Linux: Dell Laptop Fan Control And Get CPU Temperature

1. Cpu temperature
2. Left or right fan status
3. Left or right fan speed
4. Ac power status
5. Fn buttons status

Say hello to i8k driver to control Dell laptop fan

You need to load a driver called i8k. It is used for accessing SMM BIOS on Dell laptops. It is well supported on business class Dell laptop modules such as Latitude, Inspiron, Vostro, Precision mobile workstations and so on. This module is included with Linux kernel version 3.0 or above.

How do I load the driver?

Type the following modprobe command to load the i8k driver:
$ sudo modprobe -v i8k
OR
# modprobe -v i8k
Here is what I see:

insmod /lib/modules/3.5.0-30-generic/kernel/drivers/char/i8k.ko

Install i8kutils package on Debian / Ubuntu

Open a terminal and then type the apt command/apt-get command:
$ sudo apt-get install i8kutils
Outputs:

[sudo] password for vivek: 
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following additional packages will be installed:
  acpi tcl tcl8.6
Suggested packages:
  tcl-tclreadline
The following NEW packages will be installed:
  acpi i8kutils tcl tcl8.6
0 upgraded, 4 newly installed, 0 to remove and 0 not upgraded.
Need to get 51.8 kB of archives.
After this operation, 181 kB of additional disk space will be used.
Do you want to continue? [Y/n] y
Get:1 http://archive.ubuntu.com/ubuntu focal/universe amd64 acpi amd64 1.7-1.1 [12.9 kB]
Get:2 http://archive.ubuntu.com/ubuntu focal/main amd64 tcl8.6 amd64 8.6.10+dfsg-1 [14.8 kB]
Get:3 http://archive.ubuntu.com/ubuntu focal/universe amd64 tcl amd64 8.6.9+1 [5,112 B]
Get:4 http://archive.ubuntu.com/ubuntu focal/universe amd64 i8kutils amd64 1.43 [19.0 kB]
Fetched 51.8 kB in 2s (31.4 kB/s)   
Selecting previously unselected package acpi.
(Reading database ... 293832 files and directories currently installed.)
Preparing to unpack .../acpi_1.7-1.1_amd64.deb ...
Unpacking acpi (1.7-1.1) ...
Selecting previously unselected package tcl8.6.
Preparing to unpack .../tcl8.6_8.6.10+dfsg-1_amd64.deb ...
Unpacking tcl8.6 (8.6.10+dfsg-1) ...
Selecting previously unselected package tcl.
Preparing to unpack .../archives/tcl_8.6.9+1_amd64.deb ...
Unpacking tcl (8.6.9+1) ...
Selecting previously unselected package i8kutils.
Preparing to unpack .../i8kutils_1.43_amd64.deb ...
Unpacking i8kutils (1.43) ...
Setting up tcl8.6 (8.6.10+dfsg-1) ...
Setting up acpi (1.7-1.1) ...
Setting up tcl (8.6.9+1) ...
Setting up i8kutils (1.43) ...
Created symlink /etc/systemd/system/multi-user.target.wants/i8kmon.service → /lib/systemd/system/i8kmon.service.
Processing triggers for man-db (2.9.1-1) ...
Processing triggers for systemd (245.4-4ubuntu3.2) ...

Older Linux distro config (pre systemd)

Edit the file /etc/default/i8kbuttons and /etc/default/i8kmon and set ENABLED to 1:

ENABLED=1

Alternatively, use the sed command to do all your dirty work:

sed -i.bak 's/ENABLED=0/ENABLED=1/' /etc/default/{i8kmon,i8kbuttons}

Start the service (this is equivalent of running the modprobe -v i8k command):
# /etc/init.d/i8kmon start
Sample outputs:

 * Starting Dell Inspiron fan/cpu-temperature monitor i8kmon             [ OK ] 

Newer Linux distro with systemd

You need to edit and check for the /etc/i8kmon.conf file using the vim command or cat command:
$ cat /etc/i8kmon.conf
Default config file:

