The Question:

After installing Windows 8.1 on a Mac using BootCamp, an 8GB partition called OSXRESERVED is left behind. How would one safely remove it and reclaim the space for the OS X partition without reinstalling OS X or Windows?

Helpful Background Info:

  • The hardware is a 13 inch MacBook Programming, retina, early 2015, 256GB SSD, running OS X El Capitan (10.11.2).
  • There were no other partitions to begin with. Just Macintosh HD, the Recovery HD, and the EFI partition.
  • Using the BootCamp utility, the hard drive was partitioned with 64GB for Windows and the rest for OS X. An iso of Windows 8.1 was on a USB drive and selected with the BootCamp utility for the install. All instructions were followed, and the Apple drivers were installed (and I checked for updates), all without any issues.
  • After completing the installation, I upgraded to Windows 10 using the downloader on the Microsoft site before booting into OS X again.

My Situation:

I have already removed the OSXRESERVED partition using the BootCamp utility, which also removed the Windows partition. Everything Windows therefore had to be reinstalled, which is very annoying, hence this question. This is the second time it has happened too, but it does not happen every time I set up BootCamp. Presumably the BootCamp utility is supposed to delete it when its done.

Searching around the web, I've noticed that CoreStorage causes a lot of issues for SSD's and Fusion drives with BootCamp. However the reserved partition has been deleted successfully after, just now, reinstalling Windows using Boot Camp again. CoreStorage was enabled on Machintosh HD. All is good.

Disk Utility did not Work:

Last time it happened, I used disk utility to simply delete the partition. Afterwards, it would not let me expand the OS X drive to occupy the free space and made the Windows partition un-bootable (blue screen + sad face). I think the OS X Disk Utility configures the MBR incorrectly in these circumstances, amongst other things. In addition, the BootCamp utility tried to tell me I had too many partitions to remove Windows. Que full system reinstall! I will not do that again.


Boot into OSX, run disk utility. Remove the partition.


In my case i had to reverse the process i.e remove the partition for Windows 10 restart my computer and reinstall windows again. If you tried to format the partition with mac or windows you ran into a trouble which is that mac doesnt accept windows as part of boot camp and sees it as another partition and in order to use boot camp, mac strictly requires you to have your SSD/HDD partitioned as one single partition. That is being said that if you didn't install the Boot camp support you might wanna redo everything. If you have however, you shouldn't worry much about it. As this partition is supposed to disappear and you lose the memory allocation for it anyways.

  • I've read on a few different forums that removing the OSXRESERVED like the question states will cause bootcamp unable to boot. – NetworkKingPin Feb 26 '16 at 6:33
  • Thanks for your interest guys... Bootcamp needs the OSXRESERVED partition to store temporary files as part of the installation of windows. My understanding is that when the BootCamp utility has let Windows install successfully, it will remove that partition by itself because it does not need it anymore. My issue is that it (the OSXRESERVED) partition is not being removed automatically in some cases; hence the question on how to remove it without redoing the whole thing. – puqeko Feb 27 '16 at 6:23

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