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How to Use Boot Camp on an External Drive to Run Windows on a Mac

Boot Camp Assistant Icon

Boot Camp and Boot Camp Assistant allow you to install Windows on your Mac. It’s a nice capability that lets you select – at boot time – which operating system you wish to use: macOS or Windows.

One of the downsides to Boot Camp and the Windows installer is that it restricts you to only installing Windows on your Mac’s internal drive. While Boot Camp Assistant can partition your startup drive for you to make room for Windows, there are bound to be many of you who just don’t have room to spare on your startup drive to install Windows.

Installing Windows on an external drive would be a great solution to the problem of available space, but as we said, Boot Camp and Windows impose a restriction on installing to an external drive.

Or do they?

There are actually a few ways you can successfully install Windows on an external drive. They range from creating clones of an existing PC installation or using Microsoft IT tools for installing Windows. But the method we’re going to outline here is a bit different. It allows you to install Windows on an external drive without first having Windows installed on a PC or in a virtual environment.

This is an advanced process with quite a few pitfalls that can trip you up. Be sure to read through the process before undertaking it. Also, make sure you have a current backup before beginning.

What You Need to Install Boot Camp on an External Drive

  • 4 GB or larger USB flash drive.
  • Bootable external drive. We’re using a USB 3.0 drive, but a Thunderbolt drive should work as well.
  • Boot Camp Windows Support Software.
  • VirtualBox virtualization app (available for free).
  • A licensed copy of Windows 10 ISO or an install DVD.
  • Wired keyboard and mouse. During the Windows installation, the drivers for Apple wireless keyboards and mice aren’t installed until the very end of the process. If you’re not using a portable Mac with a built-in keyboard and trackpad, you’ll need a wired keyboard and mouse to complete the installation.

Prepare the External Drive for Installing Windows

The external drive that you’ll install Windows on needs to be prepared by erasing and formatting the drive for use with Windows.

Warning: The erase, format, and partitioning process will delete all data currently contained on the external drive.

  1. Ensure the external drive is connected to your Mac.
  2. Launch Disk Utility, located at /Applications/Utilities.
  3. In the Disk Utility sidebar, select the external drive that will be used for Windows. The device will likely have the name of the external enclosure’s manufacturer listed. Do not select the volume located just underneath the device name.
  4. Click the Erase button in the Disk Utility toolbar.
  5. Use the dropdown menu to set the Scheme to “Master Boot Record.”
  6. Use the dropdown menu to set the Format to “MS-DOS (FAT).”
  7. You can use any name you wish (up to 8 characters), but we suggest naming the external WIN10.
  8. Click the Erase button.

The external drive will be formatted and a single MS-DOS (FAT) volume will be created.

Prepare the USB Flash Drive for the Windows Support Software

The USB flash drive needs to be formatted to accept the Windows software that Boot Camp Assistant will download and install.

Screenshot of flash drive formatting window
The flash drive needs to be formatted for use on Windows

Warning: The process of preparing the USB flash drive will delete any data contained on the flash drive.

  1. Make sure the USB flash drive is connected to your Mac.
  2. Launch Disk Utility, located at /Applications/Utilities.
  3. In the Disk Utility sidebar, select the USB flash drive device. The device will likely have the name of the USB flash drive manufacturer listed. Do not select the volume located just underneath the device name.
  4. Click the Erase button in the Disk Utility toolbar.
  5. Use the dropdown menu to set the Scheme to “Master Boot Record.”
  6. Use the dropdown menu to set the Format to “MS-DOS (FAT).”
  7. You can leave the Name field as is.
  8. Click the Erase button.

The USB flash drive will be formatted and a single MS-DOS (FAT) volume will be created.

Download Boot Camp Windows Drivers

We only need Boot Camp Assistant for its ability to download all of the Windows drivers we’ll need to ensure the install of Windows will run correctly on Mac hardware. We won’t be using Boot Camp Assistant to partition a drive or step us through the install process.

Screenshot of boot camp assistant
The latest version of the Apple drivers that Boot Camp needs can be downloaded using Boot Camp Assistant.
  1. Launch Boot Camp Assistant, located at /Applications/Utilities.
  2. In the Boot Camp Assistant window that opens, click the Continue button.
  3. In the Select Tasks window, remove checkmarks from “Create a Windows 7 or later version install disk” and “Install Windows 7 or later version.” Ensure the checkbox labeled “Download the latest Windows support software from Apple” is checked, and then click Continue.
  4. Select the device you wish to have the Windows support files installed on; this should be the USB flash drive you prepared earlier. After making your selection, click Continue.
  5. Boot Camp Assistant will download and install the needed Windows support software on the selected device.
  6. Once the install is nearly complete, you’ll be asked to provide your administrator password so the Boot Camp Assistant can change the file permissions on the USB flash drive. Provide your administrator password, and click Continue.

The Windows support software has been installed on the USB flash drive.

Use VirtualBox to Install Windows on the External Drive

This is the tricky part of the process, at least in the sense that we’re going to trick Boot Camp and the Windows installer into thinking your external drive is actually your main internal drive, or in the parlance of Windows, your C: drive.

You could perform this tricky bit of virtualization using Parallels or VMware Fusion, but we’re going to use VirtualBox because it’s free. You can download the app from the VirtualBox website.

Once you download and install VirtualBox, we’re ready to begin the installation process.

Most of the virtualization trickery will be performed from within Terminal, so go ahead and launch Terminal, located at /Applications/Utilities.

Screenshot of diskutl command
You can find the external drive by looking for the name, type, or if this is your only external, by the location [external, physical]
  1. With the external drive you formatted for installing Windows on connected to your Mac, enter the following Terminal command without the quotation marks: “diskutil list” and then press enter or return.
  2. A list of all attached disks will be displayed in Terminal. Scroll through the list and locate the external drive you plan on using to install Windows. If you followed our suggestion earlier, it will be named WIN10 and be of the type DOS_FAT_32.
  3. Once you locate the external drive, make a note of its Identifier. The Identifier appears in the last column and will have the format of the word “disk” followed by a number. In our case, the identifier is disk4.
  4. Now that we know the disk identifier, we need to eject the disk so it’s no longer connected logically to the Mac (it will still be connected physically).
  5. Locate the WIN10 disk on your Desktop or in the Finder window sidebar.
  6. Right-click on the WIN10 disk and select Eject from the popup menu.

Use VirtualBox to Map the External Drive to a VirtualBox Disk

The next step in the process is to map the external drive to a VirtualBox disk.

  1. In Terminal, enter the following without the quotation marks: “sudo VBoxManage internalcommands createrawvmdk -filename “bootcamp.vmdk” -rawdisk /dev/disk4″
    Note: Be sure to replace /dev/disk4 with the actual disk number you found from the disk identifier, and then press enter or return.
  2. At the Terminal prompt, enter your administrator password, and then press enter or return.

The bootcamp.vmdk virtual disk will be created in your home folder.

Create a VirtualBox Virtual Machine for Windows

We will use VirtualBox to install Windows 10 to our external drive. We can do this because in the previous step, we mapped the external drive to a VirtualBox virtualized disk.

Virtual Box VM
The Windows VM you create uses a virtualized connection to your external drive.

