FANCONTROL(8)               System Manager's Manual              FANCONTROL(8)

       fancontrol - automated software based fan speed regulation

       fancontrol [configfile]

       fancontrol is a shell script for use with lm_sensors. It reads its
       configuration from a file, then calculates fan speeds from temperatures
       and sets the corresponding PWM outputs to the computed values.

       Please be careful when using the fan control features of your
       mainboard, in addition to the risk of burning your CPU, at higher
       temperatures there will be a higher wearout of your other hardware
       components, too. So if you plan to use these components in 50 years,
       maybe you shouldn't use fancontrol at all.  Also please keep in mind
       most fans aren't designed to be powered by a PWMed voltage.

       In practice it doesn't seem to be a major issue, the fans will get
       slightly warmer, just be sure to have a temperature alarm and/or
       shutdown call, in case some fan fails, because you probably won't hear
       it anymore ;)

       For easy configuration, there's a script named pwmconfig(8) which lets
       you interactively write your configuration file for fancontrol.
       Alternatively you can write this file yourself using the information
       from this manpage.

       Since most of you are going to use pwmconfig(8) script, the config file
       syntax will be discussed last. First I'm going to describe the various
       variables available for changing fancontrol's behaviour:

              This variable defines at which interval in seconds the main loop
              of fancontrol will be executed

              Maps hwmon class devices to physical devices. This lets
              fancontrol check that the configuration file is still up-to-

              Records hwmon class device names. This lets fancontrol check
              that the configuration file is still up-to-date.

              Maps PWM outputs to temperature sensors so fancontrol knows
              which temperature sensors should be used for calculation of new
              values for the corresponding PWM outputs.

       FCFANS Records the association between a PWM output and a fan input.
              Then fancontrol can check the fan speed and restart it if it
              stops unexpectedly.

              The temperature below which the fan gets switched to minimum

              The temperature over which the fan gets switched to maximum

              Sets the minimum speed at which the fan begins spinning. You
              should use a safe value to be sure it works, even when the fan
              gets old.

              The minimum speed at which the fan still spins. Use a safe value
              here, too.

       MINPWM The PWM value to use when the temperature is below MINTEMP.
              Typically, this will be either 0 if it is OK for the fan to
              plain stop, or the same value as MINSTOP if you don't want the
              fan to ever stop.  If this value isn't defined, it defaults to 0
              (stopped fan).

       MAXPWM The PWM value to use when the temperature is over MAXTEMP.  If
              this value isn't defined, it defaults to 255 (full speed).

       The configuration file format is a bit strange:

              VARIABLE=chip/pwmdev=value chip/pwmdev2=value2

       Each variable has its own line. The variable name is followed by an
       equal sign and the device=value pairs. These consist of the path to the
       pwm output for which the value is valid, equal sign followed by the
       value and are separated by a blank. Path can be absolute or relative
       (from /sys/bus/i2c/devices or /sys/class/hwmon depending on the kernel
       version). Example:

              MINTEMP=hwmon0/device/pwm1=40 hwmon0/device/pwm2=54

       You have to play with the temperature values a bit to get happy. For
       initial setup I recommend using the pwmconfig script. Small changes can
       be made by editing the config file directly following the rules above.

       Upon starting, fancontrol will make sure that all referenced devices do
       exist and match what they were at configuration time, and that all
       referenced sysfs files do exist. If not, it will quit immediately, upon
       the assumption that the configuration file may be out-of-sync with the
       loaded kernel drivers.

       fancontrol first reads its configuration, writes it to arrays and loops
       its main function.  This function gets the temperatures and fanspeeds
       from kernel driver files and calculates new speeds depending on
       temperature changes, but only if the temp is between MINTEMP and
       MAXTEMP. After that, the new values are written to the PWM outputs.
       Currently the speed increases linearly with rising temperature. This
       way you won't hear your fans most of the time at best.

       pwmconfig(8), sensors(1).

       Marius Reiner <>

lm-sensors 3                    September 2009                   FANCONTROL(8)