Skip to content

sys

Practical examples for interacting with Linux sysfs (/sys) to inspect and configure hardware at runtime

Print fan speed in rpm by using awk

$ awk 'NR==1{l=$0;next}{print l ": " $0 " RPM"}' /sys/class/hwmon/hwmon0/fan1_label /sys/class/hwmon/hwmon0/fan1_input
CPU Fan Speed: 2847 RPM

Print fan speed in rpm

sed 's/^/Fan Speed: /g' /sys/class/hwmon/hwmon0/fan1_input

Print module names of hwmon

grep -R . /sys/class/hwmon/hwmon*/name

Read CPU fan speed (rpm) via hp-wmi-sensors

cat /sys/class/hwmon/hwmon*/fan*_input 2>/dev/null

Example 2: Read CPU fan speed (rpm) via hp-wmi-sensors

d=$(for x in /sys/class/hwmon/hwmon*; do [ -f "$x/name" ] && [ "$(cat "$x/name")" = "hp_wmi_sensors" ] && echo "$x" && break; done)
cat "$d"/fan*_input

Find the hp-wmi-sensors hwmon directory

for d in /sys/class/hwmon/hwmon*; do
  [ -f "$d/name" ] && [ "$(cat "$d/name")" = "hp_wmi_sensors" ] && echo "$d"
done

Read cpu fan RPM (raw sysfs value)

HWMON=$(for d in /sys/class/hwmon/hwmon*; do
  [ -f "$d/name" ] && [ "$(cat "$d/name")" = "hp_wmi_sensors" ] && echo "$d" && break
done)

cat "$HWMON"/fan*_input

Read cpu fan RPM with a label and values

for f in "$HWMON"/fan*_input; do
  n=${f%_input}
  label_file="${n}_label"
  label=$( [ -f "$label_file" ] && cat "$label_file" || basename "$n" )
  printf "%s: %s RPM\n" "$label" "$(cat "$f")"
done

Print current cpu speed

cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_cur_freq

Set scaling governor to perfomance

echo "performance" |tee /sys/devices/system/cpu/cpufreq/policy*/scaling_governor

Bios data is stored in /dmi folder

cat /sys/class/dmi/id/bios_date

List monitors

ls -1 /sys/class/drm | grep -E 'eDP|LVDS|DP|HDMI'

Holds power_supply settings

ls -1 /sys/class/power_supply

List USB devices by Vendor ID

awk -vRS= '/Vendor=0a12/{print $0,"\n"}' /sys/kernel/debug/usb/devices

Read battery percentage (laptops only)

cat /sys/class/power_supply/BAT0/{energy_full,energy_full_design,cycle_count}

ACPI thermal zones (throttling triggers)

cat /sys/class/thermal/thermal_zone*/{type,temp,trip_point_*}

Show temperatures of cpu

ls /sys/class/hwmon
cat /sys/class/hwmon/hwmon*/name
cat /sys/class/hwmon/hwmon*/temp*_input
cat /sys/class/hwmon/hwmon*/fan*_input

Read numa nodes and memory

cat /sys/devices/system/node/node*/meminfo

Read USB power / autosuspend

cat /sys/bus/usb/devices/*/power/{control,autosuspend}

USB descriptors (raw data)

cat /sys/bus/usb/devices/*/descriptors | hexdump -C

Read conneted monitors

cat /sys/class/drm/*/status

Read data about drives

ls /sys/block
cat /sys/block/sda/queue/{scheduler,rotational,read_ahead_kb}

I/O-statistik per drive

cat /sys/block/sda/stat

DebugFS mount (a lot of extra data)

mount | grep debugfs
ls /sys/kernel/debug

cpu scaling

cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq
cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq

Find network devices

for i in /sys/class/net/*; do
  printf "%s\n" "$(basename "$i")"
  ls -l "$i" | sed 's/^/└── /'
done

Set ENERGY_PERF_BIAS, 0 is highest perfomance and 15 is lowest

cat /sys/devices/system/cpu/cpu*/power/energy_perf_bias

Print scaling_driver in use

$ grep . /sys/devices/system/cpu/cpufreq/policy*/scaling_driver
/sys/devices/system/cpu/cpufreq/policy0/scaling_driver:intel_pstate
/sys/devices/system/cpu/cpufreq/policy1/scaling_driver:intel_pstate
/sys/devices/system/cpu/cpufreq/policy2/scaling_driver:intel_pstate
/sys/devices/system/cpu/cpufreq/policy3/scaling_driver:intel_pstate

Print scaling_available_governors info

cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_available_governors

Print mac address for eno1

cat /sys/class/net/eno1/address

Print speed of network interface

cat /sys/class/net/eno1/speed

Print cpu temperature in celsius by reading temp file (posix compatible)

while read -r t; do
  printf "%.2f°C\n" "$(echo "$t/1000" | bc -l)"
done < /sys/class/thermal/*/temp

Print cpu temperature in celsius by using awk

awk '{ printf "%.2f°C\n", $1/1000 }' /sys/class/thermal/*/temp

List all available display resolutions (per monitor via DRM)

cat /sys/class/drm/card0-DP-3/modes
cat /sys/class/drm/card0-HDMI-A-2/modes
cat /sys/class/drm/card0-DP-1/modes

Resource(s)