In order for VirtualBox to be able to access the external drive, we need to launch VirtualBox with elevated permissions. Once again, we turn to Terminal.

  1. Enter the following at the Terminal prompt without the quotation marks: “sudo /Applications/VirtualBox.app/Contents/MacOS/VirtualBox” Press enter or return.
  2. If asked, supply your administrator password, and then press enter or return.
  3. VirtualBox will open.
  4. In the VirtualBox window, click on the New button in the toolbar.
  5. In the sheet that drops down, enter a Name for the installation; we suggest WIN10.
  6. Set the Type to Microsoft Windows.
  7. Set the Version to Windows 10 (64-bit).
  8. Click the Continue button.
  9. Accept the default memory size, and click Continue.
  10. In the Hard Disk sheet, select Use an existing virtual hard disk file.
  11. Just below the option to use an existing virtual hard disk file is a dropdown menu for selecting a file to use. You may notice the menu is empty or does not contain the virtual disk file we created earlier. Click the folder icon just to the right of the dropdown menu. This will allow you to browse to the bootcamp.vmdk file, which is located in your home folder. Select the bootcamp.vmdk file, click the Open button and then click the Create button.
  12. VirtualBox has created a virtual environment for us to install Windows 10 in that will actually perform the install on the external drive. The next step is to mount the Windows 10 ISO you downloaded earlier from Microsoft.
  13. In VirtualBox, select the Windows 10 virtual machine, and then locate the Optical Drive. This is usually located in the Storage section of the virtual machine. Click the Optical Drive item and select Choose Disk Image.
  14. Browse to where you downloaded the Windows 10 ISO.
  15. Select the Windows 10 ISO, then click open.

Install Windows on Your External Drive Via VirtualBox

  1. Start the installation process by clicking the Start button in the VirtualBox toolbox.
  2. The Windows 10 installation will start. Follow the onscreen instructions until you come to the Windows Setup screen with the heading “Which type of installation do you want?”
  3. Select the “Custom: Install Windows only (advanced)” option.
  4. The Windows setup will display the currently available drives and partitions that Windows can be installed on. Because the external hard drive has been assigned to the VirtualBox machine, it is the only drive that will be listed.
  5. When we used Disk Utility to format the drive, we chose MS-DOS (FAT), which is incompatible with Windows 10. We did this because Disk Utility can’t format with NTSF, but the Windows installer would recognize MS-DOS. All we need to do now is change the drive’s format to NTSF.
  6. Select the drive, and then click the Format button.
  7. Wait until the format is complete (the Next button will become available), and then click Next.
  8. The Windows installation will start, with files being copied to the external drive.
  9. Warning: An extremely important step follows…
    When you see the message “Windows needs to restart” immediately shut down the virtual machine by clicking on the red close button on the window. Select “Power off the machine” from the list of options, and then click OK to power off the virtual machine.
Windows 10 Install
Windows Setup will install the needed files to your external drive. Be sure to prevent Windows Setup from automatically restarting.

At this point, the Windows installer has copied all the files to the external drive, and has set up a boot environment that you can start your Mac from. Next time you boot from the external drive, Windows will complete the installation process.

Restart Your Mac With the External Windows Drive

  1. Close any apps you may have open, then restart your Mac.
  2. Hold down the Option key during the restart. This will cause the Mac’s Startup Manager to display a list of drives you can start from. Use the arrow keys on your keyboard to select the Windows drive.
  3. Your Mac will boot from the external Windows drive. The bootup process can take a while, so be patient.
  4. Windows will finish the install process. At some point during the installation, Windows will restart your Mac. When it does, your Mac will restart with the normal Mac OS. You need to be present to hold down the Option key and select Windows to start from.
  5. Windows will finish the installation and present you with the Windows desktop.

Getting Apple Hardware Working Under Windows

The USB flash drive you used earlier to make the Windows Support software contains all the drivers you need to install in Windows for the Apple hardware to work.

Boot Camp Setup screen
To complete the Windows installation, run the Boot Camp Setup app to install the needed Apple drivers.
  1. Make sure the USB flash drive is connected to your Mac.
  2. Click on the Windows Start button and select File Explorer.
  3. In the File Explorer sidebar, select the USB flash drive, it will probably have a D or E drive letter assigned to it.
  4. Open the Boot Camp folder
  5. Run the Setup app inside the Boot Camp folder.
  6. Follow the on-screen instructions to install the Boot Camp drivers.

Once the installation completes, all your Apple hardware, including wireless keyboards and mice, should be working.

Tom Nelson
the authorTom Nelson
Tom has been an enthusiastic Mac user since the Mac Plus. He’s also been known to dabble in the dark side, otherwise known as Windows, and has a well-deserved reputation for being able to explain almost anything to anybody. Tom’s background includes more than 30 years as an engineer, programmer, network manager, software tester, software reviewer, database designer, and computer network and systems designer. His online experience includes working as a sysop, forum leader, writer, and software library manager.
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  • If folks are having grief with this solution then try the solution at https://9to5mac.com/2017/08/31/how-windows-10-mac-boot-camp-external-drive-video/. It takes about 3 hours but it worked perfectly.

    Some gotchas…

    1) You MUST have a separate wired (or USB wireless) keyboard and mouse, even if using a Macbook. Bluetooth is no good. This is temporarily needed during setup.

    2) The free version of WinToUSB does not support Windows 10 October 2018 release, so download the April 2018 version instead or buy WinToUSB.

    3) The tutorial uses Windows 10 Pro, but I successfully used Windows 10 Home.

      • Sri, if you are performing the above 9to5mac.com solution then yes I believe you can do this… but your complete drive will still be erased. After step 8, this is where you split the main partition in two with a 500GB partition. Then in step 22 this is where you choose the EFI boot partition and the Windows partition. The other partition you create can be used however… at least in theory!

  • Do the Apple bootcamp drivers have to be downloaded to the flash drive every time you start over? What I’m wondering is; Does Apple do more than just place a folder on your USB flash drive? When we use Vbox to install windows to the external drive we are no longer using the Apple BootCamp application. I have been at this for over a week now and have repeated the steps over a dozen times. Well over. But, I don’t repeat this particular step every time since the USB flash drive with Bootcamp support technically doesn’t get used until widows is actually installed and running. I had a similar problem on Macos 9.1 PPC running the BlueLabel Windows emulator and getting it to recognize the Boot Partition. It was the same with the Bochs emulator.Right now I’m running El Capitan 10.11 on a 2007 iMac trying to install Win7 SP164bit on an external hard drive.Just straight Usb adapter cable from the back of iMac to the bare hard drive (WD 40gb made in 2003).I know the USB adapter works on this iMac because it will boot MacOsX 10.5 to 10.11. I have an External Iomega drive box with firewire and USB with a 500gb WD drive and doesn’t seem to work for purposes of this exercise we are doing here either. Along with El Capitan I’m running OSX 10.6 snow lepeord. What am i doing wrong?

    • Heres the the thing, when using Bootcamp as normal, it need a single partitioned disk . Bootcamp itself creates the windows boot partition and installs the needed drivers and draws a map right to the boot partition so when you put in the windows install disk it sees it.Does the Vbox emulator hand it off to Bootcamp, Because the Mac doesn’t see it when it is restarted after Vbox extracts the files to the External disk.Does Bootcamp boot the disk or the Mac Os itself?

