How to Boot a USB Flash Drive in VirtualBox

Make VirtualBox Boot from USB Flash Drive (Windows)

1. Download and run VirtualBox (Installing to the default path).
2. You’ll need to use the command line to perform steps 3-6,
   To open a command prompt;
   (1) From the Windows ‘⌕ Type here to search’ box, type cmd.exe
   (2) Then click Run as administrator
   
3. At the command prompt, type diskmgmt.msc and press Enter to open the Windows Disk Management Tool. Then, identify your USB Disk #
   
4. Now, back at the command line, type

   cd %programfiles%\oracle\virtualbox

5. Replacing # with your USB Disk number from step 3, type

   VBoxManage internalcommands createrawvmdk -filename "%USERPROFILE%"\.VirtualBox\usb.vmdk -rawdisk \\.\PhysicalDrive#

6. To start VirtualBox as Admin, type start virtualbox
7. Click New, and then proceed to Create a New Virtual Machine.
   
8. When prompted for a Virtual Hard Disk, tick use existing hard disk. Then, browse to your %USERPROFILE%\.VirtualBox folder, and select the usb.vmdk file.
   
9. Once done creating your New Virtual Machine, click Start.
   

If all goes well, VirtualBox should now be emulating, booting, and running your USB device from within Windows.

Getting Persistence to work in VirtualBox (Windows)

At first the USB flash drive might not work exactly like it does when booted natively. Things like Ubuntu’s casper persistent feature won’t work. Some distributions might not even boot, or will boot with errors. This is because the volumes on the device are mounted by Windows, preventing VirtualBox from gaining full access. In order to fix these issues, you can use a tool called LockDismount. Then simply run the tool (using the following steps), prior to starting the Virtual Machine that is tied to your USB.

1. Download the LockDismount tool
2. Launch the tool right before starting your VirtualBox VM
3. Select your USB from the drop-list, then Press Lock it!
   (optionally you can check Force Dismount)

Now your flash drive should be able to boot in VirtualBox exactly as it does when booted natively on a physical machine. ;)

Make a VirtualBox Bootable USB Flash Drive (Linux)

The following process to boot a USB flash drive in VirtualBox was performed from a running Ubuntu Operating environment. This method should also work for Debian and other Ubuntu Linux based Operating systems.

1. Open a Terminal Ctrl+Alt+T, and then type the following and press Enter;

   sudo apt install virtualbox

2. Next, type

   sudo fdisk -l

   (note which device is your USB drive I.E. /dev/sdx)
   

3. Replacing x with your actual device letter found from step 2, type

   sudo vboxmanage internalcommands createrawvmdk -filename ~/usb.vmdk -rawdisk /dev/sdx 

4. Type sudo virtualbox to start the program, and proceed create a New Virtual Machine.
   
5. When prompted for a Virtual Hard Disk, tick use existing hard disk, then browse to your Home directory and select usb.vmdk.
   
6. Once you’ve finished creating your New Virtual Machine, click Start.
   

If all went smoothly, you should now be able to boot a USB flash drive from VirtualBox on the Linux Host.

Boot a USB Flash Drive in VirtualBox (Mac OS X)

1. Download and install VirtualBox for OS X Hosts via the .dmg file.
2. Open a Terminal, type the following and then press Enter

   diskutil list

   (make note of which disk is your USB drive I.E. /dev/disk#)

3. Replacing # with the disk number of your USB drive, type

   diskutil unmountDisk /dev/disk#

4. Again, replacing # with your actual disk number, type

   vboxmanage internalcommands createrawvmdk -filename ~/usb.vmdk -rawdisk /dev/disk# 

5. Once more, replacing # with the disk number, type

   diskutil unmountDisk /dev/disk#

6. Finally, to start the program with root access, type

   sudo virtualbox

7. Next, Proceed to create a New Virtual Machine.
   
   When prompted for a Virtual Hard Disk, tick use existing hard disk.
   Then, browse to your Home directory and select usb.vmdk.
   
8. Once finished creating your New Virtual Machine, click Start.
   

You should now be able to boot a USB flash drive in VirtualBox on the Mac OS X host, while retaining the ability to boot from the drive natively as well.