@Steve - only time i've seen the cmd line not work is if you've punched it in and have /Volumes/MBED mounted (no media attached). You should have physical media as MBED 2,3 etc... if this is the case. A simple ls /Volumes/ with mbed attached should show you the mounted volumes
@sam - I can't figure out what you are trying to suggest.
What did you mean by "punched it in?" Punch what in? Punch what into what? I haven't punched anything in since I punched paper tape bootloaders for minicomputers in the 80's. That can't be what you mean.
The following sounds like a contradiction:
and have /Volumes/MBED mounted (no media attached).
I would think "No media attached" means "not mounted?"
I've been hacking UNIX since the 80's (ported it to new hardware.) I use Macs these days because they are now UNIX based. Using "ls" in bash to see what is mounted is routine. I also see the MBED or BOOTLOADER icon on the desktop when they are mounted so using 'ls' in bash is redundant.
My environment is on the newest release of OSX Yosemite (10.10). Whenever I try to mount the my FRDM-KL25Z micro-controller, my instance of OSX can only mount the drive in read-only mode. This prohibits me from copying my programs over to the mounted mbed volume that is visible to my computer.
Other additional information to note: I've tested this on several of my friends' computers running OSX Mavericks (10.9), and the ability to copy programs on the mounted drive works fine there.