The Raspberry Pi runs from an operating system stored on a Secure Digital (SD) card and many different operating systems may be employed. Storage is relatively inexpensive, can be created (flashed), recreated, written to and overwritten with ease.
On the one hand, this is an advantage of the Pi. On the other, the experimental nature of the Pi means more time flashing SD cards. This tutorial shows you how to use a Mac to clone any Raspberry Pi SD card which is particularly useful when you have your OS set up just as you want it.