Ultimately, I'd like to have a USB flash drive with multiple partitions: two bootable partitions for the Windows 7 install disk and OS X recovery disk and a third data partition for storing assorted utilities. I won't bore you with the details of all my various failed attempts to create this drive, except for the most recent one.

I started by using the Boot Camp Assistant to create the bootable Windows installation disk on the USB drive. I was then going to resize that installer partion partition and create the additional partitions for the OS X recovery disk and data partition. Since the Boot Camp Assistant formats the USB drive using the MBR partition scheme I was unable to resize the partition in Disk Utility (at least I think that's why). Trying to be clever, I dumped out the partition table using the -d option in fdisk, changed the size of the first partition (after making a backup of the dumped table) and then read the table back in using the -r option in fdisk. Something about this process rendered the USB drive no longer bootable. Even after restoring the backup table (also using fdisk -r) the drive was still not bootable. How/why did modifying the partition table break the drive's bootabilitiness?

There is obviously much that I don't understand about partitions and booting, so any other tips or resources for creating this fancy USB drive are certainly welcome. Since I'd like to understand how this works at a low level, I'd like to avoid dealing with any 3rd party utilities that magically do everything for me (I was initially hoping to not even have to use the Boot Camp Utility).

1 Answer 1


Usually the first partition in a Windows drive is the MBR partition. Essentially you resized the MBR partition and not the actual Windows partition. Check again with fdisk, there should be 2 partitions. The 2nd one is the one you want to resize. Don't resize the first one.

  • It's actually the USB flash drive that contains the Windows installer that I was modifying, not the hard drive. I edited my original post to try to make this more clear.
    – Pak
    Jan 27, 2013 at 2:48

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