It is not allowed to create a hard link for a dir.
But the soft like will not work, if I later change the name of the dir. How would you solve the dilemma?
Are there applications which can
make soft links work after changing the dir's name? Or
make hard links work for dirs?
mount --bind
does the thing you want. There are also slave, shared, and unbindable mount types. You can move mounts. You can do these things recursively as well - as in, you can mount a tree and all of its submounts elsewhere as simply asmount --rbind