Malaysian Open Source Centre

Live CD

A live CD or live DVD is a CD or DVD containing a bootable computer operating system. Live CDs are unique in that they have the ability to run a complete, modern operating system on a computer lacking mutable secondary storage, such as a hard disk drive. Live USB flash drives are similar to live CDs, but often have the added functionality of automatically and transparently writing changes back to their bootable medium.

The term "live" derives from the fact that these CDs each contain a complete, functioning and operational operating system on the distribution medium.

While a live CD typically does not alter the operating system or files already installed on a computer's hard drive, many Live CDs include mechanisms and utilities for altering the host computer's hard drive, including permanent installation. This is important for the system management aspect of live CDs, such as removing viruses, drive imaging, and system recovery.

The default option, however, is to allow the user to return the computer to its previous state when the live CD is ejected and the computer is rebooted. It is able to run without permanent installation by placing the files that typically would be stored on a hard drive into RAM, typically in a RAM disk. However, this does cut down on the RAM available to applications, reducing performance somewhat. As of 2007, certain live CDs run a graphical user interface in as little as 32MB RAM.