      • VBox does not extract the files to the external disk. You do. And they aren’t needed until AFTER you’ve successfully installed. When at the Win 10 desktop you would open the USB explorer and then find and run the exe to extract. Like a “START” program that discs come with. If you can’t get Windows installed, it certainly isn’t because of the USB because VBox doesn’t use the USB. But … Windows may not see the USB you do create, as in my case. You need to format the USB as a MBR “FAT32.” That selection is not available in Disk Utility, only MS DOS FAT is. Macs can read FAT32 though. So you need the USB formatted from a Windows machine first. Either with an existing one you have or waiting until Windows is installed then make that your first step with your new system: format the USB and reboot to Mac. Otherwise Windows might not recognize the USB and will ask if you want to format it. Again, new quirk with formatting in Disk Utility? (My Air is a 2015 Mojave so I don’t know if that means Disk Utility is now different.) When you return to Mac OS side with the formatted USB, Bootcamp will see it when you download the files to it. It is the ONLY thing you do from Bootcamp. A simple download the support files. Bootcamp is not used to install them or do anything else it usually does when using your native iOS drive as target. Think of Bootcamp as just another file explorer tool in this situation. Open Bootcamp, (ignoring the window and what it asks or tells you) and select from the menu at top the action to download the Windows Support Files. Select your Win OS, the USB, and let it run. (Yawn… takes a bit.)

  • I can’t seem to get it running. I agree with some commenters that at least for newer macs it’s essential to have the EFI partition on the external drive so it can be selected as a bootable drive. Whatever I do I can only seem to get that EFI partition if partition the disk with GUID partition table, not with MBR. But then Windows complains about the GPT format of the disk and doesn’t let me install the free space/partition next to the EFI partition on the disk. Using MBR like in the description in the article itself does like in the screenshots above not give me an EFI partition and then Windows also doesn’t install one – that makes the drive just not bootable from a Mac (2017 iMac in my case).

    Any hint on how to get closer? I’ll try some other ways to get external drive Windows going but that one I had liked. Too bad.

    • This is where i’m stuck. I’m trying to install win 7sp1. on a ’07 imac and i think it lacks the drivers a full windows 7 install would have. I think this because when i enable efi in vbox and start it hangs in the windows startup screen 5 or so seconds into the very start of install.Wnen i dont enable efi it installs and no boot on mac. no efi. The only thing i havent tried is letting vbox finish the install instead of shutting it rtght off.It already has a direct line to the drive.

      • Ray and Helmi: I ran into these same two things. They are buried in my lengthy replies below so may have been missed.

        1) No you do not have to reinstall bootcamp files to the USB every time you start over. But … you DO need to format it from the Windows side once that is up and running. As a FAT32. Then switch over to Mac OS and install the bootcamp files, then reboot to Windows and all will be ready to run. So you don’t really have to do it at the start of this process, but can wait until the end when you have a working Windows OS.

        2) I am certain the problem with some drives not creating that EFI during formatting is completely a driver issue. Something in “compatible” drivers is different enough to screw up the formatting with EFI. Even though you can select “EFI” in the VBox settings step, it has to be there first for VBox to work with. Some drives don’t get correct formatting with an EFI partition using older drivers or the generic ones. Don’t use the iOS’ generic default driver for it! Think about prescriptions: “generic vs Brand name.” Same key active ingredients, but slightly different formulations. Should be the same and for most people they certainly are. But for some people there is a significant difference. Same with drivers. For most uses, or just storing data, those finer differences in drivers don’t mean squat and any of them will still let you use the drive successfully. You never notice what wasn’t done correctly with the drive behind the scenes because you didn’t need it. But … for some systems or uses, the driver has key ramifications, such as in this instructional. It won’t be true for everyone, but as you can see it is for enough of us. Whether it’s a difference between HDD or SSD, or subtle differences in laptop hw or sw releases in combination with certain kinds of drives or USB versions, etc., I don’t know. So go with the Brand driver before starting this process. Go to the manufacturer’s website. Don’t grab all the downloadable software, and don’t download it bundled with other drivers or utilities. Regardless what their site says, you do not need ANYthing else but the driver alone for your HDD/SSD. And all manufacturer’s have it available like that somewhere.

        So … technically preparing your drive should look like this:

        Step 1 – download (but don’t yet install) the most current driver for your external target drive from your drive’s manufacturer. (Mine was Samsung) If a new drive, do not use the one that comes with the empty drive. Ignore them.

        Step 2: Reformat the drive first, GUID like this tutorial says, but it won’t be correct yet. It is to present to the OS a clean slate so to speak when it reformats it later with the correct driver, without anything funky on the drive or any manufacturer specific formatting style.

        Step 3: install the downloaded drivers to your MAC OS.

        Step 4: Then do the formatting step in this tutorial AGAIN. It will now create the EFI this time around because the drivers are now correctly ready. For me having the drive formatted initially to wipe it clean was important before installing the new drivers in the first place. Then with the correct drivers installed, Mac iOS was then able to reformat it the second time with the EFI as it should.

        • I have the exact same problem as Helmi. I have a 2016 MacBook Pro with latest Mojave and I’m using a Samsung T5 SSD as the external drive. The SSD already has the latest firmware installed.

          As mentioned by Helmi I can only get the EFI partition if I format as GUID, but then Windows will not install.

          @JuJu… you mentioned downloading the latest drivers. Are you referring to the drive firmware or the drivers the Mac uses to communicate with the drive? For the Samsung T5 there is only one download and that updates the firmware. Where did you get your driver, please?

          @Juju: In step 2 you say “Reformat the drive first, GUID like this tutorial says,”… but the tutorial nevers ask us to format in GUID! Just to confirm, you formatted your drive with MBR/MS-DOS(FAT) and got both an EFI partition and a DOS_FAT_32 partition?

          Thanks in advance for your help.

          • Hi. I’m sorry I was unable to see this sooner. You are correct, the original instructions above said nothing about the GUID but he replies below in several places correcting everyone to do it as GUID. I know he replied to Jared on August 28 and to Daniel on September 24, and a few other places. I combed every single comment below before doing this process, highlighting key points and making notes on the original instructions so that I’d know when I got to each step. He was right about his replies to comments on the formatting, but because of what I assumed was a driver issue it still didn’t create the EFT autimatically like it should have. Not until I installed the SSD drive’s driver manually to Mac OS before formatting the drive did it work exactly like he said.

            I saw “firmware” updates for the T5 on Samsung’s site too, and I always avoid those like the plague. I was tenacious until I found a link for just the driver alone. It is there, they always are, but are not readily noticeable or easy to find. I’ll go back and check where I found it and reply again with that info.

