In the process of starting up an old computer I hadn’t used for 8 months (and for which I couldn’t remember the login without a considerable amount of trial and error), I stumbled upon a little note I had made for myself.
It’s an old Debian squeeze laptop, and after the initial install, the bootloader and terminal resolution was fairly low. The max resolution on this box is 1024×768 (wow!) so I wanted to take advantage of that. Basically, I just edited GRUB’s default configuration file. This is for GRUB version 2.
/etc/default/grub (using any plaintext editor) change
GRUB_GFXMODE to the desired resolution, such as:
The line needs to be uncommented by removing a potential
# sign at the start.
update-grub from the terminal and reboot. The boot menu and terminal should now be displayed in the new resolution. Remember to do both of these as root.