That will give you a better quality picture and your fonts will appear smaller so you'll be able to see a lot more of your boot entries on the screen without scrolling so much.
1. If you don't already know what resolutions your video hardware can support, you can boot GRUB2 and press 'C' fro your GRUB Menu to go into into CLI Mode GRUB . Then you can run the vbeinfo command for a list of resolutions your hardware can support. Press your pause key if you need more time to read the text.
2. Write the numbers down on a piece of scrap paper if you need to.
3. Open your /etc/default/grub file with a text editor and change your settings there
|gksudo gedit /etc/default/grub|
4. Alter the numbers after where it says"GRUB_GFXMODE=" with a suitable resolution for your hardware,
|# If you change this file, run 'update-grub' afterwards to update|
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
# Uncomment to disable graphical terminal (grub-pc only)
# 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'
# Uncomment if you don't want GRUB to pass "root=UUID=xxx" parameter to Linux
# Uncomment to disable generation of recovery mode menu entrys
4. Save the file before closing it.
5. Run sudo grub-mkconfig to write the changes to your grub.cfg,
|sudo grub-mkconfig -o /boot/grub/grub.cfg|
6. reboot and see if it worked.