          • Ok. Found it. I had to do this for a WD drive too, and I was able to get the driver only from WD site. For Samsung T5 however, I downloaded the firmware but did not install. In Mac you can look at application files by showing the package content in Finder, by right clicking on it and selecting show content. So instead of running the Samsung firmware setup, I showed the contents for samsungportableSSD_Setup_Mac.pkg, (or SamsungPortableSSD.app – my notes reference both because one came inside a folder on the new SSD and the other I downloaded from their site.) Then I navigated to /contents/resources/samsungportableSSDDriver1.6.0.pkg. That’s the actual package I ran, not the setup. I only wanted the driver, and I hate being bamboozled into installing bloatware that the manufacturers wrongly assume will be helpful for me. So by digging into app files you can find the driver specific file. Again, WD is more humane and offer just the driver to download on their website in addition to their bloatware.

          • To finish answering your questions, and clarify the confusion of MS-DOS vs FAT32 – they are for two different things:
            1) The MS-DOS formatting is for the external drive for the Windows OS, not the USB for Bootcamp support files. I formatted the external drive I was installing Win10 on as GUID / MS-DOS initially, just to rid it of all contaminants (preinstalled software and formatting.) Then … I installed the Samsung driver 1.6.0 to the Mac OS manually. Then … I reformatted the external SSD a second time, GUID / MS-DOS. The second time the EFI was successfully created. But not the first. That’s why I think it’s a driver issue. It remains MS-DOS only until the start of the Windows install. There it sees the EFI, and you select the MS-DOS partition for the OS and Windows automatically reformats it as an NTFS. So MS-DOS isn’t ever really used by Windows. If the drive were NTFS to start out, Mac OS could not work with it to integrate through Vbox etc. Thus, the shell game.

            2) The Fat32 format was only for the USB that holds the Bootcamp support files, and not for your external OS drive. Mac can read MS-DOS and MS-DOS FAT32, but their Disk Utility has no option to format FAT32. It was important though because formatted as MBR/MS-DOS, windows did not recognize it at all and only offered to reformat it whenever I plugged it in. So, I took them up on the offer, erased the Bootcamp files and reformatted it as FAT-32 as Windows defaulted it to, then went back into Mac OS and ran the Bootcamp download again pointing to the USB drive now FAT32. Windows then recognized it when I returned and all Bootcamp drivers were successfully installed.

        • Exactly, I see that now.When Bootcamp installs Windows on a partition on your main drive it needs a whole unpartitioned disk because it needs accsess to those tiny boot partitions way up at the front of the disk,that’s where the Extensible Firmware Interface is stored.Seagate doesn’t supply drivers for my cheapy 500 gig storage drive.It’s 2012 model HD, they have probably archived them already. Not done looking yet. The drives manufactured application was surveillance and video storage. Heres the thing though, the mac can write to the boot sectors on it.I have booted from it and wiped my main drive clean on a couple occasions.When I reboot holding down the option key it shows up on the list along with the main drive and the flash drive with my OSX installers on it, 10.11 and 10.6. When I had Win XP on the main drive it showed up. The one thing in common here is the Mac GUID partition scheme. When bootcamp installs Windows it only erases the disk its going to install on , not the whole drive.Leaving the Mac GUID intact.It’s a good thing I didn’t put this 500gig drive in the iMac because I’m guessing the 250Gig one that is in there has the windows drivers on it.

        • Yes ,this was the sames problem I have encountered before with certain manufacturers HD’s and trying to find Mac drivers.It’s been my experience that Macs generally are not to picky about what they will install on and boot from as far as internal or external drives as long as they don’t have conflicting ID’s. 0,1,,2,3 etc. 0 being the optical drive.This is a nifty trick. I like it and I have a WD sata drive on the way and I’ll keep tinkering with it. I know it will work. This also could be an issue with the Win 7 SP164bit ISO I purchased.Although it installs and runs just fine within the Vbox emulation. It may not contain all the necessary drivers.Or,I may be shutting the terminal down too early or too late.Part of the fun of learning.

          • If you had a new drive coming, do what I started to do. The minute I plug it in, I copy ALL the folders/files that came on the drive new. Then I reformat it – cleanse it so to speak, of all previously installed software and specialized formatting. Then I can dig through the files I copied off of it for the actual driver .pkg to install. NOT the firmware or software, etc. Dig until you find only the driver itself. I install that on my Mac, regardless if it thinks it needs it or not. (If the external drive is older but never used before, I would go to manufacturer website first for latest driver if possible, using what came on the drive only if I couldn’t find it online.)

            Also don’t worry about your ISO not having all the drivers it needs. Once Windows is installed and you get to the desktop, your Bootcamp USB will install all drivers you need.

    • Helmi,

      I found the same problem. I have a 2019 iMac (6 core/16GB/256SSD) and used an Samsung T5 SSD via USB and never could get the Mac to see it.

  • The virtualbox was showing a black screen when trying to run with EFI enabled.
    Just in case you are having this issue, I fixed it changing Settings->Display->Graphics Controller to VBoxVGA instead of VBoxSVGA

  • My apologies to all for my typo in all of my replies. My comments keep referring to the “EFI” partition as “EFT.” I think it autocorrected it to EFT each time and I didn’t notice.

    There is NO EFT, it is EFI.

    If the moderator could go into my replies and change those acronyms, it might save confusion for others.

  • My 2018 MacBook Air on Mojave tried installing windows 10 October update and April update and it keeps bringing me to the recovery screen to enter a password saying to unlock the disk. I am able to select the EFI boot and this is what happens. When I enter in my password it just restarts to Mac OS. The external drive is a WD Passport. Followed all the suggestions with enabling efi. Any suggestions? I’ve exhausted almost every option commented.

    • Zack

      I had that happen to me too. Twice. There are two things I had to do:
      1) I had install the drivers (not the software) for the actual external SSD/HDD fresh on the Mac OSX side. Run the driver installer manually, downloaded fresh from the manufacturer’s website. I explain this below, and, 2) Get over myself and my frustration/drama about starting all over from scratch. It’s not the headache groaner I thought it would be. Each time gets easier and I went from it taking two days for just my first attempt to get me to where you are, to my fourth fresh restart taking only 40 minutes start to finish, sitting on the Windows desktop all set up and perfect. So don’t disregard starting over. You’d be amazed how many errors or issues you suddenly don’t experience again the next time you give it a try, for whatever wonky reason. It’s a time saver! I’m living proof. You’re a veteran now, once you made it through the instructions once.

      As for the why it happens, and how to do things:

      The results and wrinkles of the install can be random because the series of steps we go through working with the innards of a virtual software, a virtual machine, AND the Mac OS, add in the code for a new OS on the VM, and then the timing of certain things that go on during the install and on the Mac side, and the several boot-reboot mount-unmount, episodes….etc., all this is exhausting just to say! It’s like a complex choreographed intricate dance with timing of steps that make or break it. Unexpected results happen and it takes some start-overs to get a seamless and smooth performance. After reading about what to do when the “booting into recovery” happens, it was all about repairing fhe OS. Well, it hasn’t been used yet! I was certain that it shouldn’t have happened on a new, never used system. Basically this recovery boot business is not something you want to “work through” with a brand new install. Even if I could fix it, who wants to start with a brand new system that had to be “recovered” before you ever made it to a desktop? I want my MBR and OS to be squeaky perfect new, not all bandaged up. And today my son came home to tell me again how incredibly fast and flawless it is working even running all the CAD programs. No surprises causing me to wonder if the OS was still “sick.”

