Run Virtual Box (or any other gui software) on separate virtual terminal

vt8.sh

#!/bin/bash

# To get the vmid, use:
# VBoxManage list vms

VM="{3b019d6d-16d1-4a8b-909d-8c79e53abd2d}";
XN=4;
XS=/tmp/.X11-unix;

# Create a new X server on vt8
if [ ! -S ${XS}/X${XN} ]; then
  X -quiet -nolisten tcp -noreset :${XN} vt8 &
fi
echo -en "Waiting for X server: "
while [ ! -S ${XS}/X${XN} ]; do
  echo -en '.';
  sleep 1;
done
echo ' done!';

export DISPLAY=:${XN}
/usr/lib/virtualbox/VirtualBoxVM --fullscreen --startvm "${VM}"

echo -en "Stopping X server: "
while [ -S ${XS}/X${XN} ]; do
  kill $(ps aux | grep "Xorg.*vt8$" | awk {'print$2'}) >/dev/null 2>&1
  echo -en '.';
  sleep 1;
done