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Bootcamp, Windows 10, VirtualBox, External Drive

Windows 10 on a Mac external SSD


Mac users have had the ability to run Windows natively on their mac with Bootcamp or Parallels for a while now.  It works great as long as you've got the hard drive space to house two operating systems and all of their data.  For many of us though, that's just not the case.  

For instance, my mid-2015 macbook pro only has a 250 Gigabyte hard drive.  Of that, only about 50 Gigs are free, so partitioning and running windows would completely tie up all of my internal storage.  What to do?  Put the Windows operating system on an external drive, of course!

But, won't that run super slowly? 

Good question.  Yes.  It would run super slowly if you tried installing it on a normal external hard drive.  That's why you'll need one of these super fast, super portable external ssd drives:


These drives are small and light enough that they'll dangle from your macbook if that's something you're worried about.  They don't weigh enough to pull loose.  They're also all really fast.   So fast that running windows on one will be basically the same as running it on your internal drive.

If you're buying one, they each cost around $80 at the time of this writing.  My pick was the SanDisk.  It's super fast and it's so light and thin that you can literally carry it in the tiny pocket above the normal pocket of your jeans.  You know, that formerly useless 5th pocket?  If you already own one of the others though, it'll work just fine -- you'll just have to put it in one of your "normal" pockets.  Be forewarned though, you'll need to offload anything that's on that drive, because it will need to be completely reformatted (a few times actually...).

Some other things you'll need in order to make this happen:

  • A mac (Duh!)  Older ones will work as long as they're intel-based.  Note that I'm using a mid-2015 macbook pro.
  • VirtualBox for Mac  It's free!
  • USB flash drive with at least 3Gb of free space on it.  You can probably find one of these lying around, but if you need to get one, they're pretty cheap.  Here's one on amazon for 9 bucks.
  • Windows ISO - This is free.  You can purchase a license if you like, but there's very little difference between the activated and the non-activated versions.  This is a big file and takes a while to download, so go ahead and get started.  IMPORTANT:  When selecting the edition of Windows 10, choose the April 2018 edition.  I tried this with the October edition and it doesn't work.  I think their official ISO for the October version is corrupted.  It works great with the April version though.
  • For Desktop Macs Only:  You'll need a wired keyboard and mouse.  You won't be able to use your wireless / bluetooth keyboard and mouse to complete the install.  Once the install is complete, they will work, but you'll need to plug in to finish the installation.  If you're using a laptop like me, this won't be a requirement.  Your keyboard and trackpad will work to complete the installation.


Ok, got everything you need?  Let's get started.

Step 1:  Set up the USB flash stick

Put your flash stick into a usb slot on your mac.  Press command and space at the same time to bring up spotlight search, and type in Disk Utility.  Open the Disk Utility program.  Make sure to go to the menu up top and select View->Show All Devices.  

Now select your USB stick -- the main one which is generally the manufacturer's name.  Don't make the mistake of selecting any partition below that.

Now click Erase at the top of the window and choose 

  • name: UNTITLED 
  • Format MS-DOS (FAT) 
  • Scheme: Master boot record


Format USB flash drive

Click save and then open up boot camp assistant by pressing command and space at the same time to bring up spotlight search and typing boot camp.  Open the boot camp program.  Go up to menu and select Action->Download Windows Support Software. 

Download WindowsSupport Files

This will ask you to save the windows support files.  Choose to save them on your USB flash drive and click Save.

Save to USB flash Drive

This will take a while.  Once it nears completion, you'll be prompted for your admin password.  Enter it and save the support files.  Your USB flash drive should look something like this:

USB Flash Drive Contents


Step 2:  Set up the external SSD

Press command and space at the same time to bring up spotlight search, and type in Disk Utility.  Open the Disk Utility program.  Make sure to go to the menu up top and select View->Show All Devices.  

Now select your external SSD -- the main one which is generally the manufacturer's name.  Don't make the mistake of selecting any partition below that.

Now click Erase at the top of the window and choose 

  • name: WIN10 
  • Format MS-DOS (FAT) 
  • Scheme: GUID Partition Map

If you are asked whether you want to use the disk as a time machine backup, click ‘Don’t Use’.  Then click Done.

Now you'll need to open up your terminal application.   Command and space to bring up spotlight search and type `terminal`.  That will bring open your terminal.  If you're not familiar with terminal that's fine.  Just paste in the following commands and all should be fine.

First we'll want to find the system name for the external SSD.  Type this without the back ticks:

`diskutil list`

This will output something similar to what you see below:

diskutil list output

See the highlighted `/dev/disk2`?  That's the system name for my External SSD.  You can see that it is 250 Gb, and has 2 partitions:  EFI and WIN10.  This is because it's a GUID Partition Scheme.  The EFI partition makes it bootable on a mac... We'll get to all of that in a few minutes.  The important thing for now is that you save the system name (for me, /dev/disk2) as we'll need it momentarily.

For now, unmount (eject) your SSD by looking in the Finder sidebar and clicking the eject icon, or by finding the drive's icon on your desktop and dragging it into the trash.

Now enter this command in the terminal (without the back ticks)

`sudo VBoxManage internalcommands createrawvmdk -filename bootcamp.vmdk -rawdisk /dev/disk2`

Make sure to change the last part from /dev/disk2 to /dev/<whatever your disk number was>.  You'll be prompted for a password.  Type your admin password and press enter.  You should see a message telling you that bootcamp.vmdk was successfully created.  If you get an error, chances are you forgot to eject your SSD.  This process will re-mount your SSD, so you'll need to unmount (eject) your WIN10 disk again.

