vbox tricks

Compacting your vbox virtual disk image

1. Open terminal inside your virtual machine and run:  
   sudo dd if=/dev/zero of=EMPTY bs=1M
   sudo rm ./EMPTY

  This will zeroify all the empty blocks on your disk.

2. Shutdown you virtual box.

3. Check what type of virtual drive do you have: VMDK or VDI. VirtualBox shrinking works only with VDI files. 
   If you have a VDI file, proceed to the last step, otherwise you'll need to perform  an additional step of converting your VMDK file 
   to VDI format, using qemu as follows.
Install qemu by typing in mac terminal:  sudo port install qemu
Convert your disk file to raw format:    /opt/local/bin/qemu-img convert <path-to-your-virtual-disk-file.vmdk> <path-to-output.raw>
Convert your disk from raw to vdi: /Applications/VirtualBox.app/Contents/MacOS/VBoxManage convertfromraw <path-to-output.raw> <path-to-your-new-virtual-disk-file.vdi>

3. Open your mac terminal and type: 
    /Applications/VirtualBox.app/Contents/MacOS/VBoxManage modifyhd <path-to-your-virtual-disk-file.vdi> --compact