I'm running into the same issue as @luke101 when I attempt to mount Macintosh HD in my 15" MBP (Late 2014). I've been unable to mount the drive to continue with the procedure.
Any guidance on how I might work around this?
I've tried all of the suggestions regarding " ", , _, and others to try to identify the name of the drive, but the issue still seems to exist because of the space between "Macintosh" & "HD".
Any help would be appreciated, and until I get this figured out my MBP is essentially a brick...that works great on Windows 10 on Bootcamp :(