using ubuntu-server in full screen mode - VirtualBox

VirtualBox Guest Additions are works for graphical interface, not for text interface...

If you set console frame buffer in grub conf you might have full screen virtual ubuntu server. Take a look at this link for more information..

IMO connecting with ssh to virtual machine is safer than changing frame buffer settings in grub. You can change ssh window height & width as you wish. And nothing is different with real terminal.

You can have the ubuntu server console in VirtualBox start at a resolution that your graphic card supports via the virtualbox environment.

Quick Steps (Source)

• Check the resolutions your graphic card supports via the VirtualBox Environment (VBE).You should be able to find that out by issuing the command 'vbeinfo' in the GRUB console (hit the C key when the GRUB boot menu shows up).

• Pick one resolution, then open '/etc/default/grub' (e.g. sudo vim /etc/default/grub) and change the line #GRUB_GFXMODE=640x480 to something like this GRUB_GFXMODE=1152x864 (where 1152x864 should be your custom resolution which is also supported by your graphic card).

• Now run these two commands one-by-one:

  sudo update-grub
  sudo reboot
  

You should now see your VM's console in the custom resolution that you just set.

(PS: As Javier Rivera said, full screen resolution may not be possible.)

I might try the sudo apt-get install xrdp

and

Next, go to Start –> All Programs –> Accessories –> Remote Desktop Connection from your Windows computer and type the IP address or Hostname of the Ubuntu machine then click ‘Connect’

And, use your Ubuntu username and password.

Or, install kde-desktop package on ubuntu server

on VirtualBox menu - "Devices > Enable remote desktop display"