So I'm running macOS 10.14.5 on a 2012 Macbook Pro. I just put an SSD into the system to replace the internal spinning drive and reinstalled a new copy of the OS from scratch then did the migration assistant using the old drive to copy new data over.

I'm trying to use Boot Camp Assistant to install Windows 10, which I had done previously on the spinning drive. I did not, however, save the Windows Support files from my previous installation of Windows 10 and need to redownload them. I try to do this, but every time I do the system says that it cannot save the files to the USB drive (which is an 8Gb drive that is empty and freshly formatted to FAT / MBR). I've reset my SMC and NVRAM (though I'm not sure how that would help) and reformatted the drive a number of times, to no avail.

The system seems incapable of getting the Windows Support Files. Is there an alternative method of downloading the files? The computer seems to download the files (which previously as a DMG stored in /Library/Application Support/BootCamp, but during the download and attempt to write the files to the USB drive, the DMG never appears.

I checked for open files lsof -p [PID of BCA] and it shows that it's writing to a bunch of .data files in the /private/var/... tree. I'm not sure how to unpack these into the actual data and have no idea what format they are in. Is there any kind of alternative way to download the files? I did try to use BCA in safe mode but it wouldn't mound the FAT partition on the USB drive at all, so that was a bust.

  • Just as an update, I found a script on GitHub which downloaded the package from Apple's update server and unpacked a DMG. The files all look right, but I haven't tried them. If it installs and windows works properly after, I will answer my own question and mark it solved. Jun 19, 2019 at 0:30
  • Your comment has the same link given in Timothy Suttons's answer posted over 3 years ago. I have confirmed that Chris F Carroll's answer does still work. Jun 19, 2019 at 6:44
  • Thank you, I didn't get the link from here so I had no idea. :) Jun 20, 2019 at 4:56


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