10 Best Open-Source Server Monitoring Tools

Server monitoring is one of the key considerations when planning out your IT infrastructure. It provides observability into the server's resources and the performance of the underlying applications. This ensures the stability, security, and health of not just the servers, but also the installed applications.

There are different types of server monitoring, each focusing on various aspects. Key categories include resource monitoring, which tracks server metrics including disk space, CPU, and memory usage. There is application monitoring, which tracks the performance and health of applications, and security monitoring that involves vulnerability detection and mitigation of threats.

Let’s now explore some of the best open-source server monitoring tools.

#Top Open-Source Server Monitoring Tools

When choosing a server monitoring solution, it's crucial to align it with your infrastructure needs. Our selection of top open-source monitoring tools is based on key factors like ease of use, technical capabilities, scalability, and community support.

#Zabbix

Zabbix is a comprehensive monitoring solution, popular for its flexibility in monitoring diverse resources in different environments. You can use it to monitor resources on your small business or home lab and even complex IT infrastructure in enterprise platforms.

Zabbix monitors a wide range of resources on your IT infrastructure: servers, VMs, network devices, applications, and IoT devices. Owing to its scalability and flexibility, it's an excellent tool for monitoring cloud and complex deployments. You can monitor pods and microservices in a Kubernetes cluster. You can also incorporate it with cloud monitoring tools like AWS CloudWatch for fine-grained monitoring.

Zabbix comprises multiple components. At its core is the Zabbix server core, which offers a PHP-driven web UI with customizable dashboards that provide a visual display of server and application metrics. This is typically installed on Linux systems.

Zabbix agents are lightweight programs installed on remote nodes to be monitored. They are cross-platform and can be installed on Windows and UNIX/Linux systems. In the backend, an SQL database stores user data and metrics. Popular choices for the database include MySQL, MariaDB, and PostgreSQL.

#Supported platforms

• Linux flavors such as Amazon Linux, Ubuntu, Debian, and RHEL-based systems (Rocky Linux, AlmaLinux, and Fedora)

• macOS, and UNIX systems, including Solaris, OpenBSD, and FreeBSD

• Windows is supported for the Zabbix agent only.

#Pros

• It's free. No licensing fee is required

• Suitable for small to large and complex environments

• All-in-one monitoring tool. Supports monitoring of servers, Virtual machines, network devices, and cloud services.

• Highly customizable through widgets, custom themes, and scripts for alerts

• Automatic discovery of network hosts

• Powerful and flexible alerting system with support for email and SMS, and integrations for channels like Slack

• REST APIs for automation

#Cons

• Complex initial setup and a steep learning curve for beginners

• The web UI has a basic appearance and is not as modern as other monitoring tools like Grafana

• High resource overhead when monitoring large environments.

#Nagios Core

Nagios offers two monitoring products: Nagios Core, an open-source monitoring solution, and Nagios XI, a commercial offering built upon Nagios Core. The latter provides advanced features, including scheduled reports, advanced monitoring, and automated configuration using REST APIs.

Trusted by millions of users globally, Nagios Core has earned its position as a reliable and effective monitoring solution for various IT resources, including servers, network services, performance, and uptime of business applications. Its plugin architecture extends its monitoring capabilities, allowing it to monitor cloud resources in AWS, GCP, and Azure.

Nagios Core tracks host status and metrics like memory, CPU load, and storage. It excels in monitoring services, including SSH, DNS, HTTP, HTTPS, and PING. Its alerting system notifies you when issues occur via email or custom channels such as SMS and scripts.

On the flipside, its basic interface and lack of advanced features make it only suitable for small and less complex IT environments.

#Supported platforms

Nagios Core is designed primarily for Linux systems (RPM-based and DEB-based distributions) and SUSE Linux. Nagios XI extends to other systems, including Windows and macOS.

#Pros

• It's lightweight and stable

• Low resource overhead

• Highly customizable with plenty of community and custom plugins

• Diverse monitoring coverage. Can monitor servers, network devices, services, protocols, etc.

