LiveDistro

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(Redirected from LiveCD)

"Live CD" redirects here. For musical recordings, see Live album.

Gnoppix 0.8.1-beta5 running Epiphany 1.4.0 under GNOME, with Gaim connected to the freenode IRC Network

LiveDistro 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 bootable media such as a CD-ROM (Live CD), DVD (Live DVD), USB flash drive (Live USB), among others.

The term "live" derives from the fact that it does not reside on a hard drive. Rather, it is "brought to life" upon boot without having to be physically installed onto a hard drive.

A LiveDistro does not alter the current operating system or files unless the user specifically requests it. The system returns to its previous state when the LiveDistro 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. At least 256 MB of RAM is recommended, but some LiveDistros do fine with less.

It is often said LiveDistros are a good way to demo or preview an operating system without having to install it to a hard drive.

1 Common traits
2 History
3 Emulation
4 See also
5 External links

[edit] Common traits

Some LiveDistros come with an installation utility launchable from a desktop icon that can optionally install the system on a hard drive or USB keydrive. Most LiveDistros can access the information on internal and/or external hard drives, diskettes and USB Flash drives.

Most LiveDistros are based on Linux, but there are also LiveDistros based on other operating systems, such as Mac OS, Mac OS X, Solaris, BeOS, ReactOS, FreeBSD, Minix, NetBSD, Plan 9 from Bell Labs, MSDOS or Microsoft Windows. The legal status of LiveDistros based on Windows code is dubious^{[citation needed]}. The first OS to support LiveDistro operations appears to have been Mac OS 7 on a CD and any other user-created Macintosh CD with a System Folder, which could be brought to a full desktop from a CD-ROM, in 1991.

The syslinux utility is used to boot Linux based LiveDistros as well as Linux floppies. On a PC, a bootable CD generally conforms to the El Torito specification which treats a special file on the disc (possibly hidden) as a floppy diskette image. Many Linux based LiveDistros use a compressed filesystem image, often with the cloop compressed loopback driver, or squashfs compressed filesystem, generally doubling effective storage capacity, although slowing application start up. The resulting environment can be quite rich: typical Knoppix systems include around 1,200 separate software packages.

LiveDistros have a reputation for supporting advanced auto-configuration and plug-and-play functionality. This is necessary so as to avoid requiring the user to configure the system each time it boots, and to make them easily usable by those who are new to the operating system.

[edit] History

The first GNU/Linux-based LiveCD was French DemoLinux (released in 1998). The first well-known LiveCD was Knoppix (released in 2003). Since 2003, the popularity of LiveCDs has increased substantially.

[edit] Emulation

There are number of emulators (the article virtual machine also contains a list of them) on the market that can be used to try a LiveDistro 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 i386 emulator is VMware. Others include QEMU, PearPC and Bochs which can all also emulate the x86 and/or PowerPC platforms, although due to their software emulation methods, they are slower than the hardware alternatives. Another emulator that has turned from commercial to freeware is Microsoft Virtual PC.