10/06/06 00:35:23 SP1ps5jc0
Usermanual.pdfの146ページより
8.18 VBoxManage modifyhd
In addition, the modifyhd --compact command can be used to compact disk images,
i.e. remove blocks that only contains zeroes. For this operation to be effective,
it is required to zero out free space in the guest system using a suitable software tool.
Microsoft provides the sdelete tool for Windows guests. Execute sdelete -c in the
guest to zero the free disk space before compressing the virtual disk image.
VBoxManage modifyhd <uuid>|<filename> [--type normal|writethrough|immutable] [--autoreset on|off] [--compact]
SDelete
URLﾘﾝｸ(technet.microsoft.com)