Debian also has aufs

Also a minor nit for the article. It says the only differences between files are saved. This is not correct. Only the modified files are saved would be more correct. AUFS OverlayFS and unionmounts are namespace unification file systems. They just unify the name space not the data in the files itself. So a 1 byte change to a 400 meg file will cause the 400 meg file to be copied up to the r/w branch.