Shrink Virtualbox VM VDI File Size

Virtualbox  的VM image size (.vdi file)有时候会变得很大， 如何缩减文件大小呢？ 

这里我的host = MacBook Pro, guest = Win7. 虚拟机创建的时候设置的是 “Dynamically Expanding Storage” , 但以后随着增删文件操作而磁盘只会增加不会减少。

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 c:
   

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:\path\to\thedisk.vdi --compact
   

   With a Mac Host run this:

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

This reduces the vdi size.