The Raspberry Pi comes equipped with a Secure Digital (SD) card port and to begin with we will run the operating system from an SD card. It is possible to use an USB hard drive as we discussed earlier, which are generally faster and in Chapter 7, Going Further we will discuss this in more detail. For the earlier chapters, however, the SD card is convenient as it is easy to quickly clone for multiple devices, takes up no extra desk space, and leaves the USB ports free for connecting a mouse and keyboard for debugging issue, if for example, you cannot login to the device via the network.
There is a range of SD cards available in the market in a variety of sizes. You will need to use an SD card of at least 2 GB.
You can find a guide to supported SD card brands and models at eLinux's Raspberry Pi Wiki:
http://elinux.org/RPi_SD_cards
It is also possible to purchase an SD card with a pre-installed operating system; however we recommend following...