      It takes way more time to troubleshoot the recovery issue than it does to just start over from scratch a few times until it gets it right. And when it does, it looks exactly like the instructions say it will. I know, I naively chose to troubleshoot the recovery thingy with my WD, and I did a “pppffffttt, ya right” with my T5 install choosing to just start over each time instead, and that install took wayyy less time.

      I realized with the Samsung T5 that it is very important to first install the drivers for the SSD (or HDD) on the Mac side and not trust whatever automatic install of drivers it does for you when you connect it. Sure the Mac OS can read it and work with it as is, but this VM install with mapping it can’t for some Macs or the newest OS, and I think the Airs are one of them. (Ours is 2015 Mojave) . Wrinkles happen that fresh correct drivers iron out. Magically. I know nondetails why..You HAVE to do this. I downloaded them from the manufacturer’s sites because the included drivers on the drives when new are bundled in a “setup” package that installs software too, more than I want. And one of the drives was already erased and formatted anyway so I lost the driver. I was able to download just the drivers from their sites and installed them.

      So, steps in order, I started clean again like this:

      -I located and downloaded just the SSD/HDD drivers. Set the aside and ready to install but not yet.
      -I deleted the vmdk file from my home folder.
      -then I deleted the VM completely from VirtualBox.
      -Then I reformatted my external drive as the instructions say.
      -I rebooted my MacBook Air
      -I installed the SSD drivers
      -checked readability
      -To be safe, I reformatted the SSD drive again after drivers had been installed. (I mean Mac OS is doing the reformat, so… And THIS time it automatically created that EFI partition for me! (Why? no clue. But now It was always created before going into VirtualBox and VirtualBox identified it correctly too. I didn’t have to set it.)
      -I started the steps all over again with a clean slate, skipping the bootcamp USB steps since that was already made, BUT, warning about the USB after this, it was my last roadblock and there is a fix…
      -I made sure to do all the same steps and tweaks and modifications that bypassed the first few rounds of troubles.
      -I got to the boot point pretty quickly, and that time it worked and booted to
      the desktop, no booting to recovery surprise.

      Now, Bootcamp USB Windows support. Windows COULD NOT READ IT!!! I had to reformat again and reinstall the bootcamp drivers from the Mac side again. I’m away from my notes right now, and foggy about the fix, so I’ll post back if I get it wrong, but something switched it from Master Boot Recird to something else, and I don’t know how, but it was no longer showing the MBR in Disk Utility. So I reformatted and redownloaded to the USB. Took longer than the Windows install. Lol Then Windows had no problem.

    • Ooops! My explanation of the Bootcamp USB wasnt quite right, but it is explained below in my post on January 26, 4:22 pm.

      I had to reformat the USB on the Windows side first, as a FAT32.

      THEN go back to Mac OS to put the bootcamp drivers on it.

  • Hi,
    I would like to use this workaround to access an existing Windows Vista OS on an old laptop HDD, rather than install an new version of the OS – what modifications should I make? I am running Mac OS High Sierra.

  • Hello. Thank you for the tutorial Tom. I need help with the name of my SSD. I selected to name my SSD “Win10” when formatting it for the install as you recommended at the very beginning of your tutorial. I’m done with the install and have no problems with Opt-boot and switching back and forth between the operating systems. However, my SSD says “untitled” in the Finder as it’s name/label. The Win10 didn’t stick through the entire install and something along the way removed it. Can I safely change the “untitled” to “Win10” without screwing up anything with the interface/installation on the MacOS side or the smooth running of Windows on the Win10 side? I don’t want it to get confusing with all the other drives we have, or have my son (who this is for) mistakenly think it is a unused disk one day.

    ADVICE OR HEADS-UP TO OTHERS about things that I ran into:

    I have a few other important solutions to problems I ran into that you might run into as well, and I’ll add another post detailing all of them as soon as I’ve finished with my install. But I’ll detail one of them right now because I’m knee deep into it as I type this and it hasn’t been mentioned anywhere below.

    I still need to get my bootcamp drivers loaded to my newly booted Windows system. I formatted the USB at the start of this process exactly as the tutorial said: MS-DOS FAT Master Boot Record. Just now Windows would not recognize the file system on the USB and kept asking to format it. This may be due to the more recent OS X versions. (I’m using Mojave.) Quoting “omheal” from a Reddit thread:

    The Disk Utility advanced options of El Capitan are hidden and you needed, first:

    -Quit Disk Utility.
    -Open the Terminal utility.
    -Run the following Command:

    defaults write com.apple.DiskUtility advanced-image-options 1

    -Relaunch Disk Utility

    -And now, just format your USB with MBR Partition (Master boot record) and exFAT file System.
    -The USB now can mount in OSX & Windows.

    I didn’t want to spend the time doing all that since I’ve been trying to get a successful install for FOUR straight days now, running into every single problem below as well as some new, never heard of before issues. Lucky me. I’m a magnet for glitches. So I just stayed in Windows and accepted its offer to format the disk and erase all my bootcamp files, and I formatted it as MS-DOS FAT32 from there. (I noticed it added 32 to the end.) It automatically makes it a MBR by default, so there is no setting for that. Then, I went back to my MacOS and it sees and writes to it no problem. I checked its format and scheme in Disk Utility, and sure enough, it says MS-DOS FAT32 Master Boot Record. I’m redownloading the files from Bootcamp Assistant right now. Crossing my fingers.

    I have some important answers to many problems below that went unanswered that I will provide, so that any new readers of this tutorial can be helped through those things if they run into them.

    If anyone can first answer my question at the top here I would appreciate it.

  • Followed all instructions. Windows installed to my USB3.0 HDD. When I star with option pressed only mu macos drive shows. Is this a Mojave issue?

    • No. I just finished mine on a MacBook Air with Mojave. The key to having it show is to make sure that EFI partition remains there when you install windows. It’s a little 200mb partition that is created when you initially format the hard drive as MS-DOS(FAT). I think that is when it’s created. You will see it when the Windows installer asks which drive to install to. There should only be two partitions showing if it’s a new drive or completely reformatted. Before starting the install, you have to make sure the Win10 VM’s settings in Virtual Box has EFT enabled. My reply to the comment just below (Jason) explains all that and how it impacts opt-boot. Hope it helps!

  • I have followed your walk through x3 now and when I go to reboot after the win install and hold the option button down, I only get my Mac HDD. So I boot up my Mac and go to Startup. The Win external drive is there and I select it and then restart forcing it to boot of the Win external drive. It results in with the “No bootable device” error. Any ideas?

    • Hi Jason,

      You’ll see several comments below detailing that exact problem. If my memory serves me correct, I believe it has to do with the formatting of the SSD, of which I ran into every problem with mine. It MUST have EFT enabled. You do this step when you are creating the virtual machine inside VirtualBox. I did it right after I selected the existing virtual hard disk file (.vmdk) to be pulled into the Virtual Machine. (Which is the first step in “Create a VirtualBox Virtual Machine for Windows”.) You go into settings and select EFT there. I think in the System tab, but it could be the General tab. Can’t remember.

      Just know that when you do option-boot, you will always see the drive as “EFT boot”. It will never say “Win10”.

