Originally Posted by vayu
Where is the data from one install when the other install is mounting its partition?
it's temporarily hidden. Once a directory is used as a mountpoint for something else, its original contents is simply ignored. Nothing happens to it, it's just inaccessible while something else is mounted on that directory.
That's nothing to be scared of, though it might be worrying for a moment when the contents of a directory seems to be gone. It's just like you can't see the painting on the wall when you place a wardrobe in front of it.
No problem, keep calm. Everything is fine. ;-)
[X] Doc CPU