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Managing Supermicro Temps/Fans

Fan control and IPMI configuration for server motherboards running Linux. Tested on Supermicro H13-series (H13SSL-N, H13SSL-NT) but extensible to other boards and sensors via the Hardware and Sensor protocols.

example

Contents

  • fan-control.sh - Manual fan speed control
  • fan-daemon.py - Automatic temperature-based fan control daemon
  • visualize-temps.py - Temperature log visualization and plotting
  • lshw.sh - Hardware inventory script
  • setup-fan-daemon.sh - Install/uninstall the daemon as a systemd service
  • setup-ipmi-access.sh - Configure unprivileged IPMI access
  • setup-ipmi-limits.sh - Disable low-RPM alarms and set sensor thresholds

Features

Manual control - fan-control.sh provides simple per-zone fan speed control via IPMI raw commands. Set exact percentages or switch between BMC modes.

Automatic daemon - fan-daemon.py monitors temperatures and adjusts fan speeds using piecewise-constant curves with configurable thresholds.

  • Multi-zone: Different curves for case fans (zone 0) vs GPU fans (zone 1). One device can drive multiple zones with different curves.
  • Dual hysteresis: Temperature hysteresis (deadband) prevents oscillation at thresholds. Time hysteresis (min hold) requires temps to stay low before dropping speed, handling bursty workloads.
  • Extensible sensors: Sensor protocol for CPU (k10temp), GPU (nvidia-smi), NVMe (nvme-cli), HDD (smartctl), and IPMI (ipmitool). Add new sensors by implementing get().
  • Modular hardware: Hardware protocol abstracts board-specific IPMI commands. Port to other boards by implementing the interface.
  • Fail-safe: Any error sets fans to 100%.

Visualization - visualize-temps.py scrapes journalctl logs, stores data in npz, and generates temperature/fan speed plots for tuning curves.

Quick Start

git clone https://github.com/jvdillon/supermicro-h13-linux.git
cd supermicro-h13-linux

# Setup unprivileged IPMI access (log out/in after)
sudo ./setup-ipmi-access.sh

# Disable low-RPM fan alarms
sudo ./setup-ipmi-limits.sh

# Install the automatic fan control daemon
sudo ./setup-fan-daemon.sh install  # Or install-dev

# Monitor the daemon
journalctl -u fan-daemon -f

Fan Daemon

The fan-daemon.py script provides automatic temperature-based fan control. It reads temperatures from CPU, GPU, RAM, HDD, and NVMe devices and adjusts fan speeds using piecewise-constant curves with hysteresis.

Features

  • Per-device-type temperature mappings (CPU, GPU, RAM, HDD, NVMe)
  • Two-zone control (zone 0: FAN1-4, zone 1: FANA-B)
  • Hysteresis to prevent oscillation at threshold boundaries
  • Fail-safe: any error sets fans to 100%
  • GPU temps via nvidia-smi (IPMI available via --ipmi-temps)

Installation

sudo ./setup-fan-daemon.sh install      # Install and start (copies daemon)
sudo ./setup-fan-daemon.sh install-dev  # Install with symlink (for development)
sudo ./setup-fan-daemon.sh uninstall    # Stop and remove
sudo ./setup-fan-daemon.sh status       # Show status and logs

Configuration

View options:

./fan-daemon.py --help

Override temperature mappings via command line:

# Format: DEVICE[N][-zone[M]]=TEMP:SPEED[:HYST_C[:HYST_S]],...
# HYST_C = temp hysteresis (C), HYST_S = time hysteresis (s)
# Empty value uses default: 70:80::60 = default temp hyst, 60s time hyst
--speeds gpu=50:20,70:50,85:100           # All GPUs, all zones
--speeds gpu0-zone1=60:30,80:100          # GPU 0, zone 1 only
--speeds gpu=70:80:5:30                   # 5C temp hyst, 30s time hyst
--speeds hdd=                             # Disable HDD control

To modify the installed service:

sudo systemctl edit fan-daemon --full

Dependencies

sudo apt install ipmitool smartmontools nvme-cli
# nvidia driver required for GPU temp monitoring

Monitoring

journalctl -u fan-daemon -f

Output shows zone speeds, per-device temps, and which device triggered each zone:

INFO: z0=40% z1=100%
      cpu0         45C  z0:15%
      ram0         38C  z0:15%
      ram1         35C  z0:15%
      nvme0        42C  z0:15%
      hdd0         32C  z0:15%
      gpu0         72C  z0:40%  z1:100%  <-- z0,z1
      gpu1         70C  z0:40%  z1:100%
      gpu_ipmi0    73C
      vrm_cpu0     42C

For historical visualization and curve tuning, use visualize-temps.py:

./visualize-temps.py                    # Scrape logs, save to results/temps.npz, plot
./visualize-temps.py --since "2 hours"  # Limit time range
./visualize-temps.py --no-plot          # Just scrape and save data

Manual Fan Control

The fan-control.sh script provides manual fan speed control via IPMI.

