1. Purpose

This document explains how to collect InfiniBand (IB) transceiver (QSFP module) temperature from servers using the Linux sysfs hwmon interface without requiring root privileges.

This method applies to systems using Mellanox / NVIDIA mlx5-based adapters (e.g., ConnectX series).

2. Scope

• HGX Nodes

• Management Nodes

• Any server with mlx5_* IB devices

Works when:

• Root access is not available

• Only temperature verification is required

3. Prerequisites

• SSH access to the server

• IB driver loaded (mlx5_core)

• /sys/class/infiniband/ available

Verify IB devices:

ls /sys/class/infiniband/

Expected output:

mlx5_0  mlx5_1  mlx5_2  ...

4. Collect Transceiver Temperature (Single Device)

Example for mlx5_0:

cat /sys/class/infiniband/mlx5_0/device/hwmon/hwmon*/temp*_label
cat /sys/class/infiniband/mlx5_0/device/hwmon/hwmon*/temp*_input

Sample Output

asic
Module0
65000
62000

Interpretation

• asic → HCA chip temperature

• Module0 / Module1 → Transceiver temperature

• Values are in millidegree Celsius

Convert:

62000 = 62°C

5. Collect From All IB Interfaces with Timestamp

echo "===== IB Temperature Snapshot ====="
date
for i in /sys/class/infiniband/mlx5_*; do
  echo "===== $i ====="
  paste \
    <(cat $i/device/hwmon/hwmon*/temp*_label) \
    <(cat $i/device/hwmon/hwmon*/temp*_input 2>/dev/null)
  echo ""
done

To save to file:

(echo "===== IB Temperature Snapshot ====="
date
for i in /sys/class/infiniband/mlx5_*; do
  echo "===== $i ====="
  paste \
    <(cat $i/device/hwmon/hwmon*/temp*_label) \
    <(cat $i/device/hwmon/hwmon*/temp*_input 2>/dev/null)
  echo ""
done
) > <hostname>_ib_temp_$(date +%F_%H-%M-%S).log

7. Temperature Threshold Reference

If transceiver temperature exceeds 75°C:

• Check airflow

• Check fan speed

• Verify BMC sensor status

• Escalate if persistent