Migrating Bootcamp to External SSD

I have a MacBook Pro 15 (2018), I am trying to migrate my Bootcamp volume to an external SanDisk Extreme PRO 512GB SSD. I can create a backup image from volume, and then restore image. This works fine, but when I try to boot by holding down the option key, it boots and then get the INACCESSIBLE_BOOT_DEVICE. I have tried all the suggestions on this forum but nothing works.

I am running Catalina 10.15.1

Any help would be appreciated

same here, when I try to inject the drivers I only get “oem21.inf” installed, no other lines.

That usually means the drivers are already there. The issue is as bit different from the inaccessible boot device from a built in drive, since we know what driver needs to get injected. I would see if you can see what driver is missing. When booted from the USB flash drive, try looking in X:\Windows\panther for the setup log, and look in there (using “more”) to see what error messages give an indication on what device is missing a driver.

Sorry I can’t be more specific, but you have entered the secret realm of Windows device drivers.


It’s working now.

I installed Catalina 10.15.2, but also updated the Bootcamp Windows to version to 1909.

I then followed the same procedure, as below

  1. Create Image from Volume.
  2. Format my SanDisk Extreme PRO 500 GB with Disk Utility with ExFAT, and GUID Partition Map.
  3. Restore Image to ExFAT Partition, made. sure it completes.
  4. Booted into Bootcamp holding down the option key and selecting the EFI Partition. Windows then takes ages on “Getting devices ready 63%”, just be patient and let it finish. Make sure nothing else is connected to the Macbook at the time.
  5. Shutdown and rebooted into the Macbook, and imported the new Bootcamp volume into VMWare Fusion, I got an error saying it failed to import. I then shutdown my Macbook and used Command R until the Apple Boot logo, once booted into the Recovery Environment, selected Utilites -> Terminal. In Terminal run csrutil disable to disable System Integrity Protection.
  6. Boot into the Macbook, run VMWare Fusion and import your new Bootcamp volume. It should work now.
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Have a look at 2015 MacBook Pro SSD Upgrade - Runing BootCamp and Windows 10 - IT WORKS - See Last Post! … note the last post.

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The dream of all of us, an external device with working bootcamp on it.
Apple never supported external bootcamp solution, except one:
If you use a native Thunderbolt device, it will work.
Thunderbolt devices are seen like internal PCIe connected devices,
USB-C connected devices with USB-protocol will not work, never did.

Are you saying that my problem is because I’m trying to boot my bootcamp win 10 partition from external ssd?
It’s true?

We have a list of drives that we have tested with and work fine:

he following Mac models were tested with the procedure:

  • MacBook Pro (2018)
  • MacBook Air (13-inch, Mid 2011), 10.13.5, MacBook Air 4,2
  • Mac Mini (Mid 2014)
  • iMac (27-inch, Late 2012), 10.14, iMac 13,2
  • Mac Mini (Mid 2011), 10.13.4, Mac Mini 5,1 (legacy)
  • MacBook (12-inch, Early 2015)
  • MacBook Air (13-inch, Mid 2011), 10.13.5 (legacy)
  • iMac (Retina 5k, 27”, Late 2015), 10.13.6, iMac 17,1

The following external USB-C hard drives where used:

Both external SSD were connected via a USB-C to USB-C cable, or USB-C to USB-A depending on ports available on the Mac.