---
title: Making my UDM-Pro scream
description: Remote fan control for the Unifi Dream Machine Pro
date: 2022-04-06
tags:
- random
- hardware
draft: false
extra:
  excerpt: A project review post covering my work on remote-control for the UDM-Pro
    cooling system
aliases:
- /blog/udm-fan
---

[Ubiquiti](https://www.ui.com/)'s [Unifi Dream Machine Pro](https://www.ubnt.com/products/unifi-dream-machine-pro) is a powerful medium-scale business-oriented rack-mount router, capable of handling 10/100/1000/10000 ethernet traffic. Really quite a nice device.

One day, I had the thought: *I've never heard the fans ramp up on this*. And so, I started looking into the possibilities of manual fan control.

As it turns out, this Linux-based device allows you (like any embedded Linux computer) override its I/O with some clever shell commands.

## Enter: SSH

If you own a UDM-Pro, you surely know how to log in to it via SSH. If not, look it up :smile:.

With an SSH connection open, the following commands let you control the fans on the device!

```sh
# Override the fans with a speed (0-255)
export FAN_SPEED=128
killall -9 S04ubnt-fan-speed ubnt-fan-speed
echo 1 > /sys/class/hwmon/hwmon0/device/pwm1_enable
echo 1 > /sys/class/hwmon/hwmon0/device/pwm2_enable
echo $FAN_SPEED > /sys/class/hwmon/hwmon0/device/pwm1
echo $FAN_SPEED > /sys/class/hwmon/hwmon0/device/pwm2

# Return control back to the device
/etc/init.d/S04ubnt-fan-speed start
```

## Exit stage left

Who needs SSH anyways? 

When I discovered this, I decided to write a little program that wraps the SSH commands with a little bit of error checking, and support for auto-discovery of UDM-Pro devices on your network.

{{ github(repo="ewpratten/udm-fan") }}

<br>

The following commands can be used to control the fans on a local UDM-Pro:

```sh
# Set the fans to half speed
udm-fan set 128

# Set the fans to full speed (with a custom IP address)
udm-fan set 255 --override-ip 172.16.11.5

# Bring the fans back to automatic control
udm-fan auto
```

Passwords can be provided through:

- The `--ssh-password` flag
- The `UDM_SSH_PASS` environment variable
- A `.netrc` entry with the hostname being the UDM's IP address
- The terminal at runtime