http://xenserver.org/blog/entry/increasing-ubuntu-s-resolution.html
- install package
sudo apt-get install xvfb xfonts-100dpi xfonts-75dpi xfstt – See more at: http://xenserver.org/blog/entry/increasing-ubuntu-s-resolution.html#sthash.K2SYKXcw.dpuf
2. modify /etc/default/grub
sudo vi /etc/default/grub
GRUB_GFXMODE=1280×960,1280×800,1280×720,1152×768,1152×700,1024×768,800×600
GRUB_PAYLOAD_LINUX=keep
3. apply changes
sudo update-grub
sudo reboot