Sun Microsystems VIRTUALBOX VERSION 3.1.0_BETA2 - Manual (Page 147)

9 Advanced topics
As you can see, the command is identical to the one for “full hard disk” access,
except for the additional -partitions parameter. This example would create the
image /path/to/file.vmdk (which, again, must be absolute), and partitions 1
and 5 of /dev/sda would be made accessible to the guest.
VirtualBox uses the same partition numbering as your Linux host. As a result, the
numbers given in the above example would refer to the first primary partition and the
first logical drive in the extended partition, respectively.
On a Windows host, instead of the above device specification, use e.g.
\\.\PhysicalDrive0 . On a Mac OS X host, instead of the above device speci-
fication use e.g. /dev/disk1. Note that on OS X you can only use partitions which
are not mounted (eject the respective volume first). Partition numbers are the same
on Linux, Windows and Mac OS X hosts.
The numbers for the list of partitions can be taken from the output of
VBoxManage internalcommands listpartitions -rawdisk /dev/sda
The output lists the partition types and sizes to give the user enough information to
identify the partitions necessary for the guest.
Images which give access to individual partitions are specific to a particular host
disk setup. You cannot transfer these images to another host; also, whenever the host
partitioning changes, the image must be recreated.
Creating the image requires read/write access for the given device. Read/write
access is also later needed when using the image from a virtual machine. If this is not
feasible, there is a special variant for raw partition access (currently only available on
Linux hosts) that avoids having to give the current user access to the entire disk. To
set up such an image, use
VBoxManage internalcommands createrawvmdk -filename /path/to/file.vmdk
-rawdisk /dev/sda -partitions 1,5 -relative
When used from a virtual machine, the image will then refer not to the entire disk, but
only to the individual partitions (in the example /dev/sda1 and /dev/sda5). As a
consequence, read/write access is only required for the affected partitions, not for the
entire disk. During creation however, read-only access to the entire disk is required to
obtain the partitioning information.
In some configurations it may be necessary to change the MBR code of the created
image, e.g. to replace the Linux boot loader that is used on the host by another boot
loader. This allows e.g. the guest to boot directly to Windows, while the host boots
Linux from the “same” disk. For this purpose the -mbr parameter is provided. It
specifies a file name from which to take the MBR code. The partition table is not
modified at all, so a MBR file from a system with totally different partitioning can be
used. An example of this is
VBoxManage internalcommands createrawvmdk -filename /path/to/file.vmdk
-rawdisk /dev/sda -partitions 1,5 -mbr winxp.mbr
The modified MBR will be stored inside the image, not on the host disk.
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