After recently re-applying better thermal paste for the GPD Pocket 2, I wanted to also be able to keep an eye on system temperatures while running Ubuntu. Fortunately there is a pretty easy app for that, that you can use regardless of what machine you're running Ubuntu on. This application is called Psensor.
While there are probably other apps out there, this one seems to be fairly easy to use, and while its graph does not always seem to instantly update, it has a handy option where you can show the current temperature of your sensor of choice in the menubar.
I recommend you also install
lm-sensors, and possibly
hddtemp too if you need this. These both provide temperature readings to psensor.
sudo apt install lm-sensors hddtemp psensor
After installing these packages, launch psensors, it should show a list of all sensors it can find/access right away. On my machine it seemed to have an issue with showing the graph section, somehow hiding it completely every now and then, so if that happens for you too, try dragging the list of sensors from the left-most side. The screen should sort of split out into two sections, with the left section exposing the graph.
Showing a temperature reading in the menubar
To enable this, click the menubar icon, followed by
Sensor Preferences. Now select the sensor whose readings you'd like to show in the menubar from the list on the left, then click the
Application Indicator tab, and enable
Display sensor in the label (experimental). You can show multiple sensors' temperature readings in the menubar, which can be quite handy if you'd like to keep an eye on several parts of your system.
Launch at login
To automatically have psensors launch at login, click the menubar icon and click
Preferences. Then, under
Launch on session startup. I personally also enabled
Hide window on startup so that it won't get in the way, but I do get the sensor icon in my menubar.
The application also supports sending desktop notifications for sensors you select, and with thresholds you specify. To do this, click the menubar icon and click on
Sensor Preferences. Now select the sensor you'd like to create an alert for from the list on the left, and click on the
Alarm tab. Enable the
Activate desktop notifications checkbox, and set your desired high and optionally low thresholds. You can do this for multiple sensors, too.
That's all there is to it. You can now monitor your system temperatures from within Ubuntu. This is especially useful on mobile devices like the GPD Pocket 2, so you can comfortably turn its fan off and, should your system reach higher temperatures, you can simply re-enable the fan and have it cool down. Pretty nice.