There is a standard: http://news.stanford.edu/pr/2015/pr-worms-digest-plastics-092915.html http://news.stanford.edu/pr/2015/pr-worms-digest-plastics-09.... Thi

There is a standard: http://news.stanford.edu/pr/2015/pr-worms-digest-plastics-092915.html http://news.stanford.edu/pr/2015/pr-worms-digest-plastics-09.... This is from RedHat. Not implemented by everyone, but modern OSes (e.g. CoreOS) seem to follow the patterns. CoreOS also do everything in their power to prevent you from mounting /usr as writeable. Perhaps that doesn't pass your bar for 'real' though since it's not globally implemented ;)