      I also made sure at opt-boot to always select my network before booting windows so it wouldn’t have problems related to internet connection during the install. There were tons of reboots for me, so kind of a headache. I just now successfully got it installed (restarting this whole process from the beginning four separate times,) and there weren’t anymore restarts than in his tutorial (two I think?) when all the other issues are out of the way. I went straight through from the beginning to end in about 40 mins. After four days. Lol.

      Don’t be resistant to having to start over, delete the vmdk, scrap the VM, and reformat the SSD fresh, mapping the drive. It sounds more cumbersome than it really is. Goes much faster each subsequent time.

    • One other thing, Sven below shared, “I’ve done my own run of the setup and it works very well. My notes on change required are listed here: medium.com/@sv”

      It’s a necessary addition for this install that was priceless. I believe he covers the EFI with pictures too. Really great work on his part. I also have some additions to what he shares coming soon. In the meantime leave a post with any questions. I’m around.

  • Does this work on the 2018 MB Pro 15” and is it possible to also use the external drive as a storage device or is it only able to have the boot up on it??

  • ok, have followed your changes, and after installing windows,i reboot (in time) my mac with the alt-key, he shows 2 disks (OS and Windows) , select the windows-disk, and then a message shows up: . Any idea what i did wrong?

  • I have the same issue as Laura. The bootcamp.vmdk file is greyed out and stands also between quotes. Please can you help me?

    • You have copied the filename “bootcamp.vmdk” with fancy quotes, which is not valid. Remove that file, and try that command again without quotes.

  • I created the bootcamp.vmdk file in my home folder, but once I eject the external drive and go into VirtualBox and get to the hard disk sheet, I can browse to the bootcamp.vmdk file, but not select it (its greyed out). What I am missing??

    • there is a drop down menu that lets you not only select the .vmdk files, but al files. Same thing happened to me. After you select all files from the drop down menu, you will be able to select it.

  • Amazing reference. Thank you!

    I’ve done my own run of the setup and it works very well. My notes on change required are listed here: medium.com/@svenkirsime/install-windows-on-the-external-ssd-hdd-for-your-mac-5d29eefe5d1

  • So I get all the way up to the installing from the virtual box part. But once I select the ISO for the optical drive and start, I can’t get past the screen where it says “press any key to boot from CD or DVD…”

    Any suggestions?

  • Dude you realize can just download those programs from there respective website instead of using that which i think is a virus because there is no viruses that come with the program that are shown
    so i would stop using that website


  • I was able to get it all set up with a combination of tips from comments and the guide. Everything seems to work fine, but I can’t play any videos for some reason. Anybody than can help?

  • I am able to install the windows files onto the external HDD, however, when I try to boot from the drive (after shutting VirtualBox down before Windows is able to restart), I get a blue screen of death every time Windows tries to load, which then makes my computer restart. I’ve tried loading in safe mode, but same problems happens after loading “core files.” I wiped the external HDD and started over with the same outcome. Not sure what is wrong?? Any ideas or help? I’m using a seagate 1TB external HDD.

    • I’m having the same issue running Mojave on my iMac with Windows 10 Home on the external SSD. The BSOD error is DRIVER UNLOADED WITHOUT CANCELLING PENDING OPERATIONS and it happens when Windows is trying to complete setup while booted from the external. I’ve seen a lot of posts over the past week from other bootcamp users experiencing the same issue. Someone speculated that it may be related to the October Windows ISO.

    • I was having the same issue when attempting to install the October release of Windows 10 Home, but found I could successfully install the April release. Windows is running fine now, though I’m not sure what will happen if I attempt to update.

  • Windows10 is successfully running through the VM but when I restart my computer and hold down options the only option I am given is to select the mac startup disk and my wifi network. Any suggestions? Early thanks

  • Hi,

    I did everything listed here and everything worked fine. However when I restarted my macbook and went to the Startup, only my Mac drive showed up. My external hard drive didn’t show up. I re-did everything and I’m still getting the same thing

  • Hi

    Managed to get Win10 all up and running.

    Has anyone else come upon the problem that the April 18 Windows 10 update will not install on an external drive?

    Are there any workarounds to this issue?

    Many thanks

  • Thanks for the great step-by-step. I got this done and it totally works on my WD My Passport Ultra external drive!!

    I’ve gotta say that I got a bit bogged down in the Create a VirtualBox Virtual Machine for Windows section. I had to eject the external drive (remain plugged in) and eject and actually unplug the external drive a bunch of times until I was able create the virtual environment using the bootcamp.vmdk file. In other words, it took several of tries to make the bootcamp.vmdk file populate in the Storage panel in the Virtual Box Manager. I honestly can’t remember if it the external drive was ejected+plugged in or ejected+unplugged when I was successful. I don’t know if this was operator error or just something quirky.

    From then on it was clear sailing. Be sure to heed Tom’s advice on the “Windows needs to restart” bit.

    This is so cool—a way more functional Windows10 on my Macbook Pro than Parallels was.

    Thanks to Tom and Good Luck!

    • Hey Louie,
      Just wanted to know whether after installing W10 on your external drive you are still able to use it to store files in it like any other external drive.

      • You can but keep in mind you got the normal windows file structure (Users, Windows, Programs etc.) on the drive that should not be messed around with.

  • Hi.. i did everything right, apparently, got to start windows (7) on my Mac to complete instalation, but it enters an endless loop of restarting, even when I choose “secure mode”… what can I do? or what did I do wrong? Thanks

  • So I have managed to get everything in the installation processes to work up until Windows Setup. During Setup in the “Getting Windows Files Ready” part everything goes smoothly until 10%. At 10% the counter stops going up, the dot for drive activity turns solid red and nothing appears to happen. Does anyone know how to fix this?

  • Hi everyone,

    I’m wondering if I do this, will I later be able to store other things (like photos and videos) on the external hard drive for use from Mac through iPhoto/Photos? Are there additional steps that I will need to take to make this possible?

    Thanks in advance for the help!

  • Hello! Thank you for this awesome tutorial. Also thanks to the comments for the additions.

    I tried it, but unfortunately, whenever I try to start the virtual machine, I get the following error:

    VD: error VERR_RESOURCE_BUSY opening image file ‘/Users/daniel/bootcamp.vmdk’ (VERR_RESOURCE_BUSY).

    Failed to open image ‘/Users/daniel/bootcamp.vmdk’ in read-write mode (VERR_RESOURCE_BUSY).

    AHCI: Failed to attach drive to Port0 (VERR_RESOURCE_BUSY).

    I tried Vince S’ tip and ran “sudo chown MYUSERNAME:staff /dev/disk#”, of course with my username and the right disk identifier.

    Still, I get the same message every time. I also went to my home folder and in the info panel of my vdmk-file set “everyone” to read and write.

    What am I doing wrong? I would really appreciate help.

    Have a good day @ all!

    • Hey Daniel, I got the same errors, make sure the external drive is still unmounted (ejected) when trying to run the virtual machine. Other than that, try restarting your machine and checking to see if there are any flags in the security settings that you need to allow.

      Sorry, I can’t be more specific, I encountered about 3 errors and I can’t remember what fixed what, but those were the things I did

  • I have an issue here.

