Boot Windows 10 On External Drive Mac

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.

How to Create a macOS Boot Drive In Windows Using TransMac. Let's create your macOS boot drive. With your USB flash drive still connected to your Windows computer: Load up TransMac and run the application as an administrator; On the left-panel, select your USB flash drive and right-click the drive. Then select Restore with Disk Image. In order to make external hard drive bootable Windows 10, you need to format external hard drive at first. Step 1: Insert the external hard drive into your computer. Type cmd in the search box and right-click Command Prompt and choose Run as administrator to continue.

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.

Nov 17, 2020 An external USB flash drive with a storage capacity of 16GB or more, unless you're using a Mac that doesn't need a flash drive to install Windows. A 64-bit version of Windows 10 Home or Windows 10 Pro on a disk image (ISO) or other installation media. The cloned external drive is now a windows boot drive. You can now remove bootcamp from the internal drive using the bootcamp assistant. Now boot from external drive and resize the bootcamp sector using Windows disk management tools to the full hard-drive size (keeping efi sector). Job done dual boot external Windows tb3 drive. Step 3: Dual-Boot Mac OS and Windows 10 using Clover. The last step is be able to boot boot Windows 10 and Mac OS using Clover EFI Bootloader to do that follow Step 5 & 6 of this guide: Hackintosh Dual Boot Windows 10 and macOS High Sierra (Same Drive) Hackintosh Dual Boot Windows 10 and macOS High Sierra (Same Drive).

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

Boot Windows 10 On External Drive Mac 11 5

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.

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.

  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.

  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.

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.

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.

  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.

Related Links

Other topics you might like:

Many people choose an Apple computer because of its reliability, but like any computer, Apple Macs can experience boot problems that prevent them from loading up. There are a number of reasons why Apple's operating system macOS may not load correctly. This includes file corruption, incomplete software updates, hard drive failure, power supply issues and other hardware issues.

Hardware issues can be a little harder to diagnose and resolve, though they are thankfully less common. Most boot problems are caused by system files being corrupted so all you have to do is repair or restore your operating system using a macOS boot drive.

In this article, I will show you how you can create a macOS boot drive in Windows using an application called TransMac. This is useful if you don't have a macOS boot drive or don't have access to another Apple Mac computer.

What You Need to Create a macOS Boot Drive

In order to create a macOS boot drive using Windows, you will need three things:

  • A USB flash drive with at least 16GB of storage
  • A copy of TransMac
  • The latest version of macOS
Drive

TransMac retails at $59 USD, however, the software is free to download and use for 15 days. You only need to upgrade once the 15 evaluation period has expired.

The Apple Downloads page has DMG files for Mac OS X Lion, macOS Mojave and macOS Catalina. Be sure to download the version of macOS that is compatible with the Apple Mac you are trying to fix.

Once you have downloaded TransMac and the macOS DMG file, you can prepare your USB flash drive.

Creating a GPT Partition On Your USB Flash Drive

The first thing you need to do is create a GPT partition on your USB flash drive. GPT is also known as the GUID Partition Table.

To do this, you need to connect your USB flash drive to your computer and load Command Prompt. This can be done by entering CMD or Command Prompt in the Windows search bar at the bottom right-hand side of Windows. Be sure to select Run as Administrator when launching Command Prompt.

Once Command Prompt has loaded, enter this command:

This command loads the command-line disk partitioning utility Diskpart. This allows you to locate your USB flash drive using the list disk command.

At this point, Diskpart will show all drives. This allows you to see which disk corresponds to your USB flash drive.

In the command below, X refers to your USB flash drive. For example, select disk 3.

Using the clean command, you can now delete all files on your USB flash drive.

Next, you need to convert the flash drive from MBR to GPT. You can do this using the command convert GPT.

Finally, you can create a new partition using the command create partition primary.

Your USB flash drive is now ready to be used with TransMac.

How to Create a macOS Boot Drive In Windows Using TransMac

Let's create your macOS boot drive.

With your USB flash drive still connected to your Windows computer:

  1. Load up TransMac and run the application as an administrator
  2. On the left-panel, select your USB flash drive and right-click the drive. Then select Restore with Disk Image.
  3. You will then be asked which disk image to restore. Select the DMG you downloaded earlier from the Apple Downloads page.
  4. Wait until the DMG file has been fully flashed to your USB drive. This process can take a few hours.

Congratulations. You have now created your macOS boot drive. It can now be safely ejected from your Windows computer.

Please check out the video below to see all of these steps in action.

Booting Up Your Mac Using Your macOS USB Boot Drive

Now that you have created your macOS boot drive, you can insert the USB flash drive into the computer you were having problems with.

To boot up your Apple Mac computer, you either need to hold your computer's power button down until the startup screens load or you need to power on your computer and then hold the Option (Alt) ⌥ key. Which method you use depends on whether your Apple Mac uses an Apple CPU or an Intel CPU.

Mac

As per the instructions on “How to create a bootable installer for macOS“:

Apple Silicon

  1. Plug the bootable installer into a Mac that is connected to the internet and compatible with the version of macOS you're installing.
  2. Turn on your Mac and continue to hold the power button until you see the startup options window, which shows your bootable volumes.
  3. Select the volume containing the bootable installer, then click Continue.
  4. When the macOS installer opens, follow the onscreen instructions.

Intel Processor

  1. Plug the bootable installer into a Mac that is connected to the internet and compatible with the version of macOS you're installing.
  2. Press and hold the Option (Alt) ⌥ key immediately after turning on or restarting your Mac.
  3. Release the Option key when you see a dark screen showing your bootable volumes.
  4. Select the volume containing the bootable installer. Then click the up arrow or press Return.
  5. If you can't start up from the bootable installer, make sure that the External Boot setting in Startup Security Utility is set to allow booting from external media.
  6. Choose your language, if prompted.
  7. Select Install macOS (or Install OS X) from the Utilities window, then click Continue and follow the onscreen instructions.

If you're not sure which type of CPU your Apple mac uses, simply try loading up by holding the power button in. If that doesn't work, you can load up by powering up and holding the option key.

Final Thoughts

As you can see, creating a macOS boot drive in Windows is straightforward. All you have to do is prepare your USB flash drive correctly using Diskpart and then flash the macOS DMG file to your drive using Transmac.

If you run into any problems, go back to the start and run through all steps again. This will ensure that no part of the process has gone wrong. Be sure to watch my detailed YouTube tutorial about creating a macOS boot drive using Windows too.

Good luck.

Kevin