What it does
Monit is a lightweight Unix system monitoring utility. Administrators define checks for services and system resources, then configure alerting or actions when a condition is met. The official manual documents checks for processes, filesystems, files, directories, hosts, and network services. Monit is free software under the GNU Affero General Public License; its related M/Monit product is a separate central manager for multiple Monit hosts.
Monit is suited to a host where a small, configuration-driven monitor is preferable to a separate hosted observability platform. An operator installs the daemon, writes checks for a process or service, sets the conditions that count as unhealthy, and chooses whether Monit should alert, restart, or otherwise act. For example, a host can be configured to watch a web service and notify an administrator if its process exits or its response stops meeting the configured check.
The important design choice is that Monit can both observe and take action. A restart rule may restore a simple service automatically, but it can also conceal a repeated failure or interrupt work if the rule is too broad. Start with notification-only checks, review event history, and enable recovery actions only when the failure condition and restart behavior are understood.
Monit is a single-host utility. The vendor describes M/Monit as a separate product for managing and monitoring multiple Monit-enabled hosts through a web interface; that is not included here. The official site states that Monit is AGPL-licensed and free to use.
Strengths
- Can monitor processes, filesystems, files, directories, hosts, and network services from a Unix host.
- Allows operators to define alerts and recovery actions in configuration.
- Free software published under the AGPL.
Watch out for
- A centralized fleet view requires the separate M/Monit product or another monitoring system.
- Automatic recovery rules need careful scoping so they do not hide recurring faults or restart a service unexpectedly.
Best for
- Unix administrators adding lightweight process and host checks to a server
- Automatically restarting a narrowly defined service after a confirmed failure condition
Sources
- Monit - utility for monitoring services on a Unix system (Oct 26, 2026)
- Monit Documentation (Oct 26, 2026)