Monit

Monit is a free, open-source utility for supervising Unix services and system conditions. It is best suited to administrators running self-hosted Linux or macOS machines, including container hosts, who want failures to trigger corrective actions rather than merely appear in a dashboard. Its main advantage is the breadth of local checks and automated responses in one lightweight package; root access can be necessary for process I/O metrics, and support is community-led.

Overview

Monit watches local daemon processes and can restart a process that has stopped or stop one consuming excessive resources. It also checks files, directories, and filesystems for timestamp, checksum, or size changes, making it useful for detecting configuration drift, unexpected edits, or storage-related conditions.

Network supervision covers TCP, UDP, and Unix domain sockets, with built-in protocol checks such as HTTP and SMTP. Scheduled program or script checks can trigger an action or an alert according to the program's exit value. Monit therefore fits service-maintenance jobs where a defined failure should produce a defined response, rather than passive observation alone.

It integrates with init, upstart, and systemd and can use existing run-level scripts to manage services. In a container, it can run as PID 1, combining init duties with service monitoring in one package. That is a practical option for a compact self-hosted deployment, but it is not a cross-platform service manager: the stated operating-system coverage is Linux and macOS.

Key features

Checks and automated actions

Process, filesystem, network, and script checks can each be tied to alerts or operational responses. Restarting a failed daemon helps maintain availability without manual intervention, while stopping an over-consuming process can contain resource problems. These controls are valuable for unattended hosts, but they also make careful thresholds and actions important because an automatic response can affect a live service.

Metrics, alerts, and control

Monit monitors CPU, memory, system load, and network interfaces. Customizable error messages can be sent when conditions occur, with logging to syslog or Monit's own log file. Its built-in HTTP(S) interface displays service status and allows users to start, stop, or restart processes and enable or disable monitoring. The interface is therefore useful for operational control, not just reporting.

Service integration and security

Compatibility with init, upstart, and systemd lets Monit fit established service arrangements. The maker says it is built with OpenSSL 3.5.7 statically linked and PAM support dynamically linked. Process I/O activity metrics normally require Monit to run as root, a meaningful privilege requirement for installations that need those measurements.

Pricing

There is one free plan, with no paid tier or stated seat, quota, trial, or renewal terms. It suits users comfortable operating self-hosted software and handling their own deployment. The trade-off is that support is not a commercial service: the maker directs questions to the community mailing list and says it does not have time to answer direct support requests.

Platforms

Monit is self-hosted on Linux and macOS, with multiple operating-system coverage within that Unix-focused scope. It supports service and VM monitoring and is agentless. Container deployments can use it as PID 1 for init and monitoring responsibilities. Windows is not among the stated platforms.

Who it's for

Choose Monit when you administer Unix hosts and want local checks to restart failed services, enforce resource responses, monitor files or endpoints, and run scripts on a schedule. It is particularly suitable for small or focused self-hosted environments and containers where a compact service supervisor is preferable.

Look elsewhere if you need Windows coverage, a vendor-backed support channel, or process I/O metrics without granting root privileges. Monit is also less suitable when you only need an interactive resource viewer and do not need automated service actions.

Pros and cons

Pros

• Corrective automation: failed or over-consuming processes can be restarted or stopped instead of merely reported.
• Broad local checks: files, filesystems, sockets, protocols, scripts, and core system resources are covered.
• Operational control: the HTTP(S) interface can change process state and monitoring status.
• Flexible deployment: init-system integration and PID 1 container use reduce the need for separate service machinery.
• No license cost: the AGPL software is priced at $0.

Cons

• Unix-only scope: stated platform coverage excludes Windows.
• Privilege requirement: root is normally needed for process I/O activity metrics.
• Community support: the maker does not provide direct support responses.

Alternatives

Glances is another free, open-source monitoring tool with Linux, macOS, Windows, Android, web, API, and self-hosted coverage; choose it when broader platform access matters, while optional features require extra dependencies.

PM2 is a freemium process manager with a free Runtime plan and a Plus plan at $79 a month; choose it when its real-time web interface and paid monitoring offering fit your deployment.

bottom (btm) is a free resource monitor for Linux, macOS, and Windows, suited to readers seeking a cross-platform monitor rather than Monit's service-remediation focus.

btop is a free Linux and macOS resource monitor under the Apache-2.0 license.

htop is freely available for Linux and macOS with source code and distribution binaries.

OpenProcMon is free, MIT-licensed, and 64-bit Windows-only; live capture requires Administrator privileges.

Process Lasso is a freemium Windows option, with single-PC subscriptions priced at $4.95 a month or $24.95 a year.

runit is a free service supervisor for Linux, macOS, and self-hosted deployments.

For broader category browsing, see Process Monitoring Software and Infrastructure Monitoring.

Verdict

Monit is a strong choice for administrators who want free, self-hosted Linux or macOS supervision with checks that can repair service failures, enforce resource responses, and operate inside containers. Choose it for that combination of local control and automation; look elsewhere for Windows support, direct vendor assistance, or I/O metrics that cannot depend on root access.