fand - A simple, flexible fan control daemon

Introduction

fand is a daemon that controls the fans (and other pwm-controlled devices) in your system. It's main feature is its configurability, using a concept of thermal zones.

Features

• Configurability
• Fan curve interpolation
• Supports stable hwmon paths
• Lightweight, written in C with minimum dependencies

Zones

A zone is a collection of fans and sensors. Each sensor in a zone is polled, optionally has an offset applied, and the maximum sensor value in a zone is used to control the fans in the zone. Each fan has a curve, defined as a list of temperatures and the respective PWM values to be applied. For temperatures inbetween the defined curve points, the PWM values are interpolated automatically.

This allows you to:

• have your case fans follow both CPU temperatures and GPU temperatures
• set your AIO cooler fan speeds to follow the coolant temperatures, but also ramp up when the GPU gets hot
• have your pump speed follow the CPU temperatures but stay high when the coolant is warm
• all of the above, simultaneously!

Example

A simple config with one sensor and 2 fans:

zones:
  - name: Zone #1
    sensors:
      - path: /sys/class/hwmon/hwmon7  # NZXT Kraken coolant temperature
        index: 1
        offset: 0
    fans:
      - path: /sys/class/hwmon/hwmon5  # NCT6798 fan header #1
        index: 1
        curve:
          temperatures:
            - 25
            - 30
            - 37
            - 40
          speeds:
            - 55
            - 80
            - 220
            - 255
      - path: /sys/class/hwmon/hwmon5  # NCT6798 fan header #2
        index: 2
        curve:
          temperatures:
            - 25
            - 30
            - 37
            - 40
          speeds:
            - 55
            - 80
            - 220
            - 255

Configuration

Global options

Option	Default	Description
poll_interval	1	Polling interval in seconds

Fan options

Option	Default	Description
hysteresis	0	Minimum PWM change to trigger a write (prevents flutter)

Signal handling

Signal	Effect
SIGTERM / SIGINT	Graceful shutdown, restores automatic fan control
SIGHUP	Reload configuration without restarting

Usage

fand [config_file]

If no config file is specified, fand.conf in the current directory is used.

Dependencies

• libyaml

Limitations

• Only hwmon fans and sensors are supported
• Each zone has to have at least one fan and at least one sensor
• A fan can't be used in more than one zone (well, it can, it's just that only the last setting will be applied)