Fixing tiny GRUB menu on 4K display

I bought a Gigabyte M27UP 4K display and the GRUB boot menu became unreadably tiny. Two lines in a config file sorts it out.

Edit /etc/default/grub and add:

GRUB_GFXMODE=800x600
GRUB_GFXPAYLOAD=keep
GRUB_TERMINAL=gfxterm

• GRUB_GFXMODE — sets the resolution of the GRUB menu. In this case, 800x600 is a safe choice that works on all displays. It is little bit bigger on 4K monitor but I’m fine with that.
• GRUB_GFXPAYLOAD — keep tells the kernel to keep the same video mode set by GRUB, avoiding a resolution flash during boot.
• GRUB_TERMINAL — switches GRUB to graphical terminal mode, which is required for GRUB_GFXMODE to take effect.

Then run:

sudo update-grub

Reboot and GRUB is readable again.