安装Compact VirtualBox VM .vdi Disk Size

NOTE: This process only works on dynamically allocated virtual disks. If you're not sure, launch VirtualBox and go to File > Virtual Media Manager. Select the virtual drive and view the properties

Create backups of virtual disks before attempting these steps

Compacting Windows Guest VM

Launch the Windows VM
Inside the VM, launch a web browser and download the sdelete utility Download
Extract the downloaded sdelete .zip file
Copy sdelete.exe for 32-bit OS or sdelete64.exe for 64-bit OS to the C:\Windows directory
Launch Command Prompt by right clicking the Start button > Run > type cmd > Press Enter
Run the following command to zero out the free space on the disk, replace the drive letter to target additional drives
sdelete64.exe c: -z
Once the process completes, shutdown the VM

Compacting Linux Guest VM

Download the SystemRescue live disc Download
Launch VirtualBox Manager
Right click the VM to be compacted > Settings
Select Storage on the left hand side
Select the optical disc drive
Click the disk selection icon > Choose a disk file...
Navigate to the downloaded SystemRescue .iso file
Click Open and OK to close the settings
Right click the VM > Start > Normal Start
Press Enter to boot SystemRescue using default options
Once SystemRescue has finished booting, run the following commands
# list the attached disks
fdisk -l
# find the disk to be compacted
# usually listed as /dev/mapper/....
# run the following, replacing the drive identifier as needed
zerofree -v /dev/mapper/
# after zerofree completes, shutdown the VM
shutdown now
Go back into the VM settings and remove the attached SystemRescue .iso

Compacting the Virtual Disk

Launch VirtualBox Manager on the host device
Right click the VM to be compacted > Show in Explorer
Right click in the white space > Open PowerShell window here...
Run the following command, replacing the file name of the virtual disk
"%programfiles%\Oracle\VirtualBox\vboxmanage.exe" modifymedium disk "name_of_disk.vdi" --compact