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

NAME

       fancontrol - automated software based fan speed regulation

SYNOPSIS

       fancontrol [configfile]

DESCRIPTION

       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.

WARNING

       Please be careful when using the fan control features of your mainboard, in addition to the risk of burning your CPU,  at  higher  tempera-
       tures  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  shut-
       down call, in case some fan fails, because you probably won't hear it anymore ;)

CONFIGURATION

       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 var-
       ious variables available for changing fancontrol's behaviour:

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

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

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

       FCTEMPS
	      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.

       MINTEMP
	      The temperature below which the fan gets switched to minimum speed.

       MAXTEMP
	      The temperature over which the fan gets switched to maximum speed.

       MINSTART
	      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.

       MINSTOP
	      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
	      VARIABLE2=...

       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.

THE ALGORITHM

       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 quadratically	with  rising  temperature.
       This way you won't hear your fans most of the time at best.

SEE ALSO

       pwmconfig(8), sensors(1).

AUTHOR

       Marius Reiner <marius.reiner@hdev.de>

lm-sensors 3							  September 2009						     FANCONTROL(8)