Booting from USB devices in virtual box

https://forums.virtualbox.org/viewtopic.php?p=14118

Problems with older versions of virtual box

Direct booting from an USB device is not possible with VirtualBox as this requires USB support in the BIOS which we don't provide.

It is not passible directly but it is possible indirectly. Configure your USB drive as a raw disk in VirtualBox (page 105 of the manual). Then the guest will see your USB drive as a IDE drive and will be able to boot on it.

---------------------------------

RAW access isn't possible under NT6 (Vista, Server 2008 and Seven), because MS restricted it ... To avoid this Sun has to implent a driver which enables the option again ...

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I can confirm that the plop manager does work outside of the virtual environment (I used to from a CD ][iso file] to boot from USB on an old motherboard)

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Works great in VMware, other machines etc so I'm attributing it to VB environment.

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Jul 2010

Made it work on VB 3.2.6 (non OSE) without freezing at the host 1 message.

Just had to enable the USB support (without enabling the USB 2.0 box in the settings window).

---------------------------------

I came up with this method for booting virtual box guests from USB devices a while ago. It works for me but might not work for others...

This guide contains a method for creating a Bootable CD that includes the Linux kernel and some other stuff including the USB driver needed to use a bootable USB device. This CD boots up and loads the USB driver then continues the boot process from any USB device.
This CD (iso file) can be used to boot a USB HDD in VirtualBox.
After creating a new virtual machine, select the USB section of that device’s settings and add a new USB device which would be the USB HDD. Then start the machine, boot from the bootable CD created before, and then the boot process continues and the OS found on the HDD would load.
Notes

The boot CD might not detect the USB HDD if the UUID tip in the guide’s comments was not applied.

Saving the machine state doesn’t work.

---------------------------

Bingo! "Enable USB 2.0 (EHCI) Controller" must be un-checked before USB Booting will work with the PLOP iso. I've noticed that although it works, it reads from the usb key slowly.

 If anyone has a clue on how to fix the speed issue then everything would be working perfect!

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I've got a bootable USB drive which contains (X)Ubuntu Linux, ie a kind of portable Ubuntu Linux. Boots well natively with the help of the PC's BIOS.
As suggested earlier in the forum, with the help of a Virtualbox command creating a small ".vmdk" file (which points to that USB drive), you can also boot the USB drive's Linux from within Virtualbox.
However, the Windows user account which runs Virtualbox needs Administrator rights in order to use the vmdk file.
On some Windows XP machines I've got Virtualbox running without Administrator rights and I still would like to boot this USB drive from within Virtualbox, but it won't work.
Is it possible?
To these Virtualboxes there's also attached a small virtual harddrive (real .vdi file) with a mini Xubuntu Linux. This could act as a starter. But how would you edit the GRUB2 loader so that it loads an USB driver and then boot from the USB drive (USB ports are enabled in the Virtualbox) ?
To be more clear: When I boot the mini Xubuntu from the virtual harddrive, at boot time there's no USB device available, but if Xubuntu has been loaded I can see and access the USB drive. So there must be some USB driver which sees that USB device within Virtualbox?
(P.S. PLOP within Virtualbox doesn't work on that USB device. No matter of USB 1 or 2 setting. It just hangs, like some posters already noticed.)

---------------------------

Here is a much easier and better way to get a USB drive to boot in a Virtual Machine. 
1. Go to http://www.plop.at/en/bootmanagerdl.html , and download the most recent .zip . 
2. Extract it, and navigate to /intsall/plpbtin.iso . 
3. Add the ISO in the VM, and install PLoP to the virtual hard disk (option 1)
4. Now, when you turn on the VM, it gives you an option to boot USB, Floppy, Hard Drive, and CD.

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There is a guide to do it easily with VirtualBox 4:

http://www.dallagnese.fr/en/computers-i ... tualbox-4/

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I have v4.04 on W7 and have installed the same version of the Extensions. The USB thumb drive is in fact disk 2 according to disk administrator. I've also tried adding it with and without the USB section of Settings configured for the device, and with and without USB 2.0 being checked there. I even tried creating a second vmdk for another device, but no go.

