service)
2. Nagios core package.
3. PHP Package.
4. Nagios plugins.
   (Provide different types of services set client ip).
5. Nagios server port.
6. NRPE Package (Nagios remote plugins executor).

Nagios Server Client Required :-

1. Install NRPE Package to client site.

What is Nagios?

Nagios monitors your entire infrastructure to ensure systems, applications, services, and business processes are functioning properly.

There are two types of Nagios Active checks and Passive Checks.

In Active Checks :-
Active Checks are initiated by the nagios process.
Active checks are run on regularly scheduled basis.

In Passive Checks :
Passive Checks are initiated and performed by external applications/processes
Passive Checks results are submitted to nagios for processing.

There are four objects in Nagios

Hosts
Services
Commands
Contacts

There are two state in nagios Soft and Hard state.

Soft States

Soft states occur in the following situations...

• When a service or host check results in a non-OK or non-UP state and the service check has not yet been (re)checked the number of times specified by the max_check_attempts directive in the service or host definition. This is called a soft error.
• When a service or host recovers from a soft error. This is considered a soft recovery.
The following things occur when hosts or services experience SOFT state changes:
• The SOFT state is logged.
• Event handlers are executed to handle the SOFT state.

SOFT states are only logged if you enabled the log_service_retries or log_host_retries options in your main configuration file.

The only important thing that really happens during a soft state is the execution of event handlers. Using event handlers can be particularly useful if you want to try and proactively fix a problem before it turns into a HARD state. The $HOSTSTATETYPE$ or $SERVICESTATETYPE$ macros will have a value of "SOFT" when event handlers are executed, which allows your event handler scripts to know when they should take corrective action. More information on event handlers can be found here.

Hard States

Hard states occur for hosts and services in the following situations:
• When a host or service check results in a non-UP or non-OK state and it has been (re)checked the number of times specified by the max_check_attempts option in the host or service definition. This is a hard error state.
• When a host or service transitions from one hard error state to another error state (e.g. WARNING to CRITICAL).
• When a service check results in a non-OK state and its corresponding host is either DOWN or UNREACHABLE.
• When a host or service recovers from a hard error state. This is considered to be a hard recovery.
• When a passive host check is received. Passive host checks are treated as HARD unless the
passive_host_checks_are_soft option is enabled.

The following things occur when hosts or services experience HARD state changes:

• The HARD state is logged.
• Event handlers are executed to handle the HARD state.
• Contacts are notifified of the host or service problem or recovery.

Nagios NRPE Port number is 5666.