    I accidentally downloaded the WINDOWS SUPPORT to my desktop and NOT my USB. So, the authentication and verr access wasn’t properly done on the USB.

    This is my fault.

    But, how do I fix it? I went through all the steps, regardless (now I realize, I had done something possibly wrong.)

    This is the error I get when I add the Windows ISO to the virtual disk and I click Start:

    VD: error VERR_NOT_SUPPORTED opening image file ‘/Users/milespauling/bootcamp.vmdk’ (VERR_NOT_SUPPORTED).
    VD: error VERR_ACCESS_DENIED opening image file ‘/Users/milespauling/bootcamp.vmdk’ (VERR_ACCESS_DENIED).
    Failed to open image ‘/Users/milespauling/bootcamp.vmdk’ in read-write mode (VERR_ACCESS_DENIED).
    AHCI: Failed to attach drive to Port0 (VERR_ACCESS_DENIED).

    Is there any terminal commands I can apply quickly to be on my way?

  • I’ve followed every step and it works for me. But with the following additional steps:

    1. Before going to Terminal and map the external drive to the VirtualBox drive, EJECT the external drive first. Or you might have problems creating the bootcamp.vmdk file.

    sudo VBoxManage internalcommands createrawvmdk -filename “bootcamp.vmdk” -rawdisk /dev/disk4

    I typed the above command with quotation marks around bootcamp.vmdk. No problems.

    2. EJECT the external drive again prior to entering the subsequent terminal command to launch VirtualBox. Else you might get an access denied error.

    3. After creating a new VirtualBox drive pointing to the ISO, ensure you enable EFI (for special OSes) for this virtual drive.

    4. After starting the virtual drive, and in the Windows installation screen where you select the drive to install – DELETE the external hard disk (as it was previously set to MBR if you followed the instructions). After that, format the drive and Windows will create a GUID partition automatically for EFI. Then proceed with the installation.

    It should work now if you continue following the steps in the article.

  • Here’s what worked and didn’t work for me.

    I followed the steps up to restarting my mac except:

    1. I removed the quotation mark from this line of code: sudo VBoxManage internalcommands createrawvmdk -filename “bootcamp.vmdk” -rawdisk /dev/disk4 (thanks to the comments for this tip).

    2. I checked the box “Use Host I/O Cache” in VirtualBox. (Thanks to the comments for this tip also).

    3. When I formatted my external drive to NTFS before doing all of the steps, when I got to installing Windows, the installer couldn’t find my drive. When I formatted my external drive to MS-DOS (FAT) the Windows installer didn’t give me an option to format the drive but it still installed.

    4. When I restarted my mac with option pressed down my external drive showed up but when I entered I just got a black screen with a blinking underscore.

    5. Someone also commented that “Enable EFI (special OSes only) should be checked. I tried this but made no difference.

    Thanks everyone for the tips, but unfortunately I couldn’t get it to work. Is there something I’ve missed? Thanks

  • It does not work I keep getting the same error message in Terminal

    VBoxManage: error: VMDK: could not create new file ‘bootcamp.vmdk’
    VBoxManage: error: Error code VERR_ALREADY_EXISTS at /Users/vbox/tinderbox/5.2-mac-rel/src/VBox/Storage/VMDK.cpp(3392) in function int vmdkCreateRawImage(PVMDKIMAGE, const PVDISKRAW, uint64_t)
    VBoxManage: error: Cannot create the raw disk VMDK: VERR_ALREADY_EXISTS
    VBoxManage: error: The raw disk vmdk file was not created

  • I can’t boot the external win10 I made with this guide, through fw.
    I made the installation with usb.
    Is it because the win10 disk is MBR?
    Could this installation be done with GPT disk?

    • The windows installation complained about “being GPT” and it couldn’t install. I removed all partitions on the external drive, created a new partition and after that it worked

  • Tom,
    Why don’t you just correct the few mistakes in this guide?
    Like “bootcamp.vmdk”.
    And I would add, that you have to eject the WIN10 drive all the time.
    Next time, I’d also use chronological numbering in the steps, so it would be easier to point to them. (Now you have 9 different “step 3” ‘s in the mix…

    Nevertheless, this is the best guide in the web, rufus or wintousb guides didn’t work for me. And I don’t like to install trialware (9to5’s article used vmware/parallels, maybe because they have bought it?).

  • Hi, I’m amazed that the comments on this are still so recent – would be amazing if someone can give me a helping hand with this.
    I’m trying to get Win7 working from an external FireWire drive (Macbook pro mid 2009, OSX El Capitan). I’ve tried the tutorials here as well as the two below; the installation seems smooth either way and mac recognizes the external hard drive as windows drive after restart (holding option key). But after selecting the windows option, I end up with a “No bootable device – insert boot disk…” error


    2.https://apple.stackexchange.com/questions/225387/no-bootable-device-usb-2-0-macbook-pro-mid-2014/225521# (I’ve adapted the Disk and partition IDs to match my system)

    Would be fantastic if someone has experience with this and could give me a hint!


  • I tried doing this but it isn’t working, then I had to fix my partition schemes. Now I get this error…
    VBoxManage: error: VMDK: could not create new file ‘“bootcamp.vmdk”’
    VBoxManage: error: Error code VERR_ALREADY_EXISTS at /Users/vbox/tinderbox/5.2-mac-rel/src/VBox/Storage/VMDK.cpp(3392) in function int vmdkCreateRawImage(PVMDKIMAGE, const PVDISKRAW, uint64_t)
    VBoxManage: error: Cannot create the raw disk VMDK: VERR_ALREADY_EXISTS
    VBoxManage: error: The raw disk vmdk file was not created

    How do I delete this and start over?

    • I did delete the file but I still get…

      VBoxManage: error: VMDK: could not open raw disk file ‘/dev/disk10’
      VBoxManage: error: Error code VERR_RESOURCE_BUSY at /Users/vbox/tinderbox/5.2-mac-rel/src/VBox/Storage/VMDK.cpp(3416) in function int vmdkCreateRawImage(PVMDKIMAGE, const PVDISKRAW, uint64_t)
      VBoxManage: error: Cannot create the raw disk VMDK: VERR_RESOURCE_BUSY
      VBoxManage: error: The raw disk vmdk file was not created

  • Thank you for this great how to!!
    Somehow, I keep failing at this. This is the error I get when I try to “Create a VirtualBox Virtual Machine for Windows”. I receive this error:
    Failed to open the disk image file /Users/myname/bootcamp.vmdk.

    Could not open the medium ‘/Users/joelibby/bootcamp.vmdk’.

    VD: error VERR_RESOURCE_BUSY opening image file ‘/Users/muname/bootcamp.vmdk’ (VERR_RESOURCE_BUSY).

    Result Code: NS_ERROR_FAILURE (0x80004005)
    Component: MediumWrap
    Interface: IMedium {4afe423b-43e0-e9d0-82e8-ceb307940dda}
    Callee: IVirtualBox {9570b9d5-f1a1-448a-10c5-e12f5285adad}
    Callee RC: VBOX_E_OBJECT_NOT_FOUND (0x80BB0001)

    Any tips would be appreciated!

    • Hello Joseph,

      I just fixed this issue after a bit of tinkering. You need to assign your user ownership of the external disk.

