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Monit is a lightweight Unix utility that checks local services and system objects on a recurring schedule. It can report status and, when configured, send alerts or take actions such as starting or restarting a service. It is designed for checks on the host where it runs; for centralized oversight of multiple Monit-enabled hosts, the project points to M/Monit.
What Monit monitors and what it can do
The official manual describes Monit as a utility for managing and monitoring processes, programs, files, directories and filesystems on a Unix system. Its checks can also cover network services and local system resources. See the Monit manual for the supported check types and configuration details.
- Processes and programs: Check whether a process is running or responding, and monitor resource use.
- Files and directories: Test specified conditions or detect defined changes.
- Filesystems: Check a filesystem against configured conditions.
- Network services: Test network endpoints and protocols.
- Local system resources: Monitor selected resources against configured thresholds.
A check can be configured to send an alert or perform an action, such as starting, stopping or restarting a service, unmonitoring it, or running a program. These are configured responses to conditions—not diagnoses of the underlying cause or a guarantee that a service will recover.
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How Monit works
Monit reads a run-control file—commonly named monitrc—that defines the objects to monitor, the conditions to test and any responses to take. In daemon mode, it runs checks at a configured interval, waits, and repeats. You choose the interval and rules for the workload and failure conditions you care about.
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That makes Monit useful when an operator wants supervision close to a Unix host: it can notice a defined failure and alert or act without relying on a separate monitoring service. Its checks and actions still need deliberate configuration. For example, an automatic restart may bring back a stopped service, but an unsuitable rule can produce repeated restarts or obscure a deeper fault.
Getting started safely
- Choose what to monitor. Identify the service or resource and the specific failure condition that matters. Prefer a test that reflects whether the service is actually responding, rather than only whether a process exists.
- Write a control-file entry. Define the check and any alert or action in the Monit control file. The file location and service definitions can vary with the operating system package and administrator configuration; consult the installed manual and your distribution’s package documentation.
- Validate the configuration. Run
monit -tto check the control file for syntax errors before starting the daemon. - Start Monit using the host’s service manager. Use the service-management method expected by your operating system or package. Do not assume the command or unit name is identical across Unix-like systems.
- Confirm status and alerts. Check that Monit is running and that the configured test produces the expected status or notification. Test automatic actions in the target environment before depending on them.
The manual also documents a built-in HTTP(S) interface. If you enable it, follow the current manual’s configuration guidance and expose it only where intended; do not assume its settings are secure for every installation.
Monit versus centralized multi-host management
Monit runs checks on the host where it is installed. The official site describes M/Monit as an extension for managing Monit-enabled hosts centrally. Choose based on scope: Monit fits local service supervision, while centralized oversight across multiple hosts is the role the project assigns to M/Monit. Details about M/Monit’s availability and commercial terms are not established here.
Versions and platform availability
The official download page currently labels its offering Monit 6.0.0 and lists precompiled binaries for Linux x64 and ARM variants, macOS x64, FreeBSD, OpenBSD, NetBSD, DragonFly BSD, AIX, Solaris and illumos. The page also notes that most Unix distributions include Monit. These listings and package versions can change, so check your operating system’s package manager and the project’s official download page for the version available to you before following version-specific instructions.
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