./156: `VBoxManage modifyhd compact`

8.13. VBoxManage modifyhd

With the modifyhd command, you can change the type of an existing image between the normal, write-through and immutable modes; see Section 5.2, “Disk image files (VDI, VMDK, VHD)” for details.

Note
For compatibility with earlier versions of VirtualBox, the "modifyvdi" command is also supported and mapped internally to the "modifyhd" command.
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

Mais peut-être que ce n'est pas que ça, le "shrinking" dont tu parles (il y a peut-être aussi des capacités plus génériques de modification de la taille de la partition après installation) ?


Ah, et Virtualbox semble supporter les disques non persistants, cf. la section 5.2 de l'aide.