A bug on the Steam version for Linux has a complication with the rm (remove command) on the BASH (Born Again Shell) that will remove everything from your root directory on.
On Valves GitHub Steam for Linux page there are complaints about serious bug that has the potential to wipe out every single personal file on your Linux PC. It will also wipe out documents on USB connected drives, ouch.
The main problem if you are running Steam on Linux is to be careful of their program. It would be wise, not to connect to any local external hard drives while youre running Steam. Users complaining of this bug appear to have moved their .steam or ~/.local/share/steam directories, or invoked Steams Bash script with the reset option enabled.
UPDATE: Valve gave us the following statement: So far we have had a handful of users report this issue, after they manually moved their Steam install. We have not been able to reproduce the reported issue, but we are adding some additional checks to ensure this is not possible while we continue to investigate. If anyone else has experienced this or has more information, they should email firstname.lastname@example.org.
The bug appears to be caused by a line in the Steam.sh Bash script:
rm -rf $STEAMROOT/*.