These 2 directories (/usr/lib/X11 and /usr/X11R6/lib/X11) seems to me an exact copy of each other. I could not find any link between them. Can I rm --force --recursive --verbose /usr/lib/X11 ? And if not, why ? What are the possible explanations that I have 2 copies of the same directory ? Are there any other files or directories that are duplicated somewhere else on my system ?