This will mount a CD image in your Ubuntu virtual machine with the Guest Additions installer; you should see the icon appear on your virtual machine’s Desktop. Double-click on the icon to mount it.
Next, open a Terminal window.You’ll need to navigate to the /media directory, and then change to the directory representing the CD image.
The name is usually something like VBOXADDITIONS_version_release, for example:
Change to the VBOXADDITIONS directory, and then launch the installer. You can do this with this command for a 32 bit virtual machine:
For a 64 bit machine:
Type your password to authenticate, and the Guest Additions Installer will launch. It usually takes a few minutes to complete, and once you’re finished, the installer will return you to the Terminal prompt.
Once the installer is done, reboot your Ubuntu virtual machine.
When your Ubuntu virtual machine reboots, it will now support mouse integration, and you’ll be able to increase the resolution beyond 800×600.
The video below will show you how to install Guest Additions with Ubuntu 10.04. Once you see how it’s done it will only take a few minutes and one VirtualBox restart, then you’re good to go.