Back in terminal again, enter the following without the back ticks:

`sudo /Applications/`

If prompted, type your admin password again and press enter.  This will open up VirtualBox, and allow it to run with permission to access your external SSD.

In VirtualBox, click the `New` Gear icon and enter the following

  • Name: WIN10
  • Type: Microsoft Windows
  • Version: Windows 10
VirtualBox setup

Click continue, and keep the memory size default of 2058Mb. Click continue again, and choose `Use an existing virtual hard disk file`.  Click the folder icon to the right of the pull-down, navigate to your home (~) directory and choose the bootcamp.vmdk file.  Click Open (NOTE:  If you haven’t unmounted (ejected) your WIN10 external drive, you will get an error here.  Just eject the drive and try again)

Finally, click Create.  You now have the WIN10 virtual machine.  

Now, back in terminal open a new tab with command-T and type (without the back ticks)

`sudo VBoxManage setextradata WIN10 “VBoxInternal/PDM/HaltOnReset” 1`

Type your admin password and press enter.  This will prevent the Virtual Machine from rebooting later in the process which trust me, is important.

Back in VirtualBox, Make sure the WIN10 virtual machine is selected, and click the `Settings` gear icon.  Click the `System` icon at the top.  At the bottom of the System section that opens, check the `Enable EFI (special OSes only) box.  Click OK to save changes

Now click the `Settings` gear again, but this time choose the `Storage` icon at the top.  In the left hand side under `Storage Devices`, click the DVD icon that says `Empty`.

Configure VM Storage

Then in the right hand side under Attributes, Click the DVD icon, and select `Choose Virtual Optical Disk File…`.  Navigate to your Desktop (or wherever you saved your windows iso file), select the iso file, and click open.

It should now show up next to your DVD icon in the left hand side. Click Ok to save changes.

Add virtual optical disk


Now we are ready to install windows on our virtual machine.

In VirtualBox, ensure that the WIN10 machine is selected and click the `Start` arrow to begin the installation

Note, you may need to press any key when the Virtual machine first starts up.  It can be hard to see this, as there may be some windows relating to mouse capture that pop up to obscure it.  If you miss pressing any key, you may boot into shell mode.  If this happens (i.e. your screen doesn’t look like the following image) then you can simply close the WIN10 machine window, select Power Off Machine, and then try again by selecting the WIN10 machine, and clicking Start again.

Windows Installation Screen

Click Next, and then click Install Now.

Wait a few moments, then accept the license terms and click Next.  Now choose the `Custom: Install Windows only (advanced)` installation option.

NOTE:  The first time I attempted this, I had downloaded the October 2018 version of the Windows 10 .iso file.  At this point in the process, I received an error saying that I was missing media files that were required by Windows.  After spending way too much time trying to figure out why this was happening, I decided to try downloading the April 2018 version of the .iso file and trying again.  April works, October doesn't. 

Now you’ll see a list of drives where windows can be installed.  If you checked the EFI option under System settings in the virtual machine setup, then you’ll see two partitions:  An EFI partition that Mac needs to boot from this drive, and a much larger WIN10 partition where we will install windows.

Windows Drives List

Click the WIN10 partition.  This partition isn’t formatted correctly for Windows 10.  (Mac’s disk utility can’t format the drive properly for windows 10).  So after you select the WIN10 partition, click the Format link

Make sure you’ve selected WIN10 and not the EFI partition, and click OK.

Now with the WIN10 partition still selected, click Next.  Now windows will install itself onto your drive.  This may take a few minutes.

Windows Installation Screen

Once it finishes, Windows will attempt to restart.  It won’t be able to restart though as we prevented it with a terminal command earlier.  When all you see in your virtual machine window is a blank blue screen like so:

Windows Blue Screen

Close the virtual machine window by clicking the red close button in the upper left-hand corner of the window.  Select the `Power off the machine` option and click OK.

Power off virtual machine

Now you are ready to boot into Windows and complete the installation.

Restart your Mac, and hold down the option key during restart.  This will bring up a list of drives that your Mac can boot from.  Choose your WIN10 drive to boot into Windows.

Now Windows will boot up and begin installing components.  You’ll see a windows logo and a spinning circle.  After a while, windows will reboot your machine.  It’s very important that you be there to press and hold option when this happens.  Otherwise, it will boot back into Mac.  

Using the arrow keys on your wired (or laptop) keyboard, select the EFI boot drive again and press enter.  You’ll see the same windows logo and spinning circle as before.  After a while, you’ll be asked for Region and keyboard layout.  

You can skip the network setup as we don’t have the proper drivers installed yet.  Set your privacy preferences as you wish and eventually after all the setup panes, you’ll be looking at the windows desktop

Now we install the drivers to get all of our Apple hardware to play nicely with Windows.

  • Make sure the USB flash stick that you put the bootcamp files onto is connected to your Mac.
  • Click in the ’Type here to search’ bar at the bottom of your desktop and type File Explorer, hit return to open file explorer.
  • In the File Explorer sidebar, select the USB flash drive, it will probably have a D or E drive letter assigned to it.
  • Inside the flash drive, open the Boot Camp folder
  • Double-click the Setup.exe file inside the Boot Camp folder.
  • Follow the onscreen instructions to install the Boot Camp drivers.

Once the installation completes, you’ll be asked to restart windows.  Do so now, and remember to hold down the option key.  Select the EFI boot drive once more and boot back into windows.

Now all your Apple hardware, including wireless keyboards and mice, should be working.  Feel free to connect to your network, and start enjoying your new Windows machine!