• Vibrant online community with multiple forums and guides

• Powerful alerting system

#Cons

• The web UI feels dated and not as intuitive as Grafana and other tools

• Initial setup is time-consuming and daunting for beginners

• Difficulty in creating charts and dashboards compared to other tools

• Steep learning curve

• Struggles with monitoring large networks

• Lacks the auto-discovery feature. Relies on add-ons to discover hosts

#Cacti

Cacti is an excellent tool for collecting and graphing time-series data, particularly from servers and network devices such as routers, firewalls, access points, and switches.

Cacti tracks resource usage and other statistics via the SNMP protocol. An SNMP agent is installed and configured on servers (e.g., Linux and Windows systems ) and enabled on network devices to ship device data. Cacti server leverages the auto-discovery feature to pull data and start visualizing device data on graphs.

The web UI is PHP-driven, and time-series data is stored in a relational database(such as MySQL) and RRDtool. It uses built-in templates to graph metrics in user-friendly charts. You can visualize bandwidth statistics, uptime, and latency for devices.

A notable drawback of Cacti is its lack of a native alerting system. To address this limitation, you need to enable the Thold and Spine plugins to handle threshold and monitoring notifications and send alerts via email.

#Supported platforms

• Linux and UNIX

• Windows

#Pros

• Completely free. No license costs

• Excels at bandwidth monitoring with the SNMP protocol

• Excellent for monitoring network devices like switches, routers, and firewalls.

• SNMP device support

• Template-based configuration for simplified monitoring

• Scalable with Spine Poller. This is ideal for installations with several hosts and devices

• Extendable with plugins for enhanced features, e.g., alerting and notification via e-mail

#Cons

• Mostly a graphing tool for monitoring traffic and server metrics, not an alerting solution

• UI feels outdated and basic

• Initial setup of templates and SNMP configuration is time-consuming

• Not ideal for devices that do not support SNMP

• Limited application monitoring capability. Primarily an SNMP-based monitoring tool

• Limited alerting capabilities. Requires plugin support for sending alerts

#Icinga 2

A rewrite of Nagios, Icinga 2 is a modern open-source monitoring tool with an extensible UI and packed with features and plugins for monitoring network devices and servers. It's an impressive upgrade of Icinga designed to track resource performance and uptime.

It monitors a wide range of resources, including Linux and Windows servers, services such as SMTP and DNS, resource usage, and web/API endpoints. You can monitor Cloud resources on platforms such as Azure and AWS through a rich set of plugins. You can also keep an eye on Docker containers and Kubernetes resources. It provides add-ons for integration with other graphing platforms such as Graphite and InfluxDB.

Icinga 2 offers Icinga Web 2 - a modern, fast, and responsive data visualization web UI for monitoring metrics and alerts on dashboards. To monitor resources, agents are installed on monitored nodes to ship metrics to the Icinga server. Monitored data and logs are stored in a MySQL/MariaDB database.

Due to its tedious manual configuration, its steep learning curve is a deterrent for beginners.

#Supported platforms

• Linux, including Red Hat, Debian, Ubuntu, SUSE, Amazon Linux, and more

• Windows Desktop 8 and later versions

• Windows Server 2012 and later

#Pros

• Modern UI with user-friendly and intuitive dashboards

• No licensing costs.

• Highly customizable

• Plugin integration and powerful REST APIs for integration with third-party apps

• Highly scalable to monitor hundreds of hosts

• Supports complex and large environments

• Can scale to monitor thousands of hosts and services using a distributed setup.

• Strong online community with thorough product documentation

#Cons

• Steep Learning Curve

• Configuration syntax and setup can be complex, especially for beginners.

• Lacks native cloud integration for monitoring cloud-native resources e.g., microservices

• Limited capabilities for built-in alerting

• Resource overhead as more plugins are enabled

#Grafana

Grafana is an open-source visualization tool primarily meant to visualize metrics from external data sources. Once a data source is connected to Grafana, raw data is transformed into informative, appealing, and interactive dashboards and graphs.