# Disk DescriptorFile
version=1
CID=e1212ff4
parentCID=ffffffff
createType="fullDevice"

# Extent description
RW 3948544 FLAT "\\.\PhysicalDrive2" 0

# The disk Data Base
#DDB

ddb.virtualHWVersion = "4"
ddb.adapterType="ide"
ddb.geometry.cylinders="3917"
ddb.geometry.heads="16"
ddb.geometry.sectors="63"
ddb.uuid.image="46c5e09d-34c9-49fb-9f07-365ee7c21657"
ddb.uuid.parent="00000000-0000-0000-0000-000000000000"
ddb.uuid.modification="00000000-0000-0000-0000-000000000000"
ddb.uuid.parentmodification="00000000-0000-0000-0000-000000000000"

Reason of failure
If you are using Vista/Windows 7, due to access limitation rights you should run the VB with admin credentials. And it should work.
============================

http://agnipulse.com/2009/07/boot-your- ... irtualbox/

VirtualBox is a free and easy to use multi-platform Virtualization software.

It means you can run a different OS inside your current OS (Linux in Windows, Windows in Linux, Linux in Linux, Windows in Windows, almost everything is possible!).

Linux in Windows

It is very easy to start a new virtual machine and use space on a virtual hard drive on your local hard drive (or USB drive). Just follow the VirtualBox wizard.
However, some people want more portability in the physical meaning. To have a system that you can put in your pocket, bring anywhere, plug into any computer and it will run YOUR system.

This is possible by installing a system on a USB stick! This guide won't explain how to install an OS on a USB stick but how to boot on this USB disk in VirtualBox.

Sometimes you don't want to boot on your USB stick directly but within another running system. Then, you need to run the system in a Virtual Machine.

Unfortunately, VirtualBox doesn't allow you to boot from the USB from the GUI.

Nevertheless, there is a small trick to make it possible, using only a single built-in VirtualBox command-line tool.

Let see how to do so in this tutorial!

This tutorial is largely inspired by the Boot your USB Drive in VirtualBox tutorial by AgniPulse, only updating it to the last current version of VirtualBox (4.0).

I assume you have:

• a bootable USB stick/drive with the system you want to boot on
• VirtualBox installed with the Expansion Pack (to support USB2 devices)

First, we need to know what is the device ID of your USB. Plug your USB in.

If you are running VirtualBox on Linux, the USB ID will be something like /dev/sdx (for example /dev/sdb for me).

On Windows,  you can see it in the "Disk Management".

Start typing "dsk" after entering the Start Menu and choose Create and Format Hard Disk Partitions:

Create and format disk partitions

Then you will have a page where you can identify the device number of your USB stick or drive.

In my case, my 8GB USB stick is on the Disk 1:

Disk Management

Note that on Ubuntu with VirtualBox 4.0.4 OSE (Open Source Edition): Make sure that you remove the USB device from the "USB Device Filters" list in the machine's settings (thanks Tim).

Now we are ready to create a Raw Virtual Machine Disk that will link to our USB stick.

Simply open a terminal on linux or a command-line tool on Windows (Win+R cmd) and change directory to your VirtualBox folder.

cd "C:\Program Files\Oracle\VirtualBox"

Then we run the VBoxManage command with the following options to link the USB Drive to a vmdk file (Virtual Machine Disk):

VBoxManage internalcommands createrawvmdk -filename output_usb.vmdk -rawdisk path_to_usb

You need to change the two red color highlighted parts to YOUR settings.

For example on Linux if I want to save in /home/thomas/.VirtualBox/usb.vmdk a virtual machine disk that links to my USB in /dev/sdb, I type the following line:

VBoxManage internalcommands createrawvmdk -filename /home/thomas/.VirtualBox/usb.vmdk -rawdisk /dev/sdb

On Windows, if I want to save the virtual machine disk in C:\Users\Thomas\.VirtualBox\usb.vmdk that links to my USB in in Disk 1 (according to the previous Disk Management), I type the following line:

VBoxManage internalcommands createrawvmdk -filename C:\Users\Thomas\usb.vmdk -rawdisk \\.\PhysicalDrive1

Replace the 1 in \\.\PhysicalDrive1 by YOUR device number os the USB drive (for example \\.\PhysicalDrive2).

Note: As noticed by Carlet, if any path contains spaces, write it between quotation marks (") to make it work.
Example: VBoxManage internalcommands createrawvmdk -filename "C:\Documents and Settings\Carletdesiles\.VirtualBox\usb.vmdk" -rawdisk \\.\PhysicalDrive1

Note: As noticed by Alex and skydvr, on Windows Vista/7, you need to start the command prompt as administrator (right click -> run as administrator) in order to access to the USB drive/stick.

That's it, you have done a Virtual Machine disk that should be very tiny (~1KB) and links to your USB drive.

