Installing Guest Additions for Linux

1. Open VirtualBox, and start your UbuntuVB virtual machine. After logging into Ubuntu with your user account, open a terminal window, and type sudo apt-get install dkms, followed by Enter. Then follow the instructions on screen to install the DKMS package. Once installed, close the terminal window.
2. Select Devices | Install Guest Additions from the VirtualBox menu:

3. VirtualBox will mount the Guest Additions ISO file on your virtual machine's CD/DVD-ROM drive, and theVBOXADDITIONS icon will appear on your desktop.
4. Now open a terminal window, and type cd /media/cdrom followed by Enter to change to the CD-ROM directory containing the Guest Additions. Then type sudo sh ./VBoxLinuxAdditions-x86.run, and pressEnter to start installing the VirtualBox Guest Additions on your virtual machine. When finished, the setup program will ask you to restart your Ubuntu VM.
   
   If you're running a 64-bit Linux guest, replace VBoxLinuxAdditions-x86.run with VBoxLinuxAdditions-amd64.run.
5. Close the terminal window, restart your virtual machine, and wait for Ubuntu to boot up. Once is has finished booting up, a VirtualBox - Information dialog will appear to tell you that your guest operating system now supports mouse pointer integration.
6. Enable the Do not show this message again, and click on the OK button to continue. Now you'll be able to move your mouse freely between your virtual machine's area and your host machine's area! You'll also be able to resize your virtual machine's screen, and it will adjust automatically!