Symlink two real directories with files in both

Question

I have two directories, with files in both of them:

./read/pub/
        |- file1

and

./write/pub/
        |- dir1/
        |- file2
        |- file3

I need to create a symlink so that all the content in ./write/pub/ is readable also in ./read/pub/, but I would like some kind of hybrid directory.

Is it possible to symlink directly the real directory ./read/pub/ to ./write/pub/, instead of symlinking all its content? So I could have the possibility to put files in both directory and not have the files in ./read/pub/ present in ./write/pub/, AND the new files in ./write/pub/ will appear automatically in the ./read/pub/ directory, without recreating the symlinks each time.

PS - I don't think it is possible, but would like to know if you have some kind of solution isntead.

Answer 1

What you want can be achieved by a union mount.

The information in the wikipedia article should get you started: https://en.wikipedia.org/wiki/Union_mount