打开虚拟机提示如下信息：

"Failed to open virtual machine located in /media/mint/home/xxx/VirtualBox VMs/file2/xxx.vbox. A differencing image of snapshot {xxxxxxxxxxxxxx} could not be found. Could not find an open hard disk with UUID {xxxxxxxxxxxxxxxxxxxx}. "

修复步骤：

1. 备份vbox文件： yourVirtualMachine.vbox.
2. 编辑vbox文件：yourVirtualMachine.vbox.
3. 在 .vbox 文件中查找丢失的 UUID e.g. 36bbf5bd-3a5e-48ab-80d6-6a2952788fdc.

4. 可以找到如下面的代码片段:

   <AttachedDevice type="HardDisk" hotpluggable="true" port="0" device="0">
     <Image uuid="{36bbf5bd-3a5e-48ab-80d6-6a2952788fdc}"/>
   </AttachedDevice>
   

5. 删除整个AttachedDevice代码片段.

6. 保存编辑的文件.
7. 启动VirtualBox, 重新add或者import vbox文件.
8. 编辑 imported VM.
9. 打开 "storage" 面板.
10. 添加新的 hard disk ( existing VM file e.g. vdi, vmdk) to IDE- or SATA-Controller.