Guide to Live CD

Live CD is a generic term for an operating system distribution that is executed upon boot, without installation on a hard drive. Typically, it is stored on a bootable medium, such as a CD-ROM (Live CD), DVD (Live DVD), Floppy (Live floppy), USB flash drive (Live USB), among others

A LiveCD does not alter the current operating system or files unless the user specifically requests it. The system returns to its previous state when the LiveCD is ejected and the computer is rebooted. It does this by placing the files that typically would be stored on a hard drive into temporary memory, such as a ram disk. In fact, a hard drive is not needed at all. However, this does cut down on the RAM available to applications, reducing performance somewhat. Certain LiveCDs run a GUI in as little as 32Mb RAM.

A LiveCD may be used to "demo" or "test drive" a particular operating system for those users who are unfamiliar with it. Experienced users of the operating system may also use a LiveCD to determine whether and to what extent a particular operating system version is compatible with their current hardware configuration and peripherals.

File system

A Read-only file system, such as on a CD-ROM has the drawback of being unable to save any current working data. For this reason, a read-only file system is often merged with a temporary writable file system in the form of a ramdisk. Often the default Linux directories "/home" (containing users' personal files and configuration files) and "/var" (containing variable data) are kept in ramdisk, because the system updates them frequently.

Hardware detection

LiveDistros have to be able to detect a wide variety of hardware (including network cards, graphic cards etc.). This is easily achieved nowadays by udev or hotplug, which is a common part of all distributions

Emulation

There are number of emulators on the market that can be used to try a LiveCD without the need to install it on a medium or burn it to a CD or boot it on the computer. The most widely supported emulator is VMware. (Click here for more info)
VirtualBox is only a virtualization box, not an emulator which is far speedier than emulation and a good alternative. Some emulators are distributed as free software under the GPL license. Others, such as VMware, are distributed under for-fee proprietary licenses. An emulator that has turned from commercial to freeware is Microsoft Virtual PC.

Learn how to create a Linux Live CD