Transfer files from the host OS to the virtual drive

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Many users prefer to test ReactOS under emulators and virtualization software like QEMU or VMware, but for testing their software they will need to copy their files into the .iso images and add them into proper directories which can become a difficult job. A way around this is to mount the virtual hard drives as disk drives attached to the system itself.

In Windows

ImDisk Virtual Disk Driver

Web Site

ImDisk is a virtual disk driver for Windows NT/2000/XP/2003/Vista/2008. It can use one or more disk image files to create virtual hard disk, floppy or CD/DVD drives .The install package installs a console-mode control program called imdisk.exe and a Control Panel applet. After install is finished, type imdisk without parameters for syntax help or double click the ImDisk icon in the Control Panel. It also adds a menu item in Windows Explorer so that you can right-click on a file to mount it as a virtual disk drive. Users of mdconfig in FreeBSD will probably be familiar with the command line syntax of imdisk.exe. The driver, service and control program can be uninstalled using the Add/Remove programs applet in the Control Panel. No reboot is required for installing or uninstalling.

The install package also contains a user-mode helper service that enables the virtual disk driver to forward I/O requests to other computers on the network. This makes it possible to boot a machine with NTFS partitions with a *nix Live-CD and use the included devio tool to let ImDisk on another computer running Windows on the network mount the NTFS partition on the machine you booted with the *nix Live-CD. This way you can recover information and even run chkdsk on drives on machines where Windows does not boot.

ImDisk Virtual Disk Driver

imdisk -a -t type -m mountpoint [-n] [-o opt1[,opt2 ...]] [-f|-F file]

      [-s size] [-b offset] [-S sectorsize] [-u unit] [-x sectors/track]
      [-y tracks/cylinder] [-p "format-parameters"]

imdisk -d [-u unit | -m mountpoint] imdisk -l [-u unit | -m mountpoint] imdisk -e [-s size] [-o opt1[,opt2 ...]] [-u unit | -m mountpoint]

-a Attach a virtual disk. This will configure and attach a virtual disk

       with the parameters specified and attach it to the system.

-d Detach a virtual disk from the system and release all resources.

-e Edit an existing virtual disk.

       Along with the -s parameter extends the size of an existing virtual
       disk. Note that even if the disk can be extended successfully, the
       existing filesystem on it can only be extended to fill the new size
       without re-formatting if you are running Windows 2000 or later and the
       current filesystem is NTFS.
       Along with the -o parameter changes media characteristics for an
       existing virtual disk. Options that can be changed on existing virtual
       disks are those specifying wether or not the media of the virtual disk
       should be writable and/or removable.

-t type

       Select the backingstore for the virtual disk.

vm Storage for this type of virtual disk is allocated from virtual memory

       in the system process. If a file is specified with -f that file is
       is loaded into the memory allocated for the disk image.

file A file specified with -f file becomes the backingstore for this

       virtual disk.

proxy The actual backingstore for this type of virtual disk is controlled by

       an ImDisk storage server accessed by the driver on this machine by
       sending storage I/O request through a named pipe specified with -f.

-f file or -F file

       Filename to use as backingstore for the file type virtual disk, to
       initialize a vm type virtual disk or name of a named pipe for I/O
       client/server communication for proxy type virtual disks. For proxy
       type virtual disks "file" may be a COM port or a remote server
       address if the -o options includes "ip" or "comm".
       Instead of using -f to specify 'DOS-style' paths, such as
       C:\dir\image.bin or \\server\share\image.bin, you can use -F to
       specify 'NT-style' native paths, such as
       \Device\Harddisk0\Partition1\image.bin. This makes it possible to
       specify files on disks or communication devices that currently have no
       drive letters assigned.

-l List configured devices. If given with -u or -m, display details about

       that particular device.

-n When printing ImDisk device names, print only the unit number without

       the \Device\ImDisk prefix.