There’s a vast array of data sources that can be integrated with Grafana. It integrates with familiar data sources such as Prometheus, Elasticsearch, and previously covered monitoring tools like Zabbix and Icinga. Other platforms include time-series databases such as Graphite and InfluxDB, SQL-based databases such as MySQL and PostgreSQL, and Cloud monitoring platforms, including Azure Monitor and AWS CloudWatch. Other data sources include enterprise solutions such as Oracle, SAP HANA, AppDynamics, Snowflake, and Wavefront, to mention a few.

Grafana offers a robust alerting system. You can easily define, manage alert rules, and dictate how to receive alert notifications. It supports integrations such as Webhooks, Slack, and Email for receiving alerts.

#Supported platforms

• Linux, including Debian, Ubuntu, Red Hat-based systems like Fedora, SUSE, and openSUSE.

• Windows Desktop 10 and later. Windows Server 2016 and later

• macOS (Apple Silicon (ARM64) and Intel architectures)

• Kubernetes using Helm charts

• Docker. Grafana offers a Docker image

#Pros

• Beautiful and sleek dashboards

• Highly customizable charts, graphs, heatmaps, tables, etc.

• Free and open-source with an option to upgrade to the Enterprise Edition for advanced monitoring features

• Extensible plugin architecture that supports multiple plugins and data sources, e.g, Loki, Elasticsearch, and Prometheus

• Powerful and flexible alerting system

• Robust and extensible API for automation and integration with other tools

• Supports multiple notification channels, including Slack Webhook, email, and PagerDuty

• Cloud-native friendly, through integration with multiple cloud resources.

#Cons

• Complex query-building, especially with data sources such as Elasticsearch

• Does not collect and store data; It only visualizes it.

• Setting up data sources is manual and can sometimes be complex

#Prometheus

Prometheus is a monitoring solution for graphing time-series data from diverse sources such as servers, applications, databases, etc. The data is stored locally on a time-series database for visualization and analysis. The insights derived from the analysis help operations teams gain deep insights into the performance and health of services and nodes.

Prometheus leverages a pull-based scraping mechanism that pulls metrics from monitored nodes instead of other monitoring tools that await data from remote nodes.

Like most monitoring systems, it offers a service auto-discovery feature that automatically discovers hosts to be monitored. Once collected, time-series data is filtered, sliced, and manipulated using PromQL - a powerful query language for visualizations and ad-hoc queries.

To monitor nodes, a Node Exporter is installed on target systems (Linux and Unix) to allow Prometheus to scrape and make sense of the data. Node exporters enable comprehensive monitoring by collecting server metrics, including CPU, disk, and memory usage, and bandwidth statistics.

You can configure alert rules sent to an AlertManager, which sorts and aggregates them before sending notifications via email and chat applications.

#Supported platforms

• Linux

• Windows

• macOS

#Pros

• PromQL for querying and analyzing time-series data

• It's a good fit for cloud-native applications. It's Kubernetes-friendly and is widely used for microservices monitoring.

• Stores metrics data locally on a time-series database. This is ideal for performance monitoring

• Automatic service discovery of network hosts and cloud services

• Provides an alert manager to handle alerts

• Integration with tools like email, Slack, and PagerDuty for sending alerts

• Large and vibrant community, boasting a thriving ecosystem of developers and users

#Cons

• The web UI is basic. Integration with Grafana is recommended for visually rich dashboards

• Has a steep learning curve due to the complexity of using PromQL and managing large datasets

• Risk of data loss due to a crash since data is stored locally. Configuration with persistent volumes is required

• Prometheus is a single-node system by design, which adds complexity when scaling horizontally.

#Netdata

Written in C, Netdata is a lightweight, yet powerful, all-in-one monitoring solution that tracks and visualizes metrics in real-time.