You just need to import this hard drive in VirtualBox and use it as primary hard drive (to boot on) for your new system.

You can do it step by step by following the screenshots:

You can see the result of my Ubuntu 10.10 on my 8GB USB stick running on VirtualBox on Windows 7 at the very beginning of this article (first screenshot).

see Video of this tutorial

============================

http://www.plop.at/en/bootmanagers.html
The Plop Boot Manager is a small program with unbelievable many features.
Here is a list of features, but you can do more...
USB boot without BIOS support (UHCI, OHCI and EHCI)
CD/DVD boot without BIOS support (IDE)
PCMCIA CardBus support to enable boot from USB PC-Cards
Floppy boot
Different profiles for operating systems
Define up to 16 partitions
No extra partition for the boot manager
Hidden boot, maybe you have a rescue system installed and the user should not see that there is another system installed
Boot countdown
Hide partitions
Password protection for the computer and the boot manager setup
Backup of partition table data
Textmode user interface 80x50
Graphical user interface 640x480, 800x600, 1024x786, 1280x1024
MBR partition table edit
Start of the boot manager from harddisk, floppy, USB, CD, DVD
Starting from Windows boot menu
Starting from LILO, GRUB, Syslinux, Isolinux, Pxelinux (network)
It can be used as PCI option ROM in your BIOS
Access the whole USB hard disk (up to 2TB) even when the bios has a 128 GiB limit
You can run the boot manager over the network
Start the networkcard bootrom from the boot manager to boot from the network
Documentation - Download - News


Ubuntu Linux 10.04 LTS live USB flash drive with a Ubuntu ISO image and Oracle Virtual Box

19/06/2010

See how to make a Ubuntu Linux 10.04 LTS live USB flash drive with a Ubuntu ISO image and Oracle Virtual Box. No CD burning or Ubuntu install in Virtual Box is required. This is one of the fastest and most hassle free ways to make a Bootable USB live Flash drive with Ubuntu installed on it.

You need to first make the virtual machine in Oracle Virtual Box and mount your Ubuntu CD or ISO file on your newly created Virtual machine by going into the settings for Virtual Box and setting the CD to your Ubuntu ISO install Live Cd which you download from Ubuntu. Mount your USB thumb drive which has at least 700MB of free space or is 1 GB in size. Also, make sure the USB drive is at least a USB 2.0 drive. If you have a USB 3.0 drive it will be faster, but USB 2.0 is good enough for a Ubuntu live Flash drive. Save your settings, and start Ubuntu from Virtual box.

Wait for Ubuntu to load and pick "Try Ubuntu 10.04 LTS". Once Ubuntu is done loading, you should go to your System then Administration tools and Make Startup Disc creator, and pick your USB thumb drive. Click the "Make start up disc" button.

If you like, you can change the amount of space Ubuntu reserves for storing your personal files like music, docs, videos, etc.

Wait for Ubuntu to finish making your Ubuntu startup USB drive. It should take about 10-20 minutes depending on how fast your computer is and how fast your USB is.

The benefits of installing Ubuntu on a flash drive compared to a CD is it is faster, and quieter, and you can also install programs on your Ubuntu Flash drive and put your files on your drive.

 Create a Bootable USB Flash Drive to Install Ubuntu 11.10 in 2 min========================
http://reboot.pro/topic/8581-boot-your-usb-drive-in-virtualbox/
I am aware of three types of rawdisk-descriptors.
The names are given by the parameter "createType"
"fullDevice" used by VMware
"fullDevice' used by VirtualBox
"partitionedDevice" used by VMware
The examples all describe a 4 Gb kingston USB-stick
"fullDevice" used by VMware:

# Disk DescriptorFile
version=1
encoding="windows-1252"
CID=9e497682
parentCID=ffffffff
createType="fullDevice"
# Extent description
RW 7868416 FLAT "\\.\PhysicalDrive3" 0

# The Disk Data Base 

#DDB
ddb.virtualHWVersion = "7"
ddb.uuid = "60 00 C2 91 f9 42 a4 72-10 10 ca bb ac d1 35 28"
ddb.geometry.cylinders = "489"
ddb.geometry.heads = "255"
ddb.geometry.sectors = "63"
ddb.geometry.biosCylinders = "489"
ddb.geometry.biosHeads = "255"
ddb.geometry.biosSectors = "63"
ddb.adapterType = "lsilogic"

"fullDevice' used by VirtualBox:

