Keeping track of your system and network is most important.
Open-source monitoring tools for Linux are:
Almost all types of components are monitored by Nagios, including network protocols, operating systems, web servers, and websites.
By consuming fewer server resources, it provides high performance.
Third-party applications can be integrated with a plugin.
Using Zabbix, you can monitor the performance and availability of servers, web applications, and databases. It is an enterprise-level software.
It uses a server-agent architecture, where you install an agent on a server (client) to be monitored by the Zabbix server. FTP, SSH, HTTP, and DNS do not require agents.
SNMP is a networking protocol used to manage and monitor network-connected devices. It provides better reporting through SNMP.
It is an open-source network monitoring tool that can be installed on Linux or Windows. Connected to RRDTool, it generates graphs of relevant network data.
In the form of charts, it presents the network statistics.
A PHP-compatible database, such as MySQL, Apache, or IIS, is required.
It facilitates administrators to create different levels of users and give them different levels of permissions based on their authority.
Icinga-2 is a free and open-source monitoring tool that provides monitoring and alerting capabilities for servers, network devices, and applications. It supports plugins for monitoring various aspects of the server and can be configured to send alerts via email.
Netdata provides real-time monitoring and performance & troubleshoot system and applications.
Using thousands of metrics, interactive visualizations, and insightful health alarms, Netdata is fast and efficient. It runs on all systems without causing disruption.
It is a free and open-source monitoring and alerting software developed on SoundCloud.
Its architecture consists of several modules called exporters that utilize metrics and key-value pairs to identify data.
The system consists of independent single server nodes.
Prometheus consists of several components, including the server, a push gateway, client libraries, and an alert manager.
Monitorix is an open-source system monitoring tool designed for Linux or UNIX systems. It is a lightweight tool for tracking and monitoring multiple devices.
It is also suitable for embedded systems due to its size and simplicity. Monitorix wrote in Perl.
Monitorix collects system and network data regularly and displays graphs on its web interface. It also monitors disk drive temperatures and health.
There are various other open-source tools available but above mentioned are some of the best open-source tools available for monitoring your server.