I am trying to use my Ubuntu on windows Virtualbox. With reference to this page (http://lifehacker.com/how-to-dual-boot-and-virtualize-the-same-partition-on-y-493223329), I managed to boot up Ubuntu as a guest OS on my Virtualbox.
Then I wanted to change the resolution of the screen, so I installed virtualbox-guest-x11 using apt-get install.
sudo apt-get install virtualbox-guest-x11
After this, I tried to restart the machine, but ubuntu would not show it's GUI interface. After I choose Ubuntu on the GRUB bootloader, the screen goes black/purple. At first I thought it did not boot at all, but I was able to log in on command prompt by pressing Ctrl+Alt+F3. It's just the GUI that is not loading.
sudo service lightdm start
start: Job failed to start
I removed the package I installed for the last time, but the problem has not been fixed.
Any help would be appreciated.