Scott S Nelson

Takes me forever to find this StackExchange post every time I need it, so I’m copying it here for ease of reference:

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

   With a Linux Guest run this:

   sudo dd if=/dev/zero of=/bigemptyfile bs=4096k
   sudo rm -rf /bigemptyfile
   

   With a Windows Guest, download SDelete from Sysinternals and run this:

   sdelete –z
   

3. Shutdown the guest VM
4. Now run VBoxManage’s modifyhd command with the --compact option:

   With a Linux Host run this:

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

   With a Windows Host run this:

   VBoxManage.exe modifyhd c:pathtothedisk.vdi --compact
   

   With a Mac Host run this:

   VBoxManage modifyhd /path/to/thedisk.vdi --compact
   

This reduces the vdi size.

© Scott S. Nelson