You could achieve the same thing with sym links, which is basically what Apple does with newer versions of macOS. The main OS partition (/) is read only, essent

You could achieve the same thing with sym links, which is basically what Apple does with newer versions of macOS. The main OS partition (/) is read only, essentially immutable (unless you disable SIP.) There is a writeable volume mounted on /private (in a funky way, using "firm links".) /etc, /var, /home, and a couple others are symlinks to /private/etc, /private/var, /private/home ... They do some funky stuff with /usr/local and a few other directories, too. This person seems to explain it: http://www.swiftforensics.com/2019/10/macos-1015-volumes-firmlink-magic.html http://www.swiftforensics.com/2019/10/macos-1015-volumes-fir...