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Problem:

You have full disk encryption. By using discrete only graphics you cannot enter the decryption key in the fancy boot GUI.

Details

My laptop (lenovo p50) has a bios option to enable/disable nvidia optimus, in particular:

  • hybrid mode (intel/nvidia)
  • discrete mode (nvidia only)

Why you should use nvidia only?

Dual screen works like a charm. So far, I cannot get multi screen using nvidia, in hybrid mode. I end up with a stretched, useless, single screen which spans over the monitors.

Using the intel is not possible (or I’m ignoring how to do that) by using hdmi (on my previous laptop I got hdmi/vga. Intel was wired to the vga and it worked, but still, hdmi was wired to the nvidia).

 

Use scenarios

I want to use nvidia only when most of my work is done at the desk, using external monitors and I don’t care about power consumption.

I want to use hybrid mode (intel/nvidia) when I do care about power consumption, battery duration. Mostly because I’m travelling or so.

 

Solution:

The solution is pretty straightforward (source at the end of the post).

When I want to use nvidia only:

in this way I can enter the decryption key in the framebuffer

  1. edit /etc/default/grub
  2. set GRUB_CMDLINE_LINUX_DEFAULT=’nomodeset’
  3. grub-mkconfig -o /boot/grub/grub.cfg

 

When I want to go hybrid:

fancy gui comes back

  1. edit /etc/default/grub
  2. set GRUB_CMDLINE_LINUX_DEFAULT=’quiet splash’
  3. grub-mkconfig -o /boot/grub/grub.cfg

Note:

I want to run grub-mkconfig to make it persistent. I you want to switch from a mode to another once, you can just change that line at boot (by pressing e)

 

Source

https://forums.lenovo.com/t5/Linux-Discussion/External-Display-issue-with-P50-on-Linux/td-p/2263113