# Disk DescriptorFile
version=1
CID=7a174421
parentCID=ffffffff
createType="fullDevice"

# Extent description
RW 7868416 FLAT "\\.\PhysicalDrive3"

# The disk Data Base 

#DDB
ddb.virtualHWVersion = "4"
ddb.adapterType="ide"
ddb.geometry.cylinders="7805"
ddb.geometry.heads="16"
ddb.geometry.sectors="63"
ddb.uuid.image="f005cd99-df1b-4c8d-8f75-1f71f37b4d75"
ddb.uuid.parent="00000000-0000-0000-0000-000000000000"
ddb.uuid.modification="00000000-0000-0000-0000-000000000000"
ddb.uuid.parentmodification="00000000-0000-0000-0000-000000000000"

"partitionedDevice" used by VMware:

# Disk DescriptorFile
version=1
encoding="windows-1252"
CID=bf09c8c4
parentCID=ffffffff
createType="partitionedDevice"

# Extent description
RW 63 FLAT "esx4-1-pt.vmdk" 0
RW 7855785 FLAT "\\.\PhysicalDrive3" 63
RW 12568 ZERO 

# The Disk Data Base 

#DDB
ddb.virtualHWVersion = "7"
ddb.uuid = "60 00 C2 9d 71 10 ee 3e-79 74 69 77 b1 97 70 df"
ddb.geometry.cylinders = "489"
ddb.geometry.heads = "255"
ddb.geometry.sectors = "63"
ddb.geometry.biosCylinders = "489"
ddb.geometry.biosHeads = "255"
ddb.geometry.biosSectors = "63"
ddb.adapterType = "lsilogic"

this type stores a copy of the first 63 sectors in an additional file named *-pt.vmdk"
In the case of the VMware - descriptors ... they can be easily redefined as IDE-disks.
Don't know if this works with virtualbox ? - never tested it.
The uuid-values can be skipped - they are not essential.
------------------

• A "link" is not an image.
• A "descriptor file" is not an image. 
• A "virtual hard disk file" is not an image.

------------------
Added Linux Live USB which uses portable virtualbox . 
Updated tutorial to work with Virtualbox 4.
http://agnipulse.com...-in-virtualbox/
The new vboxmanage command no longer supports the register switch.So you have to manually add the vmdk file to your virtual machine. 
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For LinuxLive USB Creator, I created a launcher for VirtualBox which automatically virtualizes the hard drive (or USB key) it is run from.
My launcher is a derivative work of Portable VirtualBox 
( http://vbox.me) 
and can either runs in Portable Mode or in regular mode if you already have VirtualBox installed on your machine.
You can download it from :

• Here for VirtualBox 4.X

You just have to unzip it to the hard drive you want to Virtualize then run VirtualBox.exe for full interface orVirtualize_this_key.exe to directly run the VM.

/!\ DO NOT USE THIS ON YOUR SYSTEM HARD DRIVE IT MAY CORRUPT IT /!\

How it works
It automatically creates the VMDK file for your hard drive (or USB key). I'm talking about a raw device mapping here, not a clone image.
Launcher then checks if you already have VirtualBox :

• if you do have it, then it runs the regular VirtualBox (no changes are made to your VirtualBox config since it's another one that is loaded)
• if you don't have it, then it runs Portable-VirtualBox

Now you can show Linux (or any other OS) to your friends directly on their computers.
Technical details
I'm using VBOX_USER_HOME environment variable in order to start VirtualBox with another configuration.
To create a Raw Device Mapping, i'm using WMI, which may not work on Windows Home editions (needs confirmation).
Portable version may not have all the features working.
==============================
http://www.pendrivelinux.com/boot-a-usb-flash-drive-in-virtualbox/
http://como-hace.blogspot.com/2011/07/como-hacer-el-usb-bootable-en.html

Clone VDI tool

https://forums.virtualbox.org/viewtopic.php?f=6&t=22422

CloneVDI tool - Discussion & Support

by mpack » 15. Sep 2009, 23:13

Many Windows users dislike the fact that you currently have to use the Command Prompt to clone VDI files (*). Also, questions often arise related to VDI files such as "how do I increase the maximum size of a VDI?" or "how can I make my dynamic VDI file small again?". As a recent vacation project I decided to try to write a nice simple tool that provided a good answer to all of these questions. Hopefully I succeeded.

