Is there a way to setup an external Bootcamp drive as the default startup disk? I want to do this in order to enable hyper-v virtualization on Windows on a MacBook Air (Early 2015 running 10.12.3 Sierra).

This is the error that I'm getting:


Windows 10 is installed on an external SSD in a 2.5" enclosure that uses USB 3.0. I already installed the Windows Support Software from Bootcamp onto it.

I can boot up from the external SSD by holding the Option key during boot, but virtualization is disabled.

Unfortunately Apple Care reps also couldn't find a solution.

  • We made sure that the drive was functional by running First Aid
  • The external drive uses a GUID Partition Map
  • 1
    I understand the question, but was just wondering whether you'd still want to be able to do this if virtualization was enabled? In other words, I guess what I'm wondering is if you're asking the right question? Have you read all the answers and comments here to see if there's anything useful to you? For example, there's a comment by Chui Tey on 23 Dec 2016 that I found interesting. Either way, maybe something there will solve your main issue. – Monomeeth Mar 20 '17 at 0:04
  • How did you managed to install Windows in an external drive? right now Im trying different approaches and I can't get it to boot – PERR0_HUNTER Mar 21 '17 at 7:16

There are a few things you can try to resolve the exact issue in your question.


Older Macs had what's called Parameter RAM (PRAM), newer Macs use Non-Volatile Random-Access Memory (NVRAM). It may be worth you resetting this. Here’s how to:

  1. Shut down your machine. Yes, a full shut down, not just logging out.
  2. Press the power button and then press the commandoptionpr keys. You have to make sure you press these keys before the gray screen appears or it won’t work.
  3. Hold those keys down until your Mac reboots again and you here the startup chime.
  4. Let go of the keys and let your Mac reboot normally.

Note: When you log back in you may need to readjust some of your system preferences (e.g. speaker volume, screen resolution, startup disk selection, time zone information, etc).

Once you boot in, go to System Preferences > Startup Disk and check to see if you can now select your Windows Bootcamp volume as your startup disk. If you still can't, try the step below.

Use the SDM to change your default Startup Disk

Another way you can select your default startup disk is to use the Startup Disk Manager. Follow these steps:

  1. Shut down your Mac
  2. Switch it on again and immediately press and hold the option key
  3. Release the key when your bootable volumes start appearing
  4. Press and hold the control key while you select your Windows Bootcamp volume

Once you've done this, your Windows Bootcamp volume should be the default startup disk. If you still can't, try the step below.

Use the Windows Boot Camp Control Panel

You can also try using the Windows Boot Camp Control Panel instead. Use these steps:

  1. Boot into Windows
  2. View the Control Panel
  3. Select the Boot Camp Control Panel
  4. Select the Startup Disk tab
  5. Select the Windows volume as your default startup disk

Once you've done this, your Windows Bootcamp volume should be the default startup disk. If you still can't, see other options below.

Other options

Another couple of options are:

  • Trying rEFInd
  • Using Terminal to set your Startup Disk (if you're comfortable doing so)

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