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]
11
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.
17
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 ;)
31
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 DEVPATH
49 Maps hwmon class devices to physical devices. This lets fancon‐
50 trol check that the configuration file is still up-to-date.
51 DEVNAME
53 Records hwmon class device names. This lets fancontrol check
54 that the configuration file is still up-to-date.
55 FCTEMPS
57 Maps PWM outputs to temperature sensors so fancontrol knows
58 which temperature sensors should be used for calculation of new
59 values for the corresponding PWM outputs.
60 FCFANS Records the association between a PWM output and a fan input.
62 Then fancontrol can check the fan speed and restart it if it
63 stops unexpectedly.
64 MINTEMP
66 The temperature below which the fan gets switched to minimum
67 speed.
68 MAXTEMP
70 The temperature over which the fan gets switched to maximum
71 speed.
72 MINSTART
74 Sets the minimum speed at which the fan begins spinning. You
75 should use a safe value to be sure it works, even when the fan
76 gets old.
77 MINSTOP
79 The minimum speed at which the fan still spins. Use a safe value
80 here, too.
81 MINPWM The PWM value to use when the temperature is below MINTEMP.
83 Typically, this will be either 0 if it is OK for the fan to
84 plain stop, or the same value as MINSTOP if you don't want the
85 fan to ever stop. If this value isn't defined, it defaults to 0
86 (stopped fan).
87 MAXPWM The PWM value to use when the temperature is over MAXTEMP. If
89 this value isn't defined, it defaults to 255 (full speed).
90 AVERAGE
92 How many last temperature readings are used to average the tem‐
93 perature. It can be used to smoothen short temperature peaks.
94 If this value isn't defined, it defaults to 1 (no averaging).
95 The configuration file format is a bit strange:
97 VARIABLE=chip/pwmdev=value chip/pwmdev2=value2
99 VARIABLE2=...
100 Each variable has its own line. The variable name is followed by an
102 equal sign and the device=value pairs. These consist of the path to the
103 pwm output for which the value is valid, equal sign followed by the
104 value and are separated by a blank. Path can be absolute or relative
105 (from /sys/bus/i2c/devices or /sys/class/hwmon depending on the kernel
106 version). Example:
107 MINTEMP=hwmon0/device/pwm1=40 hwmon0/device/pwm2=54
109 You have to play with the temperature values a bit to get happy. For
111 initial setup I recommend using the pwmconfig script. Small changes can
112 be made by editing the config file directly following the rules above.
113 Upon starting, fancontrol will make sure that all referenced devices do
115 exist and match what they were at configuration time, and that all ref‐
116 erenced sysfs files do exist. If not, it will quit immediately, upon
117 the assumption that the configuration file may be out-of-sync with the
118 loaded kernel drivers.
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122 fancontrol first reads its configuration, writes it to arrays and loops
123 its main function. This function gets the temperatures and fanspeeds
124 from kernel driver files and calculates new speeds depending on temper‐
125 ature changes, but only if the temp is between MINTEMP and MAXTEMP.
126 After that, the new values are written to the PWM outputs. Currently
127 the speed increases linearly with rising temperature. This way you
128 won't hear your fans most of the time at best.
129
132 pwmconfig(8), sensors(1).
133
136 Marius Reiner <marius.reiner@hdev.de>
137lm-sensors 3 September 2009 FANCONTROL(8)