Mount a directory in another location

_$: mount --bind <olddir> <newdir>
_$: umount <newdir>

Example:

_$: mkdir /home/<user>/tmp
_$: mount --bind /tmp  /home/<user>/tmp
_$: echo "TEST" > /tmp/test
_$: cat /home/<user>/tmp/test
_$: cat /etc/mtab
...
/tmp /home/<user>/tmp none rw,bind 0 0
_$: umount /home/<user>/tmp