The network monitoring tool Nagios, which is now known as Nagios Core, is a leading solution for most companies that operate on Linux. Nagios is open-source software that is used to monitor IT infrastructures. It can be used both to monitor networks—including servers, routers, switches, and services—and to send an alert to an administrator when something goes wrong or when something starts working again. It detects errors that may occur in the future and repairs them before users are affected.

An updated version of Nagios, known as Nagios XI, allows you to customize and personalize the software with additional specifications. It has a complete web and graphical user interface. It also works with pre-existing installations of Nagios and provides the monitoring of an entire system, protocol, database, application, log, and bandwidth. It is freely available for up to seven hosts with no limitation on services.

Nagios provides monitoring for each and every component of an infrastructure, including network protocols, system metrics, operating systems, and services. Simple dashboards and views save time by providing a central view of an entire process and IT network at a single glance. The interface also provides automated capacity planning through graphs of the entire infrastructure. Another helpful specification is multiple user access, which allows both stakeholders and clients to access the tool easily. Advanced user management also allows every user to view only the data that is relevant to them and that they are authorized to see.

To run this application, you need a 20 GB hard drive with at least 2 GB memory and a dual-core 2.4 GHz CPU. Your operating system must be CentOS or Red hat Enterprise Linux (RHEL) versions 6 or 7 with MySQL or MariaDB, plus a PostgreSQL database.

Like most things, Nagios gives users opportunities, but it has limitations too. First and foremost, to install or configure Nagios, you need a good understanding of Linux. While most of the Nagios interface is easy to use, not all of its plugins integrate well and they are not all high-quality.