Lenovo ThinkPad T420
This article covers the installation and configuration of Arch Linux on a Lenovo T420 laptop.
- 1 Installation
- 2 Hardware
- 3 Laptop Settings
- 4 Troubleshooting
- 5 See also
This laptop supports UEFI as well as the traditional BIOS.
There are no issues with installing Arch Linux with the latest Archiso.
The rest of the installation process can be followed with the Installation guide.
All hardware works out of the box except the following:
Fingerprint reader works great with fprint and PAM (installation of fingerprint-gui recommended).
Some Media keys
- See Media Keys
ACPI is well supported here. No obvious troubleshoots.
Unfortunately, tp_smapi is only partially supported on the Thinkpad T420. A number of features work since version 0.41. For example, the hard drive protection mechanism HDAPS now works well. See the linked wiki entry.
Some features like setting the starting threshold for charging the battery do not yet work. To control the battery charging thresholds, install the Perl script AUR.AUR from the
acpi_call kernel module by running
Manually set the thresholds by calling
/usr/bin/perl /usr/bin/tpacpi-bat -v -s SP 0 80 /usr/bin/perl /usr/bin/tpacpi-bat -v -s ST 0 40
The example values 40 and 80 given here represent the percentage of full battery capacity remaining. Adjust them to your own needs. You may also want to write a simple
set-battery.service and enable it to set them at startup. While these values should be permanent, they will be reset any time the battery is removed.
[Unit] Description=Set battery capacity [Service] Type=oneshot ExecStart=/usr/bin/perl /usr/bin/tpacpi-bat -v -s SP 0 80 ExecStart=/usr/bin/perl /usr/bin/tpacpi-bat -v -s ST 0 40 [Install] WantedBy=multi-user.target
Also, if you are dual booting with Windows, you can still control the battery charging thresholds with Lenovo's Power Manager which communicates directly to the battery controller.
When using systemd, you may want to blacklist the tp_smapi module if your systemd-modules-load.service fails, as new ThinkPads handle everything over acpi.
CPU frequency scaling
CPU frequency scaling is fully supported with all of the available processor models with this laptop.
Install the package
Copy the example sensor settings file from "/usr/share/doc/thinkfan/examples/thinkfan.conf.simple" to "/etc/thinkfan.conf".
# cp /usr/share/doc/thinkfan/examples/thinkfan.conf.simple /etc/thinkfan.conf
Aftwards replace the default
hwmon in the settings file
/etc/thinkfan.conf with the following:
Alternatively, sensors can be generated using following command. Add
hwmon before the sensor lines.
find /sys/devices -type f -name "temp*_input"
In the same configuration file replace the default fan level settings with your needs (the last lines of the file). Useful values are
(0, 0, 42) (1, 40, 47) (2, 45, 52) (3, 50, 57) (4, 55, 62) (5, 60, 67) (6, 65, 72) (7, 70, 77) (127, 75, 32767)
Finally enable the thinkfan service.
# systemctl enable thinkfan
Laptop Mode Tools
No significant issues were found using Laptop Mode Tools.
Possible bug with #Shutdown on battery.
The packageis an alternative tool that can replace AUR.
TouchPad and TrackPoint do work out of the box, but the TrackPoint is way too sensitive (i.e. fast) to be usable, since it is recognized as a mouse. Configure both devices as described in Touchpad Synaptics and TrackPoint.
To adjust the speed/sensitivity of the TrackPoint add these lines in a systemd tmpfile:
w /sys/devices/platform/i8042/serio1/speed - - - - 180 w /sys/devices/platform/i8042/serio1/sensitivity - - - - 200
Possible range of values are 1-255.
Alternatively, you can add an udev rule:
Bumblebee works as intended on models with NVIDIA Optimus
Optional kernel boot arguments
Using the following kernel boot parameters reduces battery drain:
i915.i915_enable_rc6=1 i915.i915_enable_fbc=1 i915.lvds_downclock=1 i915.semaphores=1
Media keys that (should) work out of the box:
- Wireless On/Off
- Backlight Brightness settings
- Microphone mute
Media Keys that Do Not work out of the box:
You must find a workaround and bind the keys yourself for the rest of them.
xbindkeys and AUR can be a solution for media keys that are not working. This solution also allows you to rebind the ThinkVantage button and certain FN layer shortcuts (the blue logos on the keyboard).
Rebind Forward and Back keys
Keys forward and back (next to cursor keys) can be easily remapped to PageDown/PageUp.
Install xmodmap with the package
~/.Xmodmap file with content:
keysym XF86Back = Page_Up keysym XF86Forward = Page_Down
Add this line to your
~/.xinitrc to make it work:
You can also re-map AudioPrev (
Fn+Left) and AudioNext (
Fn+Right) to Home/End:
keysym XF86AudioNext = End keysym XF86AudioPrev = Home
Turn touchpad on and off
For some, the (
Fn+F8) key does not switch the touchpad on and off. See Touchpad Synaptics#Software toggle for a workaround.
Volume up/down not changing volume
Shutdown on battery
Some users have reported that the T420 was rebooting on shutdown on battery power. There have been quite a few attempts to fix this. Three are detailed here.
One way is to disable the module
ehci_hcd. See Kernel modules#Blacklisting for more information.
Or try disable Laptop-mode.
!laptop-mode to the
DAEMONS array in
This forum post details another way to have your computer not reboot on shutdown. Turning off the
laptop-mode daemon causes battery life to suffer, so when on the move and in need of a simple way to shutdown, this seems to work better.
Hang on reboot
This is a problem on many laptops and can be fixed by blacklisting the
e1000e kernel module.