I imagine you are using grub2. If so, then looking inside my /etc/default/grub file, I see this...
# The resolution used on graphical terminal
# note that you can use only modes which your graphic card supports via VBE
# you can see them in real GRUB with the command `vbeinfo'
There are two ways to list your VBE supported modes. The first way is at the grub command line. So during startup, press "c" at the grub screen. Then at the grub command line, type
Or alternatively, if you have the hwinfo
package installed, then you can list your VBE supported modes at the normal terminal command line with
sudo hwinfo --framebuffer
Then finally, using one of the VBE supported modes, modify your /etc/default/grub file similar to the above. And then lastly, type in "sudo update-grub" or similar, to rebuild your grub configuration.
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