1FANCONTROL(8) System Manager's Manual FANCONTROL(8)
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6 fancontrol - automated software based fan speed regulation
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10 fancontrol [configfile]
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14 fancontrol is a shell script for use with lm_sensors. It reads its con‐
15 figuration from a file, then calculates fan speeds from temperatures
16 and sets the corresponding PWM outputs to the computed values.
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20 Please be careful when using the fan control features of your main‐
21 board, in addition to the risk of burning your CPU, at higher tempera‐
22 tures there will be a higher wearout of your other hardware components,
23 too. So if you plan to use these components in 50 years, maybe you
24 shouldn't use fancontrol at all. Also please keep in mind most fans
25 aren't designed to be powered by a PWMed voltage.
26 In practice it doesn't seem to be a major issue, the fans will get
28 slightly warmer, just be sure to have a temperature alarm and/or shut‐
29 down call, in case some fan fails, because you probably won't hear it
30 anymore ;)
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34 For easy configuration, there's a script named pwmconfig(8) which lets
35 you interactively write your configuration file for fancontrol. Alter‐
36 natively you can write this file yourself using the information from
37 this manpage.
38 Since most of you are going to use pwmconfig(8) script, the config file
40 syntax will be discussed last. First I'm going to describe the various
41 variables available for changing fancontrol's behaviour:
42 INTERVAL
45 This variable defines at which interval in seconds the main loop
46 of fancontrol will be executed
47 FCTEMPS
49 Maps PWM outputs to temperature sensors so fancontrol knows
50 which temperature sensors should be used for calculation of new
51 values for the corresponding PWM outputs.
52 FCFANS FCFANS records the association between a PWM and a fan. Then
54 fancontrol can check the fan speed and restart it if it stops
55 unexpectedly.
56 MINTEMP
58 The temperature below which the fan gets switched to minimum
59 speed.
60 MAXTEMP
62 The temperature over which the fan gets switched to maximum
63 speed.
64 MINSTART
66 Sets the minimum speed at which the fan begins spinning. You
67 should use a safe value to be sure it works, even when the fan
68 gets old.
69 MINSTOP
71 The minimum speed at which the fan still spins. Use a safe value
72 here, too.
73 MINPWM The PWM value to use when the temperature is below MINTEMP.
75 Typically, this will be either 0 if it is OK for the fan to
76 plain stop, or the same value as MINSTOP if you don't want the
77 fan to ever stop. If this value isn't defined, it defaults to 0
78 (stopped fan).
79 MAXPWM The PWM value to use when the temperature is over MAXTEMP. If
81 this value isn't defined, it defaults to 255 (full speed).
82 The configuration file format is a bit strange:
84 VARIABLE=chip/pwmdev=value chip/pwmdev2=value2
86 VARIABLE2=...
87 Each variable has its own line. The variable name is followed by an
89 equal sign and the device=value pairs. These consist of the relative
90 path to the pwm output (from /proc/sys/dev/sensors,
91 /sys/bus/i2c/devices or /sys/class/hwmon depending on the kernel ver‐
92 sion) for which the value is valid, equal sign followed by the value
93 and are separated by a blank. Example:
94 MINTEMP=w83627hf-isa-0290/pwm2=40 w83627hf-isa-0290/pwm1=54
96 You have to play with the temperature values a bit to get happy. For
98 initial setup I recommend using the pwmconfig script. Small changes can
99 be made by editing the config file directly following the rules above.
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103 fancontrol first reads its configuration, writes it to arrays and loops
104 its main function. This function gets the temperatures and fanspeeds
105 from kernel driver files and calculates new speeds depending on temper‐
106 ature changes, but only if the temp is between MINTEMP and MAXTEMP.
107 After that, the new values are written to the PWM outputs. Currently
108 the speed increases quadratically with rising temperature. This way you
109 won't hear your fans most of the time at best.
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113 lm_sensors-2.x
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117 pwmconfig(8), sensors(1).
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121 Marius Reiner <marius.reiner@hdev.de>
122 June 2007 FANCONTROL(8)