Resize hdd image

/usr/local/bin/VBoxManage modifyhd /mnt/main/VM/machine-img/win7/win7.vdi --resize 30480

Suspend virtual machine
su vboxuser -c "/usr/local/bin/VBoxManage controlvm w7 savestate"
Resume virtual machine
su vboxuser -c "/usr/local/bin/VBoxManage startvm --type headless w7"