mount a file system linux command code example

Example: mount a filesystem under another filesystem linux

When you mount a filesystem on a directory /mpoint, you can no longer access 
files under /mpoint directly. /mpoint now refers to the root of the newly 
mounted filesystem, and no longer points to the directory that it did earlier.
The contents of that directory are not deleted, they just become invisible. And 
executing ls /mpoint will now show the contents under the new file system.