grub2 isn't really fit in the best screen resolution that my laptop can support (1280 x 800).
How can I do this without using a third party application ?
To do this safely requires two steps.
Reboot and press and hold Shift to display your grub. Press
C to enter console mode. Then type (for Ubuntu versions before 18.04):
For Ubuntu 18.04 and later:
This will display various stuff how grub recognizes your display. At the bottom is "preferred mode" - in your case it should say 1280x800. Note down the value.
Note: sometimes, some buggy video cards incorrectly give Grub the wrong preferred resolution - if the preferred mode is much higher than you were expecting, then select the nearest mode in the list displayed that you were expecting.
Press Esc to return to grub and press Enter to boot.
Reach for your terminal and type
$ sudo nano /etc/default/grub
find the line
# and change
640x480 with the preferred mode you wrote down. E.g.:
save, then type
$ sudo update-grub
Note: the preferred mode has to be among those listed by vbeinfo. For example, if your preferred mode is 1920x1080 (a common 16x9 aspect ratio setting), your preferred mode is NOT supported by vbeinfo and may not work correctly. In fact, there do not seem to be any 16x9 modes supported by vbeinfo, as of Ubuntu 13.04. In that case you could try falling back to something common like 640x480, which, it seems most monitors support and vbeinfo supports. Also, not all the modes supported by vbeinfo are necessarily supported by your monitor and you may have to experiment.
I'm using Ubuntu 16.04 and things are a little different in the packaged version of Grub for me.
vbeinfo command does not exist.
videotest command which you can use to test a given resolution, e.g.
videotest 1280x1024. However, while this test worked for me, I could not then get back to the grub menu! So that's not quite as useful (unless anyone can explain how to escape the test.)
/etc/default/grub but the line you're looking for is now called
GRUB_GFXMODE. So un-comment and set that to your desired mode.
update-grub and reboot.
Easy to use Grub2 settings customizer. Go to "Preferences" -> "Appearance"