Vboxmanage/compact

Compact VirtualBox's VDI file size

Reduce vdi file size size

Steps

1. Run defrag in the guest (Windows only)
2. Nullify free space:

Linux Guest

dd if=/dev/zero of=/var/tmp/bigemptyfile bs=4096k
rm /var/tmp/bigemptyfile 

or

telinit 1 
mount -o remount,ro /dev/sda1 zerofree -v /dev/sda1 

Windows Guest

1. download SDelete from Sysinternals
2. and run this:

sdelete.exe c: -z 

replace C: with the drive letter of the VDI

1. Shutdown the guest VM

1. Now run VBoxManage's modifymedium command with the --compact option:

Linux Host

vboxmanage modifymedium --compact /path/to/thedisk.vdi 

Windows Host

VBoxManage.exe modifymedium --compact c:\path\to\thedisk.vdi 

Mac Host

VBoxManage modifymedium --compact /path/to/thedisk.vdi 
VBoxManage is located here: /Applications/VirtualBox.app/Contents/MacOS/VBoxManage

Anwendung

# vboxmanage modifymedium --compact windows10.vdi
0%...10%...20%...30%...40%...50%...60%...70%...80%...90%...100%