If you move the Steam home directory of $STEAMROOT in Linux then you are running the risk of running rm -rf on your user directory, which in the case of this unfortunate person on Slashdot included their attached USB hard drive.  This is rather nasty bug and one which is easily avoidable by the use of proper syntax but unfortunately the command rm -rf "$STEAMROOT/"* contains an unnecessary / and without an error checking facility included if there is no $STEAMROOT directory the command run is rm -rf "/"*.  As it is in your home folder you do not even need to be running as root so for the time being it would be very wise to leave your Steam files in their default location and to realize that anything plugged into your machine is not a true backup until removed from your system.

"I launched steam. It did not launch, it offered to let me browse, and still could not find it when I pointed to the new location. Steam crashed. I restarted it. It re-installed itself and everything looked great. Until I looked and saw that steam had apparently deleted everything owned by my user recursively from the root directory. Including my 3tb external drive I back everything up to that was mounted under /media."

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