Verify Original Disk While Booted from Sandbox?
 

Hope this isn't too far off topic.

When I'm booted from my sandbox partition and want to use Disk Utility to verify volumes, I can verify the sandbox partition which is the startup disk. I cannot verify the original partition on which the sandbox is based. It says "Verify volume failed with error Could not unmount disk". Makes sense.

Is there a way to get Disk Utility to check the original like it checks the sandbox--by not trying to unmount the original? (Of course, I'm looking to avoid booting from the original partition just to do this.)

No, you can't do that: a sandbox shares your user files, so the original volume will still be busy.

What you should do instead is start up from your OSX install disc and run Disk Utility from the Installer or Utilities menu (depending on the version of the disc you have).