Nagios an open-source computer-software application, monitors systems, networks and infrastructure. Nagios offers monitoring and alerting services for servers, switches, applications and services. It alerts users when things go wrong and alerts them a second time when the problem has been resolved.
Ethan Galstad and a group of developers originally wrote Nagios as NetSaint. As of 2015 they actively maintain both the official and unofficial plugins. Nagios is a recursive acronym: "Nagios Ain't Gonna Insist On Sainthood" - "sainthood" makes reference to the original name NetSaint, which changed in response to a legal challenge by owners of a similar trademark.
- Monitoring of network services (SMTP, POP3, HTTP, NNTP, ICMP, SNMP, FTP, SSH)
- Monitoring of host resources (processor load, disk usage, system logs) on a majority of network operating systems, including Microsoft Windows with the NSClient++ plugin or Check MK.
- Monitoring of anything else like probes (temperature, alarms,etc.) which have the ability to send collected data via a network to specifically written plugins
- Monitoring via remotely run scripts via Nagios Remote Plugin Executor
- Remote monitoring supported through SSH or SSL encrypted tunnels.
- A simple plugin design that allows users to easily develop their own service checks depending on needs, by using their tools of choice (shell scripts, C++, Perl, Ruby, Python, PHP, C#, etc.)
- Available data graphing plugins
- Parallelized service checks
- The ability to define network host using 'parent' hosts, allowing the detection of and distinction between hosts that are down or unreachable
- Contact notifications when service or host problems occur and get resolved (via e-mail, pager, SMS, or any user-defined method through plugin system)
- The ability to define event handlers to be run during service or host events for proactive problem resolution
- Automatic log file rotation
- Support for implementing redundant monitoring hosts
- An optional web-interface for viewing current network status, notifications, problem history, log files, etc.
- Data storage via text files rather than database
Nagios Agents
NRPE
Nagios Remote Plugin Executor (NRPE) is a Nagios agent that allows remote system monitoring using scripts that are hosted on the remote systems. It allows for monitoring of resources such as disk usage, system load or the number of users currently logged in. Nagios periodically polls the agent on remote system using the check_nrpe plugin.
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 (NRDP) is a Nagios agent with a flexible data transport mechanism and processor. It is designed with an architecture that allows it to be easily extended and customized. NRDP uses standard ports and protocols (HTTP(S) and XML) and can be implemented as a replacement for NSCA.
NSClient++
This program is mainly used to monitor Windows machines. Being installed on a remote system NSClient++ listens to port TCP 12489. 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.
Configure Nagios
Visit the below link to configure your Nagios Server
Visit the below link to configure your Nagios Client
Visit the below link to troubleshoot your Nagios Server / Client