How to Increase the Size of VirtualBox on Mac OS X

Virtual machines have moved out of server rooms and into desktop setups.
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Oracle's VirtualBox hypervisor runs as an application on your OS X devices, allowing you to can run a virtual machine inside the application. You can specify how much disk space to give to that virtual machine, and load another operating system on it. There are two post-installation configuration issues you might run into: getting VirtualBox to play nicely with modern screen resolutions -- especially with Retina Display devices -- and increasing the amount of disk space allocated to a given VirtualBox instance on your computer.

1 Adjusting Screen Resolution

2 Search for

Search for "," one of the configuration files for VirtualBox. It resides in your VirtualBox folders, but depending on the version of VirtualBox you have installed, it may be in the Extra or SystemConfiguration subfolder.

3 Make a backup copy of this file

Make a backup copy of this file by copying and pasting it somewhere else.

4 Open the original file with a text editor

Open the original file with a text editor.

5 Search

Search within the file for "Graphics Mode," which should be in XML tags. Underneath the tag containing the element "Graphics Mode" there's a String tag containing the element "1280x1024x32" or something fairly similar. That string contains the pixels and color depths that VirtualBox uses for your display. Change that to whatever resolution your OS X machine supports.

6 Save the file

Save the file. Make sure to uncheck the check box that says "save with a .txt extension" to save it with the .plist file extension.

7 Start VirtualBox

Start VirtualBox; it now uses the new screen resolution.

8 Resizing the VirtualBox Disk

9 Back up your existing virtual drive

Back up your existing virtual drive, or VDI, file by starting the VBoxManage utility in VirtualBox, and then entering the following command at the command prompt:

10 Clonehd

clonehd <path to your original vdi file> <path of the copy>

11 Take a few minutes

This may take a few minutes to complete.

12 Resize the virtual box drive

Resize the virtual box drive by typing the following command into VBoxManage:

modifyhd <path to your vdi> --resize <new size in megabytes>

Note that the "resize" flag has two hyphens preceding it. Remember that there are 1024MB in a gigabyte.

Shut down and restart VirtualBox to access the additional disk space.

  • Use your guest operating system's disk management tools to extend the partition it sees to cover the enlarged VDI file. For Windows, search for "Computer Management," and then right-click on the partition corresponding to your VDI file and click the "Extend Volume" button so that the guest operating system formats the remaining unallocated disk space.

Ken Burnside has been writing freelance since 1990, contributing to publications as diverse as "Pyramid" and "Training & Simulations Journal." A Microsoft MVP in Excel, he holds a Bachelor of Arts in English from the University of Alaska. He won the Origins Award for Attack Vector: Tactical, a board game about space combat.