Thinkfan is a great piece of software, allowing the user to control fan behavior. It is primarily designed for laptops to ensure low noise operation and longer battery life.
Thinkfan configuration file (/etc/thinkfan.conf on debian-based GNU/Linux distros like Ubuntu) is rather straightforward to setup, details are available on this blog post.
However since a recent version of thinkpad-acpi kernel module, the old and deprecated interface /proc/acpi/ibm/thermal was removed. This change was not ported to thinkfan default configuration on Ubuntu 14.10 and I assume to the upstream code as well.
I will report a bug to both projects, but in the meantime, you can update thinkfan configuration file with the following:
# Path could differs
hwmon /sys/devices/platform/coretemp.0/hwmon/hwmon1/temp1_input (0)
hwmon /sys/devices/platform/coretemp.0/hwmon/hwmon1/temp2_input (0)
hwmon /sys/devices/platform/coretemp.0/hwmon/hwmon1/temp3_input (0)
# Settings for a T420s w/ Intel Sandy Bridge CPU
(0, 0, 40)
(1, 35, 70)
(2, 65, 80)
(5, 75, 128)
That’s all folks!
BTW, the Lenovo Thinkpad T420s is the perfect laptop. Actually, my only regrets are my 4 former laptops… If only I had known:)