`prime-select intel` doesn't power off the NVIDIA GPU

Question

I have a Dell XPS 15 9560 laptop with an Nvidia GTX 1050 graphics card. I just installed Ubuntu 20.04 with nvidia-driver-440.

When I run prime-select intel and reboot, prime-select query prints intel as expected, but powertop shows the NVIDIA GPU running at 100%, and the laptop is hot. The same happens in on-demand mode.

The existing question's accepted answer is for Ubuntu 18.04 and doesn't fix my problem, since sudo tee /proc/acpi/bbswitch <<<OFF returns tee: /proc/acpi/bbswitch: No such file or directory.

How to power off the NVIDIA GPU, using the proprietary driver?

Answer 1

In order to run sudo tee /proc/acpi/bbswitch <<<OFF, you will first have to install bbswitch. You can do this on Ubuntu 20 with

sudo apt install bbswitch-dkms

Followed by a reboot of your system.

If it still doesn't work, try running

sudo tee /etc/modules-load.d/bbswitch.conf <<<bbswitch

And then reboot again (That modules-load line is to ensure that bbswitch is initialized on boot)

Warning: On some systems, bbswitch crashes the computer on boot, giving you a black screen. From grub, instead of pressing "enter" to select your OS, press "e" to edit the boot parameters. At the end of the line that starts with linux, append modprobe.blacklist=bbswitch. After reboot, sudo apt remove bbswitch-dkms. You'll likely have to give up trying to use bbswitch at this point.