-s size

       Size of the virtual disk. Size is number of bytes unless suffixed with
       a b, k, m, g, t, K, M, G or T which denotes number of 512-byte blocks,
       thousand bytes, million bytes, billion bytes, trillion bytes,
       kilobytes, megabytes, gigabytes and terabytes respectively. The suffix
       can also be % to indicate percentage of free physical memory which
       could be useful when creating vm type virtual disks. It is optional to
       specify a size unless the file to use for a file type virtual disk does
       not already exist or when a vm type virtual disk is created without
       specifying an initialization image file using the -f or -F. If size is
       specified when creating a file type virtual disk, the size of the file
       used as backingstore for the virtual disk is adjusted to the new size
       specified with this size option.
       The size can be a negative value to indicate the size of free physical
       memory minus this size. If you e.g. type -400M the size of the virtual
       disk will be the amount of free physical memory minus 400 MB.

-b offset

       Specifies an offset in an image file where the virtual disk begins. All
       offsets of I/O operations on the virtual disk will be relative to this
       offset. This parameter is particularily useful when mounting a specific
       partition in an image file that contains an image of a complete hard
       disk, not just one partition. This parameter has no effect when
       creating a blank vm type virtual disk. When creating a vm type virtual
       disk with a pre-load image file specified with -f or -F paramters, the
       -b parameter specifies an offset in the image file where the image to
       be loaded into the vm type virtual disk begins.

-S sectorsize

       Sectorsize to use for the virtual disk device. Default value is 512
       bytes except for CD-ROM/DVD-ROM style devices where 2048 bytes is used
       by default.

-x sectors/track

       See the description of the -y option below.

-y tracks/cylinder

       The -x and -y options can be used to specify a synthetic geometry.
       This is useful for constructing bootable images for later download to
       physical devices. Default values depends on the device-type specified
       with the -o option. If the 'fd' option is specified the default values
       are based on the virtual disk size, e.g. a 1440K image gets 2
       tracks/cylinder and 18 sectors/track.

-p "format-parameters"

       If -p is specified the 'format' command is invoked to create a
       filesystem when the new virtual disk has been created.
       "format-parameters" must be a parameter string enclosed within
       double-quotes. The string is added to the command line that starts
       'format'. You usually specify something like "/fs:ntfs /q /y", that
       is, create an NTFS filesystem with quick formatting and without user

-o option

       Set or reset options.

ro Creates a read-only virtual disk. For vm type virtual disks, this

       option can only be used if the -f option is also specified.

rw Specifies that the virtual disk should be read/writable. This is the

       default setting. It can be used with the -e parameter to set an
       existing read-only virtual disk writable.

rem Specifies that the device should be created with removable media

       characteristics. This changes the device properties returned by the
       driver to the system. For example, this changes how some filesystems
       cache write operations.

fix Specifies that the media characteristics of the virtual disk should be

       fixed media, as opposed to removable media specified with the rem
       option. Fixed media is the default setting. The fix option can be used
       with the -e parameter to set an existing removable virtual disk as
       Note that virtual floppy or CD/DVD-ROM drives are always read-only and
       removable devices and that can not be changed.

cd Creates a virtual CD-ROM/DVD-ROM. This is the default if the file

       name specified with the -f option ends with either .iso or .bin

fd Creates a virtual floppy disk. This is the default if the size of the

       virtual disk is any of 160K, 180K, 320K, 360K, 640K, 720K, 820K, 1200K,
       1440K, 1680K, 1722K, 2880K, 123264K or 234752K.

hd Creates a virtual fixed disk partition. This is the default unless

       file extension or size match the criterias for defaulting to the cd or
       fd options.

ip Can only be used with proxy-type virtual disks. With this option, the

       user-mode service component is initialized to connect to an ImDisk
       storage server using TCP/IP. With this option, the -f switch specifies
       the remote host optionally followed by a colon and a port number to
       connect to.

comm Can only be used with proxy-type virtual disks. With this option, the

       user-mode service component is initialized to connect to an ImDisk
       storage server through a COM port. With this option, the -f switch
       specifies the COM port to connect to, optionally followed by a colon,
       a space, and then a device settings string with the same syntax as the
       MODE command.

-u unit

       Along with -a, request a specific unit number for the ImDisk device
       instead of automatic allocation. Along with -d or -l specifies the
       unit number of the virtual disk to remove or query.

-m mountpoint

       Specifies a drive letter or mount point for the new virtual disk, the
       virtual disk to query or the virtual disk to remove. When creating a
       new virtual disk you can specify #: as mountpoint in which case the
       first unused drive letter is automatically used.

