debgat:~/test# mkdir dir1 
debgat:~/test# mkdir dir2
debgat:~/test# ll -i
total 8
33763 drwxr-xr-x  2 root root 4096 Dec 19 18:12 dir1
33764 drwxr-xr-x  2 root root 4096 Dec 19 18:12 dir2
debgat:~/test# mount --bind dir1/ dir2/
debgat:~/test# ll -i
total 8
33763 drwxr-xr-x  2 root root 4096 Dec 19 18:12 dir1
33763 drwxr-xr-x  2 root root 4096 Dec 19 18:12 dir2