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I am going to be setting up a new (to me) Mac Pro 4,1 with multiple internal hard drives. I want to run Yosemite most of the time with Windows 7 virtualized in a window for a few programs I need to run that require Windows.

Occasionally, though, I would like to boot directly into Windows at startup for maximum performance (for games).

Is it possible for VirtualBox and Boot Camp to share the same Windows installation? In other words, can I dedicate one hard drive, or one partition, to Windows 7, and then either

  • choose to boot from that drive (or partition) at startup, or
  • boot into OS X, run VirtualBox, and have Windows inside the virtual machine boot from the same Boot Camp drive (or partition)?

My goal is not only to save disk space (by installing Windows and the software I need to run under it in just one place, rather than on one real drive and one virtual drive) but also to avoid having to buy multiple Windows licenses.

  • Parallels can do it, Boot Camp & VM from one installation - not that that's an answer to your question... – Tetsujin May 18 '15 at 17:25
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The answer is No. Sorry. I have done this already. Here is the problem. VirtualBox and your Apple use different hardware. If you try to switch between the hardware you are going to drive windows insane.

If you first install Windows using VirtualBox's virtual hardware and a physical disk partition, then switch to Apple's physical hardware with the same physical disk partition then you have to run Microsoft's "System Preparation Tool". This tool is meant to be run once, not repeatedly. See the procedure at this link

The other problem would be now are you going to activate the software for both machines. Are you going to active while running under VirtualBox or BootCamp?

When you boot between the physical Apple hardware and the virtual VirtualBox hardware, the Windows operating system is going to detect the change. For example, the two machines do not share the same MBR. Each MBR will have a different signature. Windows stores this signature in its boot partition and compares the value with the MBR when booting.

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While VirtualBox is capable of Raw Disk Access it is not designed to use the Windows Boot Camp partition as a virtual machine. In other words it does not handle the Windows Product Activation between running it physically and virtually. VMware Fusion, a paid product, is capable of seamlessly handing using the Windows Boot Camp partition as a virtual machine.

  • Sounds from Tetsujin's comment above that Parallels can do this as well. Can you clarify how Fusion gets around the issues with the virtualized hardware and the real hardware being different that David Anderson explains in his answer? – dodgethesteamroller May 18 '15 at 18:32
  • @dodgethesteamroller, Yes, Parallels Desktop for Mac can do it also however I prefer VMware Fusion and why I mentioned it over Parallels. As to how VMware Fusion manages product activation using VMware Tools it manages two distinctive activation database and swaps them out depending on whether or not it being booted in the virtual environment or the physical environment. This of course requires being activated in each mode but once done then going forwards it's seamless. – user3439894 May 18 '15 at 18:44
  • @dodgethesteamroller, BTW what David Anderson mention is an very incomplete portrayal of how the process takes place, the MBR signature is but one of many items used to create the hash stored in the database, a disk file on the OSes filesystem, that is queried to see that all is as it should be. – user3439894 May 18 '15 at 18:44
  • You mention "being activated in each mode"--does this mean even with Fusion using only the Boot Camp partition, no separate virtual machine install, I would need to buy two Windows licenses? – dodgethesteamroller May 20 '15 at 3:46
  • dodgethesteamroller, No, only one Windows license is required to install it on the Boot Camp partition and to use the Boot Camp partition install as a virtual machine. – user3439894 May 20 '15 at 3:53

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