Aufs included in Ubuntu kernels is broken, what a surprise. In addition it has been dropped from newer kernels with claims that overlayfs does exactly same thing. It doesn't and everyone knows it except that one developer who decided it does and can't admit he made mistake. It seems aufs (and overlayfs) in Ubuntu is not really supposed to be used but only be part of install process. If so you guys shouldn't include it outside installer.. WontFix you too.