I have installed Ubuntu server 10.04.4 on VirtualBox but the screen appear too small. I read some guides that i have to change settings in grub to change the screen size, so i go to /etc/default/grub, opened grub in editor and edited this line #GRUB_GFXMODE=640x480 to GRUB_GFXMODE=1280x760. This is a resolution that my video card supports.
Then i updated grub and restarted the machine but it didn't work. When the machine starts loading in the beginning for a few seconds it goes into the screen resolution i have set but then goes back to the initial small screen resolution.
Any idea why it doesn't work?
Please elaborate are you talking about X11 server in the VM or about terminal fonts? In the former case you will need usual VBox Guest Extensions / DKMS, in the latter it heavily depends on text console management commands. I doubt that grub text console settings persist into login session, especially after this stuff with Plymouth et al.
There is no need to run commands nor install guest additions. I just hit shift+ctrl+c so it takes the guest host to scale mode, and then you can adjust the scale factor from settings display and adjust it for larger.