(*) [edit: VirtualBox v4.1 finally added GUI support for cloning]

Attached to this message is a zip file containing the software tool that I wrote, which I call "CloneVDI" (currently at version 2.10). Features as of this release include:

• Reads VDI,VHD,VMDK,Parallels HDD,RAW files and physical drives, writes VDI.
• A simple GUI Interface.
• A CLI interface too (for people who like that kind of thing!)
• Ability to compact (discard unused blocks from) the clone, with no need to run sdelete/zerofree first.
• Ability to enlarge the maximum size of a virtual disk, optionally enlarging the main partition too.
• Merge snapshot VDI chain into a single VDI (VHD and VMDK snapshot chains supported too).
• User choice to either keep the old UUID or generate a new one for the clone.
• Some useful diagnostics about the source VDI, such as the partition map and the internal fileystem.
• Better feedback while cloning: a progress bar and an estimated time to completion.
• It seems to be significantly faster than "VBoxManage clonehd".
• Open source.

To install, simply create a folder and unpack the zip contents into it. Optionally, you can create a shortcut to link your desktop to the CloneVDI.exe file in the target folder. The zip file includes release notes which hopefully provides answers to all of your questions.

Note that this tool is not simply a GUI front end for VBoxManage. Instead it uses my own code to read and write VDI files (and other formats), and therefore works in a rather different way, with different features and capabilities.

Enjoy. Feel free to ask any questions here, but read the release notes first.

[ Edit: 12th Sep 2012. CloneVDI attachment updated to v2.10. Bugfixes plus support for VMDK and VHD snapshots. ]

Virtual Hard Disk for Native Boot

http://technet.microsoft.com/en-us/library/dd744338(WS.10).aspx 
Applies To: Windows 7, Windows Server 2008 R2

Note
This content applies to Windows 7. For Windows 8 content, see Windows Deployment with the Windows ADK.

This walkthrough describes how to create and configure a virtual hard disk (VHD) running Windows® 7 for native boot. A native-boot VHD is a virtual hard disk that can be used as the running operating system on designated hardware without any other parent operating system. This is in contrast to a scenario where a VHD is connected to a virtual machine on a computer with a parent operating system.
In this release, VHDs can be applied to computers that have no other installations of Windows, for usage as a native-boot VHD, without a virtual machine or hypervisor. (A hypervisor is a layer of software below the operating system that runs virtual computers.) This allows for greater flexibility in workload distribution in that a single set of tools can be used to manage images for virtual machines and designated hardware.

Note
This walkthrough describes how to deploy the VHD to a computer with no other installations of Windows. For more information about deploying multiple VHDs with native-boot on a single computer, or deploying VHDs on computers with a parent operating system, see Add a Native-Boot Virtual Hard Disk to the Boot Menu.

Prerequisites

To complete this walkthrough, you need the following:

• A technician computer running Windows 7. A technician computer is any computer with the Windows OEM Preinstallation Kit (Windows OPK) or Windows Automated Installation Kit (Windows AIK) tools installed on it.
• A Windows 7 image (.wim) file. For more information, see Capture and Apply Windows Images.
  

  Note
  Use a generalized Windows 7 image. A specialized image is customized to a specific computer, while a generalized image can be deployed across many computers. For more information about the specialize and generalize configuration passes, see Windows Setup Configuration Passes.

• A Windows 7 Windows PE disk. For more information, see Walkthrough: Boot Windows PE from CD-ROM.
• A destination computer on which to install the VHD. This computer requires 30 gigabytes (GB) or more of free disk space. You can install the VHD to a computer already running other operating system installations, or as the only operating system on a computer.

For more information about using VHDs in an enterprise environment, see Understanding Virtual Hard Disks with Native Boot.

Step 1: Create a VHD

1. On the technician computer, use the Diskpart tool to create, attach, partition, and format a new virtual hard disk. You can attach a VHD by using the Attach vdisk command which adds the .vhd file as a disk to the storage controller on the host. This virtual disk will appear as the V: drive at the end of this procedure. The Detach command will stop this virtual disk from appearing on the host.
   In this example, you create a 25 GB fixed-type VHD. For more information about VHD image types, see Understanding Virtual Hard Disks with Native Boot. For more information about the DiskPart tool, see this Microsoft Web site.
   At a command prompt, type:
   
   diskpart
   create vdisk file=c:\windows7.vhd maximum=25600 type=fixed
   select vdisk file=c:\windows7.vhd
   attach vdisk
   create partition primary
   assign letter=v
   format quick label=vhd
   exit
   

