I had some issues this morning with an EC2 instance so I stopped it and changed it's type and it seemed to unmount one of my drives.
Now, I can't mount anything, including freshly created, attached and formatted drives.
I keep getting the same error:
mount: Stale NFS file handle
I don't even think I'm using NFS ...
Any ideas on how to solve this?
Update & Resolution
Added my own answer below.