This post describes how to adapt the size of the Grub splash screen and the virtual terminal on Debian.
In the following, I will set both to the size of 1280 x 1024 pixels. This may not suit your installation. To be sure, install the tool hwinfo and check the available configurations:
sudo apt-get install hwinfo sudo hwinfo --framebuffer
Grub splash scren
Open /etc/default/grub (as root) and add/modify the following lines:
# in file /etc/default/grub GRUB_GFXMODE=1280x1024 GRUB_GFXPAYLOAD=1280x1024
Afterwards, update the grub configuration and reboot:
sudo update-grub2 sudo reboot
Now, the Grub splash screen appears larger, but the virtual console of Debian is still quite tiny.
Debian virtual console
For increasing the size of Debian’s virtual terminal, open /etc/default/grub, again and add the following line:
# in file /etc/default/grub GRUB_GFXPAYLOAD_LINUX=1280x1024x16
If this solution did not work for you, you may try other suggestions from this stackoverflow thread.