Step 2: Apply a Windows 7 image

1. Use ImageX to apply the .wim file to the primary partition of the VHD. At a command prompt, type:
   
   cd /d "c:\program files\\tools\\"
   imagex /apply  1 v:\
   

   Where is Windows OPK or Windows AIK and is x86, amd64 or ia64.
2. Use the DiskPart tool to detach the virtual disk after applying the image. At a command prompt, type:
   
   diskpart
   select vdisk file=c:\windows7.vhd
   detach vdisk
   exit
   

3. Copy the VHD file to a network share or USB hard drive. For example,
   
   net use n: \\server\share\
   md N:\VHDscopy c:\windows7.vhd n:\VHDs\
   

Step 3: Clean and partition the destination computer

1. Boot the destination computer with your bootable Windows PE media.
2. Clean the hard disk using the DiskPart tool.
   

   Caution
   Running this command will erase all information on the computer. If you are deploying a VHD and want to maintain an existing native-boot VHD deployment or running operating system on the destination computer, do not run this command. See Add a Native-Boot Virtual Hard Disk to the Boot Menu for more information.

   At a command prompt, type:
   
   diskpart
   select disk 0
   clean
   

3. Create a system partition. This example uses a 300 megabyte (MB) system partition. At a command prompt, type:
   
   create partition primary size=300
   format quick fs=ntfs
   assign letter=s
   active
   

4. Create a primary partition. In this example the primary partition is given the remaining disk space. At a command prompt, type:
   
   create partition primary
   format quick fs=ntfs
   assign letter=c
   exit
   

Step 4: Deploy the VHD with native-boot capabilities

1. Copy the VHD file to the destination computer. At a command prompt, type:
   
   copy N:\VHDs\Windows7.vhd c:
   

2. Use the DiskPart tool to attach the VHD on the destination computer. At a command prompt, type:
   
   diskpart
   select vdisk file=c:\windows7.vhd
   attach vdisk
   
   

3. The VHD is assigned a volume letter when it is attached. Find the letter associated with the VHD in the volume list and then exit the DiskPart tool. At a command prompt, type:
   
   list volumeselect volume assign letter=vexit
   

4. Use the BCDboot tool, located in the \System32 directory of the Windows 7 VHD or in a Windows® 7 Windows PE media, to copy the boot-environment files from the \Windows directory in the VHD to the system partition. The BCDboot tool will create the BCD configuration to boot from the VHD. For more information about the BCDboot tool, see BCDboot Command-Line Options.
   For example, at a command prompt, type:
   
   cd v:\windows\system32
   bcdboot v:\windows /s s:
   

5. Use the DiskPart tool to detach the virtual disk. At a command prompt, type:
   
   diskpart
   select vdisk file=c:\windows7.vhd
   detach vdisk
   exit
   

6. Restart the destination computer.
   The Windows 7 Boot Manager will boot the Windows 7 operating system image contained in the .vhd file.

Next Steps

To deploy a second VHD with native-boot capabilities to the same computer, you can copy the file and add it to the existing BCDboot menu using the BCDedit tool. For more information, see Add a Native-Boot Virtual Hard Disk to the Boot Menu.
Concepts

Understanding Virtual Hard Disks with Native Boot
Add a Native-Boot Virtual Hard Disk to the Boot Menu

http://en.wikipedia.org/wiki/VHD_(file_format)

Virtual Hard Disk

Filename extension	.vhd
Developed by	Connectix / Microsoft
Type of format	Virtual machine disk image

VHD (Virtual Hard Disk) is a file format which represents a virtual hard disk drive (HDD). It may contain what is found on a physical HDD, such as disk partitions and a file system, which in turn can contain files and folders. It is typically used as the hard disk of a virtual machine.
The format was created by Connectix for Connectix Virtual PC product, which was later acquired by Microsoft in 2003, for what is now known as Microsoft Virtual PC.
Since June 2005, Microsoft has made the VHD Image Format Specification available to third parties under the Microsoft Open Specification Promise.^[1]

1 Features 1.1 Supported formats 1.2 Advantages 1.3 Native VHD Boot 1.4 Limitations 2 Software support 2.1 Offline modification 3 Virtual Floppy Disk (VFD) 4 See also 5 References

Disk image file formats
Optical discs	CCD/IMG/SUB CUE/BIN CSO DAA IBP/IBQ ISO ISZ MDS/MDF MDX NRG UIF
Hard disks	DMG ISO QCOW UDIF VDI VHD VMDK WIM
Floppy disks	ADF/ADZ DCF DMS IMA/IMZ IMG VFD
Flash drives	ISO
CD-DA	Disc Description Protocol