AFAIK with aufs when a file is touched (ie. only it's metadata changed, not it's contents), then the copy-on-write mechanism of the file system will copy the whole file into the r/w layer, essentially duplicating the file.
Say, I only want to change the metadata (modification time, permissions, owner, etc.) of a lot of files, is there some union-type file system (OverlayFS perhaps?) that only keeps track of the metadata changes, unless the file content is altered - resulting in much less duplication?
Or maybe some other trick can lead to the desired result?
