I could not get FAHControl to work!! I even created a fake Gnome-phython2 package based on one persons experiece on 19.04.
Some time ago I tried to get FAHControl going on another distribution at which FAHControl isn't supported (Gentoo Linux). I tried twice (but perhaps not very hard), and failed twice.
If you have a second computer which is able to run FAHControl (e.g. a Windows computer, or a Linux Mint computer), you can run FAHControl there and control FAHClient on the dGPU-equipped computer via your LAN. It is fairly easy to add another computer in FAHControl. One caveat: If the computer which is running FAHClient has got a "firewall" on it, you need to configure it to accept TCP traffic at port 36330
from the computer which runs FAHControl
to the computer which runs FAHClient.
As for FAHClient, the first part of
@biodoc's instructions should get you going on many Debian based distributions at least for the client.
I stopped the client, edited /etc/fahclient/config.xml to change <gpu v='false'/> to <gpu v='true'/>, then rebooted. I found that config.xml had been reset. I did chmod on the file to give rw permissions to the file before editing. The permissions had reverted as well.
If the client finds itself in various troublesome situations, it tends to rewrite config.xml.
For troubleshooting, you can also run FAHClient life in a console window, rather than as a background daemon:
sudo service FAHClient stop
— in case if it is currently running as a background service
sudo service FAHClient status
— just to check that it's down now
cd /var/lib/fahclient
— or wherever the data directory is on your computer
ls -la .
— just to check which user is owning the directory and its contents; usually the user is named "fahclient"
sudo -u fahclient FAHClient
— impersonate user "fahclient" (correct this for your system) and start FAHClient in the foreground
The terminal will now be occupied by FAHClient and show its log output, until FAHClient crashes or quits by itself, or you tell it to quit with
[Ctrl][c]
.