Preamble

#

I recently bought myself a Dell OptiPlex 5070 Micro to play with. It’s the first node of what will be a 3-node cluster that I will use to start playing with Kubernetes in the real (read: non-virtualised) world.

During the initial setup, I realised I couldn’t see the fan speed with the sensors utility from the lm-sensors Linux package.

After the usual sudo sensors-detect (I actually use sudo sensors-detect --auto because I like to live dangerously), I could see core temperatures and other sensor readings, but no fan speed.

Thanks to some great folks on Ask Ubuntu¹, I found the solution to this was very simple.

To read fan speeds, the i8k² kernel driver must be loaded. This driver provides access to the SMM BIOS, designed for Dell laptops, but it works with these machines too.

At first I tried sudo modprobe i8k, but received an error: could not insert 'dell_smm_hwmon': No such device

Oh well, hammer method it is I guess: sudo modprobe i8k force=1

And just like that, I can see fan speeds with sensors!

Solution

#

You will, of course, need the lm-sensors package.

I also strongly suggest running sudo sensors-detect. The default choices from this utility can be safely accepted if you’re unsure of anything.

For one-time usage, simply run this: sudo modprobe i8k force=1

If you wish to always load the driver at boot time, here’s how:

1. echo 'i8k' | sudo tee -a /etc/modules
   By adding the line i8k to /etc/modules, we instruct the system to load the module at boot time.
2. echo 'options i8k force=1' | sudo tee -a /etc/modprobe.d/i8k.conf
   By adding the line options i8k force=1 to /etc/modprobe.d/i8k.conf, we instruct the system which options to use when loading the module.
   You can name this whatever you like as long as it has a .conf extension.
3. Reboot to see the change.

You will now be able to view the fan speed with sensors.

Another useful tool

#

During my searches, I also found i8kutils, a package containing some utilities for controlling fans accessible by the i8k² driver.

I haven’t tested this on my OptiPlex 5070 Micro, but thought it worth sharing nevertheless.

There are some open issues in the i8kutils repository noting some bugs with the OptiPlex 5050, suggesting it at least partially works with this machine and others similar, and I’ve seen reports in various places of success with the OptiPlex 7060.