change resolution of virtualbox

1. virtualbox 4.3.10 , Debian7.4(none desktop environment)

2. update grub to grub2

sudo apt-get install grub-pc

sudo upgrade-from-grub-legacy

3. Getting resolution from GRUB2.
    At grub menu list type "c" into command and input "vbeinfo" than you can get all resolution     providing by graphic card.
ex:1280x1024x16,800x600x24,640x480.....

3.modify /etc/default/grub

• GRUB_GFXMODE=1024x768x8

1024x768x8 => this value is got from Step 3.

• GRUB_GFXPAYLOAD_LINUX=keep

GRUB_GFXPAYLOAD_LINUX will work with  GRUB_GFXMODE.
It wil let kernel have the same resoluiton with GRUB2.

4.running sudo update-grub afterwards to update.

http://wiki.ubuntu-tw.org/index.php?title=GRUB2%E4%B8%AD%E6%96%87%E6%8C%87%E5%8D%97%E7%AC%AC%E4%BA%8C%E7%89%88(%E4%B8%8A%EF%BC%89

ps:
If  want to get more resolution setting vale , you can use followed command.

VBoxManage setextradata global GUI/MaxGuestResolution any
VBoxManage setextradata "VM name" "CustomVideoMode1" "1280x800x32"

http://chimerhapsody.blogspot.tw/2013/07/virtualbox-virtualbox-customize-screen.html