The best way to
understand these concepts is to look at a practical case. Suppose
you have just purchased a brand new hard disk with no partitions on
it. Your Mandrakelinux partition is completely full, and rather
than starting again from scratch, you decide to move a whole section
of the tree structure[20] to
your new hard disk. Because your new disk has a large capacity, you
decide to move your biggest directory to it:
/usr
. But first, a bit of theory.