Netdata agents are installed on remote systems, e.g., Windows and Linux servers for server monitoring. The agents are lightweight and optimized applications that gather and ship resource and application metrics to the standalone Netdata server. Network devices are monitored using the SNMP protocol, which typically requires enabling and activating it by a network/systems administrator. Through add-ons, Netdata integrates with container runtime engines such as Docker and platforms such as Kubernetes. This allows you to monitor resources such as containers, pods, and services.

What makes Netdata stand out from the tools we have covered so far is its sub-second real-time monitoring system, which displays metrics second by second. Most tools have a monitoring interval of between 10 and 60 seconds, making it a more refined real-time monitoring solution.

Additionally, it provides stunningly beautiful and fully interactive web dashboards that offer an enhanced user experience with zoomable capabilities. Even better, the dashboards are auto-generated, and no setup is required. There’s also no need for integration with Grafana since the charts are visually rich enough, complete with auto-scaling and zoom features.

Netdata also offers anomaly detection through alerts, which can be sent from the Netdata cloud or agents. Alerts can be sent through email and channels such as Slack and Webhooks.

#Supported platforms

• Linux

• Windows

• FreeBSD and macOS

#Pros

• Real-time monitoring with per-second granularity, perfect for identifying issues as they happen

• Beautiful, Interactive Dashboards

• Built-in health checks and alerting engine

• Seamless and fast installation without much installation

• Automatically discovers services, applications, and system resources upon installation

• Built-in health checks and alerting engine

• Cloud support. Agents can be installed on cloud servers to stream metrics to a central node for monitoring

#Cons

• It's ideal for real-time monitoring, but falls short in historical or trend data analysis

• High resource usage due to real-time monitoring

• Alterting is basic and not robust

• Limited Query Language

• Custom setups for large-scale distributed environments.

#CheckMK RAW Edition

Checkmk provides four monitoring solutions: Checkmk Cloud, Checkmk Enterprise Standard, Checkmk MSP, and Checkmk RAW. The first three are commercial versions that require a paid license and are mostly tailored for enterprise and cloud-native environments.

Checkmk RAW is free under the GNU GPLv2 license and is built on Nagios core. For easier management, it has a polished and intuitive web UI for monitoring server metrics and configuring various settings.

Like Cacti, it uses RRDtool to graph and visualize metrics. The auto-discovery feature automatically detects hosts and their services on a network.

Checkmk RAW offers a rich ecosystem of plugins for monitoring every resource, including hardware, databases, OS, etc. A built-in notification system relays alerts through email or via integrations with platforms such as Telegram.

Although it lacks advanced features for enterprise environments, Checkmk RAW is ideal for small companies, home labs, and organizations looking to test-run it before upgrading to commercial editions. If you need enhanced monitoring capabilities, you can easily upgrade to commercial versions in just a few minutes.

#Supported platforms

• Linux (Debian and Ubuntu LTS versions, and Red Hat-based distros and SLES)

• Windows Server (2016, 2019, 2022, 2025)

• macOS and BSD systems

#Pros

• Free to install and use. No licensing costs

• Offers a neat and user-friendly web interface for monitoring and configuration

• Offers a Rule-based configuration ideal for handling large environments efficiently

• Supports both agent and agentless monitoring

• Supports a wide range of resources, including network devices, servers, and applications

• Automatically discovers applications and metrics

• Active online community with forums and documentation

#Cons

• Lacks Enterprise features, which are a preserve for the Enterprise edition

• The web UI is less intuitive for beginners

• The underlying complexity in configuration and setup makes for a steep learning curve for learners

• Since it's built on Nagios Core, some features are not directly upgradeable to the Enterprise edition

#ntopng

ntopng is built on top of the original ntop monitoring tool. Developed in Lua, it's a revamped version of ntop built with low-resource usage, enhanced performance, and usability in mind. So definitely, you’ll expect a lot in store in terms of enhanced user experience and more functionality.

The suffix "ng" stands for "next generation," emphasizing its re-engineered and improved model. It runs on diverse environments, including Linux and UNIX systems (FreeBSD, pfSense, and macOS) and Windows. Installation packages are available for Debian ARM and Raspberry Pi systems.

