truefan 0.9.1

Fan control daemon for TrueNAS

truefan

Fan control daemon for TrueNAS SCALE systems on Supermicro X11 boards. Reads temperatures from IPMI, SMART, NVMe, and lm-sensors, then adjusts fan duty cycles via IPMI raw commands to keep things cool with minimal noise.

Features

• Auto-detection of sensors and fans — classifies by type (cpu, drive, nvme, ambient, other) and applies per-class interpolation curves.
• Self-calibrating — learns each fan's setpoint table by ramping duty down and recording RPMs. Can be recalibrated as fans age or collect dust.
• Failsafe — fans go to 100% on crash, total sensor class failure, or stalled fan. The watchdog parent restarts the daemon automatically.
• Netdata metrics — per-sensor thermal load, per-zone duty, per-fan target RPM, and daemon restart count via statsd.

Requirements

• Python 3.11+
• ipmitool
• smartctl (smartmontools) — for SATA/SAS drive temps
• nvme-cli — for NVMe temps
• lm-sensors — for kernel-exposed sensors
• Supermicro X11 motherboard with IPMI

Install

TrueNAS SCALE doesn't ship ensurepip, so create the venv without it and bootstrap pip manually:

python3 -m venv --without-pip /mnt/pool1/venvs/truefan
source /mnt/pool1/venvs/truefan/bin/activate
curl -sS https://bootstrap.pypa.io/get-pip.py | python3
pip install truefan

Put the venv on a pool — the boot drive is wiped on OS updates.

Quick start

# Detect sensors, calibrate fans, write config
sudo truefan init

# Start the daemon
sudo truefan run

# Show detected sensors and current readings
truefan sensors

# Re-calibrate after cleaning or replacing fans
sudo truefan recalibrate

# Reload config without restarting
sudo truefan reload

Configuration

truefan init generates a truefan.toml with sensible defaults. Example:

poll_interval_seconds = 15
spindown_window_seconds = 180

[curves.drive]
temp_low = 30
temp_high = 45
duty_low = 25
duty_high = 100
fan_zones = ["peripheral"]

# Per-sensor overrides for components that run hotter than their class
[curves.sensor.lmsensors_mlx5_pci_0200_sensor0]
temp_low = 60
temp_high = 95

# Learned via calibration — duty % = expected RPM
[fans.FAN1]
zone = "cpu"

[fans.FAN1.setpoints]
25 = 320
30 = 450
40 = 620
50 = 780
100 = 1500

Use --config PATH with any command to specify an alternate config location.

Running on boot

TrueNAS SCALE's Init/Shutdown Scripts (under System > Advanced) run commands at boot and shutdown. Use tmux to run the daemon in a detachable session you can attach to later for debugging.

Add a script (Type: Command, When: Post Init):

tmux new-session -d -s truefan '/mnt/pool1/venvs/truefan/bin/truefan run 2>&1 | tee /var/log/truefan.log'

To check on the daemon: tmux attach -t truefan. Detach with Ctrl-b d.

How it works

Each sensor class has a temperature-to-duty curve. Between temp_low and temp_high, duty is linearly interpolated; hardware-reported thermal limits override temp_high when available. The hottest sensor in each fan zone sets the duty. A spindown window prevents rapid cycling.

If a fan stalls, the zone goes to 100% and the lowest setpoint is removed so the minimum duty rises going forward.

License

MIT