---
name: "esm"
section: "4"
platform: "openbsd"
package: "man"
version: "8.0-current-20261101"
release: "OpenBSD 8.0-current (2026-11-01)"
platforms: ["openbsd"]
url: "https://new.carta.tech/esm/4"
---

# esm(4)

Dell Embedded Server Management

## NAME

**esm** – Dell Embedded Server Management

## SYNOPSIS

**esm0 at mainbus?**

## DESCRIPTION

The **esm** driver provides support for the monitoring of the environmental sensors present in a variety of Dell servers. The hardware monitoring is accessed via the *hw.sensors* [sysctl(8)](/sysctl/8.md) variable.

Devices compatible with the **esm** driver can provide an arbitrary set of sensors which may include the following types:

| | |
| --- | --- |
| **Sensor** | **Units** |
| temperature | uK |
| fan | RPM |
| volts | uVDC |

Sensor data is updated every 10 seconds.

The Embedded Server Management framework has been replaced in more recent Dell systems with the Intelligent Platform Management Interface. Servers using the Intelligent Platform Management Interface may be monitored by the [ipmi(4)](/ipmi/4.md) driver.

## WATCHDOG

ESM provides [watchdog(4)](/watchdog/4.md) timer functionality. Once configured, if the watchdog is not reset within a certain period of time, it will timeout and the server will reset. The reset will occur regardless of the recoverability of the hang or crash.

Example of enabling a watchdog:

```
# sysctl kern.watchdog.period=10
```

In this case if the watchdog is not reset, it'll reboot the server after roughly 10 seconds.

Example of disabling the watchdog:

```
# sysctl kern.watchdog.period=0
```

## SEE ALSO

[intro(4)](/intro/4.md), [ipmi(4)](/ipmi/4.md), [watchdog(4)](/watchdog/4.md), [sensorsd(8)](/sensorsd/8.md), [sysctl(8)](/sysctl/8.md)

## HISTORY

The **esm** driver first appeared in OpenBSD 3.9.

## AUTHORS

The **esm** driver was written by Jordan Hargrave ⟨*jordan@openbsd.org*⟩ and David Gwynne ⟨*dlg@openbsd.org*⟩.