This command creates a new virtual hard disk image. The syntax is as follows:
VBoxManage createhd --filename <filename> --size <megabytes> [--format VDI|VMDK|VHD] (default: VDI) [--variant Standard,Fixed,Split2G,Stream,ESX]
where the parameters mean:
--filename
Allows to choose a file name. Mandatory.
--size
Allows to define the image capacity, in 1 MiB units. Mandatory.
--format
Allows to choose a file format for the output file different from the file format of the input file.
--variant
Allows to choose a file format variant for the output file. It is a comma-separated list of variant flags. Not all combinations are supported, and specifying inconsistent flags will result in an error message.
For compatibility with earlier versions of VirtualBox, the "createvdi" command is also supported and mapped internally to the "createhd" command.