# Sample i8kmon configuration file (/etc/i8kmon.conf, ~/.i8kmon).
 
# External program to control the fans
set config(i8kfan)	/usr/bin/i8kfan
 
# Report status on stdout, override with --verbose option
set config(verbose)	0
 
# Status check timeout (seconds), override with --timeout option
set config(timeout)	2
 
# Temperature threshold at which the temperature is displayed in red
set config(t_high)	80
 
# Temperature thresholds: {fan_speeds low_ac high_ac low_batt high_batt}
# These were tested on the I8000. If you have a different Dell laptop model
# you should check the BIOS temperature monitoring and set the appropriate
# thresholds here. In doubt start with low values and gradually rise them
# until the fans are not always on when the cpu is idle.
set config(0)   {{0 0}  -1  55  -1  60}
set config(1)   {{1 1}  50  65  55  70}
set config(2)   {{2 2}  60  75  65  80}
set config(3)   {{2 2}  70 128  75 128}
 
# Speed values are set here to avoid i8kmon probe them at every time it starts.
set status(leftspeed)	"0 1000 2000 3000"
set status(rightspeed)	"0 1000 2000 3000"
 
# end of file

Use the systemctl command to start/stop/restart the service:
$ sudo systemctl start i8kmon.service
$ sudo systemctl stop i8kmon.service
$ sudo systemctl restart i8kmon.service
$ sudo systemctl status i8kmon.service

How do I see the current status?

Type the following command
$ i8kctl
Here is what i see from my Dell laptop:

1.0 (null) XYZABC123 43 1 1 77130 78120 0 -1

Where,

1. 1.0 i8k format version
2. (null) bios version
3. XYZABC123 machine id (Dell serial number)
4. 43 cpu temperature
5. 1 left fan status
6. 1 right fan status
7. 7713 left fan speed
8. 7812 right fan speed
9. 0 ac power status
10. -1 : fn buttons status

Just print the CPU temp, enter:
$ i8kctl temp
Sample outputs:

52

Controlling fan speed on Dell laptop

First, just print the fan status info:
$ i8kctl fan
Sample outputs:

1 1

The fan command can accept two optional parameters which specify the new fan state for left and right fans. The state parameter can be:
Where,

1. 0 : turn the fan off (not recommended)
2. 1 : set low speed
3. 2 : set high speed
4. - : don’t change the state of this fan

For example, the following command sets the left fan (usually used by CPU) to high speed and leaves the right unchanged:
$ i8kctl fan 2 -
In this example, sets the left fan (usually used by CPU) to high speed and leaves the left unchanged:
$ i8kctl fan - 2
The following will set both fans to low speed:
$ i8kctl fan 1 1
This is equivalent of running the following commands:

 ## the syntax is ##
i8kfan leftFan rightFan
 
# Set left fan on high and leaves the right unchanged
i8kfan 2 -
 
# Set right fan on high and leaves the left unchanged
i8kfan - 2
 
# Set both fans to low 
i8kfan 1 1

Please note that the service /etc/init.d/i8kmon starts i8kmon in daemon mode. So setting the speed with i8kfan is pointless since the daemon will override the speed with its own value on fly as per system temperature.

Using sensors command

First, install and configure lm_sensors package as described here and type the following command to see information about your FAN and cpu core temperature:
$ sensors

sensors command in action – show the current readings of all sensor chips on Dell laptop

I also suggest that you use the acpi -V command to see the current battery status and thermal temperature under Linux operating systems.

Summing up

You learned about 98kfan command-line tility to access SMM BIOS and DMI table information from Dell laptops. See following docs for more info:

• Linux: Monitor hard disks temperature with hddtemp command.
• Linux Laptop: Display battery status and thermal temperature from command line.
• FreeBSD: Get / Read hard disk temperature using smartd.
• Monitoring hard disk health with smartd under Linux or UNIX operating systems.

Read i8kfan documentation by typing the following man command:
man i8kfan