Ntopng provides a user-friendly web-based interface for tracking real-time bandwidth statistics, including historical traffic analysis. From the web UI, you can view the hosts on your network with their IP addresses, traffic breakdown (sent and received packets), and protocols in use. Additionally, it provides bandwidth consumption per application, so you can easily track bandwidth-intensive applications, such as file-sharing applications.

Ntopng works similarly to Wireshark. It uses the libpcap feature for packet sniffing on hosts' interfaces. It offers real-time visibility into traffic flows and geolocation of flows, applications, and protocols. It leverages the Deep Packet Inspection (DPI) technique via the nDPI toolkit to classify protocols. Its installation provides a Redis database to store host metadata and Flow.

You can configure alerts and thresholds to be notified when a host exceeds the bandwidth limit. A Pro license is needed for active monitoring and vulnerability scanning.

#Supported platforms

• Linux

• Windows

• macOS and FreeBSD

• pfSense/OPNsense

#Pros

• It's cross-platform and easy to install.

• Offers a modern and intuitive UI

• Supports Linux, Windows, and macOS

• It's lightweight and supports hardware with minimal resources

• Offers customizable alerts based on thresholds, anomalies and traffic patters.

• Can collect and analyze NetFlow, IPFIX and sFlow data.

• Offers security insights on threats such as suspicious traffic flows and port scanning

#Cons

• Limited features in the Free edition. Most of the advanced features e.g., advanced alerting and SNMP monitoring, are only found in Commercial editions.

• Advanced features can be intimidating to learn, especially for beginners

• Scalability challenges in large deployments. You need to upgrade to the Enterprise edition

#LibreNMS

LibreNMS is yet another open-source network monitoring system, ideally designed for monitoring the performance and metrics of network devices using the SNMP protocol. Additionally, it offers excellent server monitoring capabilities. It collects and visualizes resource usage statistics such as CPU and memory utilization in Linux and Windows hosts.

LibreNMS, like most monitoring tools we have explored, auto-discovers network hosts using protocols such as ARP and SNMP. It supports a wide range of networking vendors, including Juniper, Cisco, and Meraki.

The web UI is simple and neat with a modern touch. However, it is considered quite basic when compared with Grafana and Netdata. RRDtool is the default tool for graphing metrics. You can send metrics to Prometheus, from where metrics can be visualized in Grafana with powerful dashboards and charts.

Custom alerts can be configured and notifications relayed on various channels, including Discord, email, and Telegram.

#Supported platforms

• Linux (Both RPM-based and Red Hat-based systems)

• Docker. A Docker image is available from Docker Hub

#Pros

• Free and open-source. Hence, no licensing costs

• Great multi-vendor support. Works well with Cisco, Fortinet, HP, Mikrotik, etc

• Neat, responsive, and user-friendly web UI complete with dashboards and graphs

• Extensive graphing thanks to RRDtool-based charts and graphs, which display metrics

• Customizable alerting system that offers integration with email, Telegram, Slack, etc.

• Auto-discovery of devices. Saves time and effort in manual configuration

• Scalable enough to handle small and large networks

• Robust REST APIs for integration with external automation tools

• Vibrant community with active forums

#Cons

• Initial setup and configuration, especially for large environments, can be daunting and time-consuming

• Limited flexibility in custom visualizations since it uses RRDtool out of the box

• Resource-intensive, especially when monitoring many devices

• It's primarily an SNMP-based device monitoring, hence, limited visibility into application monitoring

• No support for modern monitoring methods such as Netflow and telemetry

#Conclusion

We have covered 10 of the most reliable open-source monitoring tools that you can leverage to monitor resources in your infrastructure. While free, some offer basic features only to monitor small networks with few resources. This will require you to upgrade to a paid version to access advanced features for enhanced monitoring capabilities.

Hopefully, you are now in a better position to choose a monitoring solution tailored to your needs. You can get started with any of these monitoring solutions by deploying a virtual server at Cherry servers to monitor your infrastructure and gather valuable insights on the health and performance of your devices and applications.