osx question: Is it possible to mount an external hard drive whilst in safe boot mode? If so, how?
So you need to use:
The actual device might be something else then disk1s1, depending on the external drive, and you might have to create the directory BackupDrive, or use something else that's available in /Volumes.
to get a list of devices, your external drive should be there. I think it should be something like disk1s1, or something that looks like it.
Hope this helps.