shushmyipmi

Dynamic IPMI fan control daemon for Supermicro servers.

Replaces the BMC's aggressive default fan curve with a smooth thermal ramp, keeping the system quiet at idle while still responding to real load.

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Background

Supermicro 1U servers ship with BMC fan control tuned for worst-case datacenter environments. At idle or light load in a home lab or office, the result is ear-splitting fan noise. This daemon wraps ipmitool to assert a custom thermal curve, detect and correct BMC overrides, and stay out of the way when things actually get hot.

Developed and tested on:

• Board: Supermicro X10DRU (dual socket Xeon E5 v4), 1U, 2 fan zones
  • OS: Ubuntu 24.04
  • GPU: Intel Arc Pro B50
• Board: Supermicro X11DPG-OT (SYS-4029GP-TRT, dual socket, GPU chassis), 4U, 4 fan zones
  • OS: Ubuntu 26.04
  • GPU: none yet (Intel, planned)

May work on other X10/X11-series boards. Zone count and idle floors vary by chassis — see FAN_ZONES in Configuration below. X9 boards use a different IPMI raw command scale (0x00–0xff) and will need adjustments.

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How it works

< 50°C   →  fans at minimum speed (floor)
50–70°C  →  linear interpolation, min → max speed
>= 70°C  →  panic mode: step up aggressively every interval

The BMC is not disabled — it remains the thermal safety net. This daemon runs on top of it and corrects overrides every check interval. If the BMC slams fans to full due to a genuine thermal event, the daemon will detect it and only correct back down once temps are under control.

Important: Fan mode is set to Full (0x01) once at startup only. Issuing the mode command in a loop causes a momentary 100% fan spike every time — do not change this behavior.

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Requirements

• ipmitool
• python3
• IPMI kernel modules: ipmi_devintf, ipmi_si
• Root / sudo access

sudo apt install ipmitool python3

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Installation

# Copy script
sudo cp ipmi-fan-control.py /usr/local/bin/
sudo chmod +x /usr/local/bin/ipmi-fan-control.py

# Load IPMI modules at boot
echo -e "ipmi_devintf\nipmi_si" | sudo tee /etc/modules-load.d/ipmi.conf

# Install and enable service
sudo cp ipmi-fan-control.service /etc/systemd/system/
sudo systemctl daemon-reload
sudo systemctl enable --now ipmi-fan-control.service

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Configuration

All tunable values are at the top of ipmi-fan-control.py:

Variable	Default	Description
FAN_ZONES	[(0x00, 0x10), (0x01, 0x10)]	List of (zone_index, idle_floor) tuples. One entry per fan zone the BMC exposes — probe with ipmitool raw 0x30 0x70 0x66 0x00 <zone> per index before assuming only 2 zones exist (some 4U/GPU chassis expose 4). Each zone can have its own floor. MIN_SPEED is derived as the lowest floor across all zones.
MAX_SPEED	0x64	Fan ceiling, shared across all zones
RAMP_START_TEMP	50	°C where ramp begins
RAMP_END_TEMP	70	°C where ramp ends / panic begins
PANIC_TEMP	70	°C threshold for panic mode
STEP_UP	0x10	Speed increase per interval in panic mode
MAX_STEP_UP	0x08	Max speed increase per interval in ramp zone
DEADBAND	0x04	Minimum delta before issuing a new fan command
CHECK_INTERVAL	10	Seconds between checks

Speed values (hex)

%	Hex
10	0x0a
16	0x10
20	0x14
25	0x19
30	0x1e
40	0x28
50	0x32
60	0x3c
75	0x4b
100	0x64

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Monitoring

# Live logs
journalctl -fu ipmi-fan-control.service

# Current fan mode (should be 0x01 after startup)
sudo ipmitool raw 0x30 0x45 0x00

# Current fan duty cycle (zone 0)
sudo ipmitool raw 0x30 0x70 0x66 0x00 0x00

# CPU temps
sensors

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Troubleshooting

Fans spike to 100% on service restart Should not happen — ExecStartPre asserts Full mode and idle fan speeds directly (matching FAN_ZONES) before the daemon even starts, so the BMC never gets a window to apply its own loud default curve. If you change FAN_ZONES in the script, update the matching ipmitool lines in ipmi-fan-control.service too — they're not read from the script.

BMC override detected warnings in logs Expected occasionally. The BMC runs its own fan polling on a fixed schedule. The daemon detects and corrects these within one check interval.

ipmitool: Could not open device at /dev/ipmi0 IPMI kernel modules not loaded. Run:

sudo modprobe ipmi_devintf ipmi_si

And make sure /etc/modules-load.d/ipmi.conf exists (see Installation).

Script not executable

sudo chmod +x /usr/local/bin/ipmi-fan-control.py

Shebang must be line 1 If you edit the script, ensure #!/usr/bin/env python3 is the very first line. A comment before the shebang breaks execution (exit code 203).

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License

MIT