Nagios Monitoring System

1, Nagios is an open-source free network monitoring tool, you can monitor Windows, Linux and UNIX host status, switch routers and other network equipment, in the system or service status anomalies when sending mail or SMS alarm, the first time to notify the site operations personnel. Traffic monitoring is not his forte, traffic monitoring recommends using cacti (can draw very intuitive graphics. 2. Nagios Working principle
Nagios itself does not include the ability to monitor hosts and services. All monitoring and monitoring functions are done through a variety of plugins. After installing Nagios, the/libexex in the Nagios home directory is included with Nagios's plugin, such as: Check_disk is the plug-in that checks the disk space, Check_load is the plug-in that checks the CPU load, each plug-in can run. check_xxx-h command to check its usage and functionality.

3. Four monitoring states of Nagios

Nagios can identify four status return information. 0 (OK) indicates a healthy state (green display), 1 (WARNING) indicates a warning (XXX), 2 (CRITICAL) indicates a very serious error (red), 3 (UNKNOWN) indicates an unknown error (deep xxx), Nagios determines the state of the monitored object based on the value returned by the plug-in, and is displayed through the Web for administrators to detect faults immediately.
4. Nagios manages the service work process remotely via the Nrpe plugin

1) Nagios executes the Check_nrpe plugin installed inside it and tells Check_nrpe to detect which services.

2) connect the Nrpe daemon on the remote machine via the Ssl,check_nrpe.

3) Nrpe run local plug-ins to detect the local server and status (Check_disk,... etc).

4) Nrpe The results of the test to the host side of the Check_nrpe,check_nrpe and then send the results to the Nagios state queue.

5) Nagios reads the information in the queue, then displays the results.

5. Nagios configuration file:

Nagios.cfg: Master profile, defining the name and location of various configuration files

CGI.CFG: Controlling the CGI configuration file

Resource.cfg: Resource file, define various variables so that other files can be called

Objects: Other configuration file directory, this directory is mainly:

         Command.cfg：命令配置文件，定义各种命令格式，以备其他文件调用         contacts.cfg：联系人和组，发邮件等告警信息时可以调用         localhost.cfg：监控本机的配置文件         timeperiods.cfg：定义监控时间的配置文件，便于其他文件调用         Hostgroups.cfg：定义监控的主机（组），需手动创建。

Nagios Monitoring System