Fan Zones

Zone Headers Typical Use
0 FAN1-4 CPU cooler, case intake/exhaust
1 FANA-B Auxiliary (GPU/peripheral)

Usage

# Show current status
./fan-control.sh status

# Set zone to specific percentage (15-100%)
./fan-control.sh 0 50      # Zone 0 to 50%
./fan-control.sh 1 40      # Zone 1 to 40%
./fan-control.sh all 60    # Both zones to 60%

# Switch to BMC-controlled modes
./fan-control.sh optimal   # Optimal (auto)
./fan-control.sh standard  # Standard
./fan-control.sh heavyio   # Heavy IO
./fan-control.sh full      # Full speed

Notes:

  • Minimum speed is 15%
  • Manual percentages require "full" mode (set automatically)
  • Use optimal to return to automatic BMC control

IPMI Access Setup

By default, /dev/ipmi* devices require root. Run once:

sudo ./setup-ipmi-access.sh
# Log out and back in

This creates an ipmi group, loads kernel modules, and sets udev rules.

To add other users:

sudo usermod -aG ipmi USERNAME

Sensor Thresholds

Factory fan thresholds trigger alarms at 420 RPM. For quiet operation:

sudo ./setup-ipmi-limits.sh

This disables low-RPM alarms. Run once after BMC reset.

Hardware Inventory

./lshw.sh              # Full hardware details
./lshw.sh --noserial   # Hide serial numbers (for sharing)

IPMI Raw Commands Reference

The following IPMI raw commands are derived from smfc.

# Get current mode (00=standard, 01=full, 02=optimal, 04=heavyio)
ipmitool raw 0x30 0x45 0x00

# Set mode
ipmitool raw 0x30 0x45 0x01 0x00  # standard
ipmitool raw 0x30 0x45 0x01 0x01  # full (required for manual control)
ipmitool raw 0x30 0x45 0x01 0x02  # optimal
ipmitool raw 0x30 0x45 0x01 0x04  # heavyio

# Get zone duty cycle (returns hex percentage)
ipmitool raw 0x30 0x70 0x66 0x00 0x00  # Zone 0
ipmitool raw 0x30 0x70 0x66 0x00 0x01  # Zone 1

# Set zone duty cycle (0x00-0x64 = 0-100%)
ipmitool raw 0x30 0x70 0x66 0x01 0x00 0x32  # Zone 0 to 50%
ipmitool raw 0x30 0x70 0x66 0x01 0x01 0x28  # Zone 1 to 40%

Tested Configuration

Component Model
Motherboard Supermicro H13SSL-N
CPU AMD EPYC 9555 (Turin/Zen 5)
RAM 4x32GB DDR5-5600 ECC (SK Hynix)
GPU 2x NVIDIA GeForce RTX 5090
NVMe WD Black SN8100 4TB
HDD Seagate IronWolf Pro 12TB
PSU Seasonic PRIME PX-1600 (1600W Platinum)
Case Phanteks Enthoo Pro 2 Server Edition
CPU Cooler ARCTIC Freezer 4U-SP5
Case Fans ARCTIC P14 Pro PST
GPU Fans ARCTIC P12 Slim PWM PST
OS Ubuntu 24.04 LTS

This project should work out-of-the-box on other H13-series boards with similar BMC firmware. Other boards and sensors can be supported by implementing the Hardware and Sensor protocols.

Why not smfc?

smfc is a mature fan control solution for Supermicro boards and an excellent project.

We opted to write our own because of the need for a fundamentally different control loop architecture. The key difference is zone overlap: for example, our GPUs drive both case fans (zone 0, gentle curve) and GPU-specific fans (zone 1, aggressive curve) simultaneously. smfc's architecture requires one controller per zone with no overlap. This difference makes sense because smfc appears to be written more with HDD in mind than GPU, the latter having significant case-wide temperature implications.

Summary of differences:

Feature fan-daemon smfc
Device multizone One device can drive multiple zones Each controller owns one zone, no overlap
Zone arbitration Max speed wins across all devices per zone N/A (single controller per zone)
Curves Piecewise-constant with arbitrary breakpoints Linear min/max interpolation
Temp hysteresis Deadband Deadband (aka "Sensitivity")
Time hysteresis Min hold: temp must stay low for N seconds (true hysteresis) Delay after speed change
Config CLI flags with sensible defaults INI config file required
Complexity ~1100 lines ~3500 lines
Hardware abstraction Hardware protocol for easy porting Supermicro-specific
Sensor abstraction Sensor protocol for easy extension Hardcoded sensor types
Sensor merging Logical devices (keys) from multiple physical sensors Fixed sensor per device type
Python Typed (passes pyright strict) Untyped

We support either using IPMI (BMC) for temps or device specific tools (coretemp/k10temp, nvidia-smi, smartctl, nvme-cli, etc). Although BMC is the authority on server boards (such as the H13)--it is slow and prone to race conditions. By default we use the most specific sensor reader we can, but offer an ipmitool-based sensor and a clean mechanism for merging sensors.

The Hardware protocol abstracts board-specific IPMI commands, so adding support for other motherboards is straightforward--just implement the interface (get_temps, set_zone_speed, etc.).

Acknowledgments

IPMI raw commands derived from smfc.

License

Apache 2.0

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Fan control for Supermicro motherboards.

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