> ## Documentation Index
> Fetch the complete documentation index at: https://docs.vms.verolabs.co/llms.txt
> Use this file to discover all available pages before exploring further.

# Probe: service_mon

> Check systemd or Windows service state

## Description

The `service_mon` probe checks the state of an OS service (systemd unit on Linux, Windows service on Windows). Supports expecting `running` or `stopped` state.

## Config fields

| Field           | Type     | Required | Default     | Description                                          |
| --------------- | -------- | -------- | ----------- | ---------------------------------------------------- |
| `type`          | `string` | Yes      | —           | Must be `"service_mon"`                              |
| `manager`       | `string` | Yes      | —           | `"systemd"` (Linux) or `"windows_service"` (Windows) |
| `serviceName`   | `string` | Yes      | —           | Service/unit name to check                           |
| `expectedState` | `string` | No       | `"running"` | Expected state: `"running"` or `"stopped"`           |

## Metrics

| Metric                          | Type    | Description                                 |
| ------------------------------- | ------- | ------------------------------------------- |
| `vms.service_mon.status`        | status  | `up` (matches) or `down`                    |
| `vms.service_mon.restart_count` | counter | Restart count (systemd .service units only) |

## Example config

```json theme={null}
{
  "type": "service_mon",
  "manager": "systemd",
  "serviceName": "nginx",
  "expectedState": "running"
}
```

## Notes

* `manager` must match the host OS. Cross-OS (e.g. `systemd` on Windows) fails at construction.
* `restart_count` is only available for systemd `.service` units.