I have a MacBook Pro with OS X 10.10 and a Windows 7 Boot Camp install.

I just bought a 64 GB flash drive that I would like to put a bootable copy of Windows on, to reestablish the hard drive as OS X only, and figured it would be easiest to just clone the BOOTCAMP partition that I already have.

I formatted the USB to GUID/NTFS and used dd to clone it:

dd if=/dev/rdisk0s3 of=/dev/rdisk2s2 bs=512 conv=noerror,sync

After 12 hours it finished, and does not work. Windows displays the partition as "RAW"

Anyone have any tips?

2 Answers 2


You cannot boot windows off a USB flash drive. You need a special type of flash drive then windows ultimate which comes with a USB bootable creation tool and a specialized USBkey. There are other methods with which to install USB bootable windows onto and I have tried them and they do not work.


You can try to copy the EFI partition. The EFI partition is required for macOS and Windows to start. That would be rdisk0s1 to rdisk2s1 in your case. You can mount both partition and copy boot files over.

For example:

diskutil mount disk0s1
diskutil mount disk2s1
cp -a /volumes/EFI/EFI/Microsoft /volumes/EFI\ 1/EFI/


dd if=/dev/rdisk0s1 of=/dev/rdisk2s1
  • 1
    It‘s an old question, but some more detailed instructions on how to do that might be helpful nevertheless
    – nohillside
    Jun 20, 2020 at 13:19
  • Unfortunately, I don't have Bootcamp installed and thus I don't know which files are needed.
    – Joy Jin
    Jun 23, 2020 at 5:53
  • 1
    Without Bootcamp how did you verify that your solution works?
    – nohillside
    Jun 23, 2020 at 6:22
  • Well, I used to have Bootcamp that was erased accidentally. However, I still have the option to boot into Windows (which gives me an error) when I press option on boot. I later accidentally erased the EFI partition and restored it using Disk Utility, and afterward that option to boot into windows is gone. Thus I can verify that the EFI partition files is indeed responsible for booting Windows up.
    – Joy Jin
    Jun 24, 2020 at 12:38

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