All computers except the earliest digital computers are built with some form of minimal built-in loader, which loads a program or succession of programs from a storage medium, which then operate the computer. Initially a read-only medium such as punched tape or punched cards was used for initial program load. With the introduction of inexpensive read-write storage, read-write
floppy disks and hard disks were used as
boot media. After the introduction of the
audio compact disc, it was adapted for use as a medium for storing and distributing large amounts of computer data. This data may also include application and operating-system software, sometimes packaged and archived in compressed formats. Later, it was seen to be convenient and useful to boot the computer directly from compact disc, often with a minimal working system to install a full system onto a hard drive. While there are read-write optical discs, either mass-produced read-only discs or write-once discs were used for this purpose. The first Compact Disc drives on personal computers were generally much too slow to run complex operating systems; computers were not designed to boot from an
optical disc. When operating systems came to be distributed on compact discs, either a
boot floppy or the CD itself would boot specifically, and only, to install onto a hard drive. Early examples of operating systems which could be booted directly from CD-ROM are the
FM Towns OS, and the Desktop-VMS distribution of
VMS, both of which were first released in 1989.
Linux Although early developers and users of distributions built on top of the
Linux kernel could take advantage of cheap optical disks and rapidly declining prices of CD drives for personal computers, the
Linux distribution CDs or "distros" were generally treated as a collection of installation packages that would first need to be permanently installed to hard disks on the target machine. However, in the case of these distributions built on top of the Linux kernel, the
free operating system was meeting resistance in the consumer market because of the perceived difficulty, effort, and risk involved in installing an additional partition on the hard disk, in parallel with an existing operating system installation. The term "live CD" was coined because, after typical PC RAM was large enough and 52x speed CD drives and CD burners were widespread among PC owners, it finally became convenient and practical to boot the kernel and run
X11, a window manager and GUI applications directly from a CD without disturbing the OS on the hard disk. This was a new and different situation for Linux than other operating systems, because the updates/upgrades were being released so quickly, different distributions and versions were being offered online, and especially because users were burning their own CDs. The first
Linux-based 'Live CD' was
Yggdrasil Linux first released in beta form 1992~1993 (ceased production in 1995), though in practice its functionality was hampered due to the low throughput of contemporary CD-ROM drives.
DemoLinux, released in 1998, was the first Linux distribution specially designed as a live CD. The
Linuxcare bootable business card, first released in 1999, was the first Live CD to focus on system administration, and the first to be distributed in the bootable business card form factor. ,
Finnix (first released in spring 2000) is the oldest Live CD still in production. Shortly followed by
Knoppix, a
Debian-derived Linux distribution, also still produced, it first released in fall 2000 and found popularity as both a
rescue disk system and as a primary distribution in its own right. Since 2003, the popularity of live CDs has increased substantially, partly due to Linux Live scripts and
remastersys, which made it very easy to build customized live systems. Most of the popular
Linux distributions now include a live CD variant, which in some cases is also the preferred installation medium. == Uses ==