This tool has been rewritten in Rust. The previous Python version is in the v1 branch. See Migrating from v1.x for migration.

HDD Fan control is a command line tool to dynamically control fan speed according to hard drive temperature on Linux.

This has 3 benefits:

• it allows maintaining your hard drives in the ideal temperature range to have maximum longevity and avoid overheating

Because fans will slow down or stop when not needed:

• it minimizes noise generated by the fans
• it minimizes power consumption at the same time

• When is this useful?
• Features
• Prerequisites
• Installation
  • Distribution packages
  • From source
• Configuration
  • A word of caution
  • Fan configuration
• Migrating from v1.x
• Command line usage
• systemd service
• License

HDD Fan control is useful when you have one or several hard drives with one or several fans close to them, and do not want to let the motherboard control the fan speed, because it does so either statically, or using a temperature sensor unrelated to the real drive temperature (either on the CPU or on some other place on the motherboard).

The ideal use case is for a NAS with several hard drives, a low power CPU (ie. ARM or Intel Atom) with passive cooling (no fans), and a chassis with fans close to the hard drive. It that case the CPU will generate less heat than the hard drives and it makes sense to control fan speed according to the main heat source.

• Can control several fans and/or several drives with a single invocation
• Supports 6 different ways of querying temperature:
  • hddtemp invocation
  • hddtemp daemon query
  • hdparm invocation
  • smartctl invocation (SCT)
  • smartctl invocation (SMART attributes)
  • drivetemp native kernel hwmon
• Can adapt to different fan characteristics
• Can be customized to your needs:
  • to stop fans or run them at full speed at customizable temperatures
  • to never set the fans below a certain speed (useful if the fans controlled by HDD Fan control are the only ones available in the chassis)
• Can also optionally monitor CPU temperature, and control fan speed accordingly

• A Linux distribution
• A least one SATA hard drive*, that supports:
  • Temperature querying
  • Power state querying
• A motherboard which:
  • exposes to the OS a PWM to control fan speed
  • exposes to the OS a sensor to query fan speed

Most motherboards and SATA drives fit these requirements.

* There has been reports of hddfancontrol working well with SAS drives, however this has not been thoroughly tested.

Some Linux distributions have a hddfancontrol package available in their repository:

• Alpine Linux (testing): hddfancontrol
• Arch Linux (AUR): hddfancontrol
• Fedora: hddfancontrol

See GitHub releases for Debian packages built for each tagged version.

You need a Rust build environment for example from rustup.

Run in the current repository:

cargo build --release
install -Dm 755 -t /usr/local/bin target/release/hddfancontrol

or from crates.io:

sudo cargo install --root /usr/local

Also install hdparm, smartctl and optionally hddtemp. On recent Ubuntu and other Debian derivatives: sudo apt-get install hdparm smartmontools.

See systemd service to easily manage the daemon.

The default parameters will run fans at 100% speed at temperatures > 50°C, and run them a 20% speed if < 30°C, which corresponds to the usual recommended drive operating temperature. If you are sure that there are no other components in your system that generate significant heat, if you have other fans to cool down your system, or if you have a case optimized for passive cooling, you can set minimum speed to 0%, which will stop the fans if temperature is below the minimum threshold.

Be aware that a misconfiguration of this tool can lead to a failure to cool down your system properly which can damage components or reduce their lifetime.

Before using HDD Fan control unmonitored for long period of time, I recommend keeping a minimum fan speed for security, and checking that the temperature of your system stays in reasonable range as expected.

To get the start/stop values for the --pwm parameter, you can either:

• Use the pwm-test command (hddfancontrol pwm-test ...), which will run some tests and detect the values at which the fans start and stop. However you need to have previously identified the PWM file (the --pwm parameter)
• use the pwmconfig tool.

With version 2, hddfancontrol has been completely rewritten in the Rust language. The main changes coming from version 1 are:

• hddfancontrol is a compiled binary, and does not require a Python interpreter anymore.
• Command line arguments are slightly changed, and will required to be manually adjusted, either in your hddfancontrol invocations, or in the /etc/conf.d/hddfancontrol file if you use it through the systemd service. See hddfancontrol daemon -h for a reference.
• The auto drive spin down feature has been removed. If you need it, I recommend using hd-idle (beware there are several similarly named projects), which works well alongside hddfancontrol.

Run hddfancontrol -h to get full command line reference.

As an example, the command line below will instruct HDD Fan control to:

• monitor temperature of drives /dev/sda and /dev/sdb
• control fan speed using PWM 2 and 3 in /sys/class/hwmon/hwmon1/device/
• start both fans using PWM value 200
• consider the fans will stop with PWM value 75
• never run the fans below 10% of their maximum speed
• check temperature at least every minute

hddfancontrol daemon -d /dev/sda /dev/sdb -p /sys/class/hwmon/hwmon1/device/pwm2:200:75 /sys/class/hwmon/hwmon1/device/pwm3:200:75 --min-fan-speed-prct 10 -i 1min

A systemd service file is provided to control the daemon easily. If you installed hddfancontrol from a distribution package, you likely already have it installed, otherwise you can install it from the sources of this repository with:

sudo install -Dm 644 ./systemd/hddfancontrol.service /etc/systemd/system/hddfancontrol.service
sudo install -Dm 644 ./systemd/hddfancontrol.conf /etc/conf.d/hddfancontrol

Then you need to edit the HDDFANCONTROL_DAEMON_ARGS variable in /etc/conf.d/hddfancontrol to set the parameters (drives, temperature range...).

You can then start the daemon with sudo systemctl start hddfancontrol, see its status with sudo systemctl status hddfancontrol and enable automatic startup at boot time with sudo systemctl enable hddfancontrol.

GPLv3