      This can be done using this command:

      sudo chown MYUSERNAME:staff /dev/disk#

      (Fill in your username and disk number)

      Once you have done this run this command (do not run as sudo):

      VBoxManage internalcommands createrawvmdk -filename bootcamp.vmdk -rawdisk /dev/disk#

      (replace the # with your disk number)

      After this make sure the external drive is unmounted from MacOS and you will be able to add it to the Virtual Machine.

      Hope this helps!

    • Joseph,
      I got the exact same error as you did when trying to open the bootcamp.vmdk during the creation of the VirtualBox VM.

      Even though I ejected the external disk via the Finder in step 6 under the “Use VirtualBox to Install Windows on the External Drive” section… at sometime after step 1 in the “Use VirtualBox to Map the External Drive to a VirtualBox Disk” section, the disk got remounted in the finder. So just go back to the Finder and eject the disk again. Then re-try step 11 under the “Create a VirtualBox Virtual Machine for Windows” section.

      hope this helps someone.

  • Is it possible to do this but partition the drive so I could assign part of its storage to windows 10 and part to storing things from my mac (so MacOS)?

  • This is the error message I got:
    Last login: Sat Jul 21 10:05:56 on ttys000
    Johns-MacBook-Pro:~ johnscardina49$ sudo VBoxManage internalcommands createrawvmdk -filename bootcamp.vmdk -rawdisk /dev/disk4
    RAW host disk access VMDK file bootcamp.vmdk created successfully.
    Johns-MacBook-Pro:~ johnscardina49$ sudo /Applications/VirtualBox.app/Contents/MacOS/VirtualBox
    objc[2318]: Class FIFinderSyncExtensionHost is implemented in both /System/Library/PrivateFrameworks/FinderKit.framework/Versions/A/FinderKit (0x7fff96ea28b8) and /System/Library/PrivateFrameworks/FileProvider.framework/OverrideBundles/FinderSyncCollaborationFileProviderOverride.bundle/Contents/MacOS/FinderSyncCollaborationFileProviderOverride (0x1138e9dc0). One of the two will be used. Which one is undefined.
    objc[2318]: __weak variable at 0x7fe82ac4a4a0 holds 0x4031000000000000 instead of 0x7fe82ad656e0. This is probably incorrect use of objc_storeWeak() and objc_loadWeak(). Break on objc_weak_error to debug.

    objc[2318]: __weak variable at 0x7fe82ac2de70 holds 0x5e9 instead of 0x7fe82ad656e0. This is probably incorrect use of objc_storeWeak() and objc_loadWeak(). Break on objc_weak_error to debug.

  • The comments & follow-ups on this article have been extremely useful for me to chip away at a few issues I was having in trying to install Win 8.1 onto a USB 3 external drive …

    I’ve now got to the stage where I can dual-boot (N.B. at startup only ie still get bless tool error when chosing the folder in Start Up manager within System Preferences !) to a Samsung T5 from my MacBook Pro (15-inch, 2017) to finalise the install however …
    I immediately get a BSOD stating :-

    Your PC needs to be repaired
    The Boot Configuration Data file is missing some required information
    File: \BCD
    Error code: Oxc0000034

    Any ideas or pointers, anyone ?

    • Hi Bill, I had the same issue and solved it by NOT shutting down the virtual machine before the first restart but waiting until it restarted and showed the Windows customize/setup screen. Then I powered off, restarted the MAC and finished the WIN installation. Now everything works just fine.

  • Hi, I tried to do everything right,
    I’m not sure if this caused my problem – but I used Paragon to NTFS format instead of FAT-32.
    Anyways, I couldn’t see my drive in macOS’s Drive Selection during boot up. I used rEFInd/refind and tried to boot into the drive, only to see the error found in this video: youtube.com/watch?v=-apCn91eVIs

  • Hi,
    I did everything right, windows boots fine, but I cannot complete the installation process (and subsequently install the drivers). In fact, the keyboard or the trackpad don’t work and hence I can’t click on next or anything to finish off windows installation. Any ideas?

    I have a new MacBook Pro 15’’. Could it be that the hardware is not compatible and needs drivers? If so, can you think of a workaround?

  • Hi–I installed to the external drive and closed VMware before it could restart. When I restart my computer and held down the option key, only Macintosh HD appeared as a choice. Not sure what I did wrong. Can anyone help?

    • I tried using the “Startup disk” to manually select the windows boot drive but it says “The bless tool was unable to set the current boot disk”

  • And yes, I tried 9to5 mac procedure using vm ware fusion 10 and Teyadi external ssd. It didn’t work for me. Windows 10 in vm is unable to identify the external ssd. Seems some kind of problem with VM ware drivers or windows drivers but it won’t appear in explorer or disk management. There is yellow exclamation mark as well in the device manager. So, this workaround is surely better for those who can’t get the former work for them.

  • Have finally been able to install win 10 pro. This is difficult for novices. Above mentioned steps will work well with moderate users. A video tutorial or snaps alongwith steps will be very much helpful.

    I found trouble in following areas:

    Couldn’t locate the ‘home folder, initially. On mac, go to users and the folder (probably computer name in windows) is your home folder. Will be displayed as home icon.

    There is an error in the code where you have to create bootcamp.vmdk through terminal. Please ensure that you don’t use quotation marks in the code. If you have anyway, then go to home folder and remove the quotation marks by (rename the file).

    Couldn’t get the installation started in vm right away, it gave some error ‘FATAL: No bootable medium found! System halted’. Go to storage, remove any ’empty disks attached to any sata port and ensure that there are only two, one is bootcamp.vmdk and other is your iso file. First one is at SATA 0 and other is at SATA 1 (if you don’t have any more drives). Then go to system and change the boot order by prioritising optical disk over floppy or hard disk.

    Trackpad and bluetooth are still not working. Track pad doesn’t click or right click and unable to pair Logitech mouse through blue tooth. Will update as soon as I find solution to this.

    This helped me.

    • Regarding trackpad not working(soft click), its some sort of problem with windows 10 user accounts.
      Go to user accounts, create another account (administrator), log off from your default administrator account, log in to your newly created administrator account, go to user accounts and change the default account from administrator to standard. Now log in to your default (now standard account) and bootcamp control panel in the task bar should work fine. After the trackpad, you can again change account to administrator, if needed.

  • I am unable to select the bootcamp.vdmk file. The Virtual box software has been moved to Oracle’s site and appears to have been updated. Is there a way to use the app to create a .vdmk file? It wants to know if the choice should be dynamic, fixed or split.

  • Hey, i got a problem with boot camp assistant. it only shows me the option for partition and installation of windows. there is no such thing as “download the latest windows support…” where else can i find the correct windows installer and drivers??

  • Solution to VERR_FILE_NOT_FOUND: you must open Disk Utility to eject only the disk volume (not Finder). For example, if the physical disk is represented by disk3, eject only what is represented by disk3s1.

    • this is what I get “VBoxManage: error: Cannot open the raw disk ‘/dev/disk3’: VERR_FILE_NOT_FOUND
      VBoxManage: error: The raw disk vmdk file was not created”

      I ejected the disk3s1 and it still doesn’t work