root@phschafft-x2:/tmp/mount-tests# ls -laFhi total 20K 3940458 drwxr-xr-x 3 root root 4.0K Oct 16 15:39 ./ 3932161 drwxrwxrwt 63 root root 12K Oct 16 15:39 ../ 3932567 -rw-r--r-- 1 root root 0 Oct 16 15:38 a 3932653 -rw-r--r-- 1 root root 0 Oct 16 15:38 b 3940459 drwxr-xr-x 2 root root 4.0K Oct 16 15:39 c/ root@phschafft-x2:/tmp/mount-tests# mount --bind a b root@phschafft-x2:/tmp/mount-tests# ls -laFhi total 16K 3940458 drwxr-xr-x 2 root root 4.0K Oct 16 15:38 ./ 3932161 drwxrwxrwt 63 root root 12K Oct 16 15:38 ../ 3932567 -rw-r--r-- 1 root root 0 Oct 16 15:38 a 3932567 -rw-r--r-- 1 root root 0 Oct 16 15:38 b 3940459 drwxr-xr-x 2 root root 4.0K Oct 16 15:39 c/ root@phschafft-x2:/tmp/mount-tests# umount b root@phschafft-x2:/tmp/mount-tests# mount --bind c b mount: /tmp/mount-tests/b: mount point is not a directory. dmesg(1) may have more information after failed mount system call.