When I installed my Macbook Pro, I had a 1Tb drive. When I formatted and partitioned the drive, I assigned 800Gb for OSX and left 200Gb free. I intended the free 200Gb to hold a Windows installation at a later date.

Well, the later date has come, and Boot Camp Assistant wants to partition my drive with 780Gb for OSX and 20Gb for Windows. Clearly it's planning to resize my logical OSX partition down and create a new partition for Windows 7.

Is there some way to get Boot Camp Assistant to instead use the free space on the drive I reserved for this purpose? Perhaps use Disk Utility to format that free space for Windows 7 before running Boot Camp Assistant? If so, what sort of file system should I create?

Some more details: from running diskutil, I see that my disk0 is a 1TB drive partitioned into a 200MB EFI partition, an 800GB LVM partition, a 650MB recovery partition, and 200GB of unused space. The 800GB LVM partition is a physical volume containing a single 800GB logical volume mounted as disk1. Clearly, Boot Camp Assistant is trying to repartition this LVM physical volume rather than the actual disk0.

1 Answer 1


More people have problems with BootCamp trying to partition manually than any other way. This is what I would do:

  1. Boot into recovery mode.
  2. Get into disk utility
  3. Delete the partition you created for Windows
  4. Expand your Mac partition all the way into the available space
  5. Now (assuming you already have the BootCamp media created) Run the BootCamp.app and follow the prompts
  6. Part of the process will present you with a graphical representation of your disk and allow you to set as much space as you want for both the Mac and Windows partition.

The thing you have to learn (or un-learn as the case may be) coming from Linux or Windows is that the first thing you should do is nothing. Let the App and/or Operating System do it's thing the way it wants to. Which means things like, "just plug it in," "follow the prompts in the app," or as a last resort read the (usually brief) instructions in the app or on Apple's support web site.

I've been supporting Macs and PCs for 20+ years and it is a whole different mindset. Yes you can tinker, it's just a different method. What you did is not wrong, it just adds unnecessary complications making it necessary to then work around Apple's work-around that they build into BootCamp so you would not have to do all the partitioning manually.

  • I tried resizing the Mac partition using Disk Utility, but it wouldn't allow me. I hadn't thought to do it in Recovery mode though. I will try that next. Jun 8, 2015 at 20:17
  • If you mean trying to modify the current active partition you are booted from, that will not work and you will, indeed, have to boot into recovery mode. It's the same reason repair disk is not available in Disk Utility booted into the O/S. Jun 9, 2015 at 18:41

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