VMware Disk Mount

  • VMware Disk Mount Utility is easier to use but will work only with .vmdk files.(Official VMware virtual disk file format.)
  • Download and install the tool which is available at the VMware website.
  • Start Command Prompt.
  • Move to the installation directory (e.g. C:\Program Files\VMware\VMware DiskMount Utility\)
  • Mounting the virtual drive.

Issue the following command,

vmware-mount z: C:\ReactOS\ReactOS.vmdk

What it does,

vmware-mount - Starts the mount application.
z:           - Drive letter for the mounted drive. (You can use any free drive letter.)
...(Path)    - Path to the virtual disk drive. 
NOTE:  - The path above is an example. Use the path where you have saved your .vmdk file.

Unmounting the virtual drive

To unmount the virtual drive issue the following command,

vmware-mount z: /d

What it does,

vmware-mount - Starts the mount application.
z:           - Drive letter for the virtual drive to be unmounted.
/d           - Unmounts the drive.
  • More information on other options can be found in the VMware mount documentation.


  • VDK (Virtual Disk Driver) can mount vmdk and raw format virtual drives which are supported by QEMU and VMware.

Getting the driver (VDK)

You can download VDK from here (x64 here). At the time of writing of this HOWTO the latest version is version 3.2. Download the .zip file and extract it to your desired folder using your favourite archiver.

Setup the driver

  • Open the command prompt and move to the folder where you have extracted VDK using cd command (e.g. C:\VDK).
  • Issue the following command with the command prompt in the same directory,
vdk install /auto

/AUTO Configures the driver to start at the system startup (Note: this option does not start the driver after installation is completed). By default the driver has to be started manually.

The Virtual Disk kernel-mode Driver (vdk.sys) is copied to %SYSTEMROOT%\system32, you may need administrator privileges to install the driver.

Start the Driver

Even though the driver is installed, it may not be actually running. To start it issue the following command,

vdk start

If the driver is not already installed, this command attempts to install it with the default options. It is recommended that you use vdk install /auto so that you do not have to manually start the driver every time.

Mounting the virtual drive


 VDK.EXE OPEN disk# image [/RW | /WB | /UNDO] [/P:part#] [/L:drive]


 disk#     Specifies the virtual disk number. This must be the first parameter. '*' means the first available disk, and if all existing disk is busy a new virtual disk is created.
 image     Specifies the path to the disk image file. This must be the second parameter.
 /RW       Open the image in Read-Write mode.
 /WB       Open the image in Write-Block mode.
 /UNDO     Creates a REDO log for the image and open in Read-Write mode.
 /P:part#  Specifies a partition number to set a drive letter. Drive letters can be set/removed later with LINK/ULINK commands. By default, drive letters are assigned to all mountable partitions.
 /L:drive  Specifies drive letters to assign to partitions.By default, the first available drive letter is used.

Only one of /RW, /WB and /UNDO can be used at a time. When none of these is specified, the image is opened in Read-Only mode.

  • Example of Vdk usage

In the vdk directory issue the following command,

vdk open * C:\ReactOS\ReactOS.vmdk /rw

Unmounting the virtual drive

Once you are done using the virtual drive it needs to be unmounted. This is done by issuing the following command,

vdk close * 

Failure to do this will result in the drive being locked and usable to VMware or QEMU.

Stopping the driver

If you want you can stop the driver using,

vdk stop

More details and options are available in the Readme.txt in the previously downloaded .zip file.


Mounting a QEMU image

Most Linux distributions allow you to mount virtual disk images using the mount command. Ubuntu is used in this example, but it should work in most distributions.

For most of these actions you will need root access, so use the sudo command. You will need to enter a password for this. First you need to create a mounting directory,

sudo mkdir /media/ReactOS

Then, make sure your virtual image file is in RAW format. I created my image in QEMU Launcher, where you can select this format. If your image is in QCOW format, you can use the following command to convert to RAW,

qemu-img convert <image-file> -O raw <image-file.raw>

After this is done, you can mount the image,

sudo mount -o loop,offset=32256 <image-file> /media/ReactOS -t vfat

When you are done using the image file, you can unmount it easily by using,

sudo umount /media/ReactOS