Live CD

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Image:Gnoppix-0.8.1beta5.png A live CD (or liveCD) is an operating system (usually containing other software as well) stored on a bootable CD or DVD that can be run directly from the CD or DVD drive, without installing into permanent memory, such as a hard drive. (A live CD does not alter the current operating system or files without a user's doing.) The system returns to its previous OS state when the live CD is ejected and the computer is rebooted. It does this by placing the files which 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. This however does cut down on the RAM available to applications, reducing performance somewhat. 256 MB - 512 MB of RAM is recommended. Some live CDs do fine with less.

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Common traits

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

Most live CDs contain a system based on the GNU system and the Linux kernel, but there are also live CDs based on other operating systems, such as Mac OS, Mac OS X, BeOS, FreeBSD, Minix, NetBSD, Plan 9 from Bell Labs, MSDOS or Microsoft Windows, though the legal status of live CDs based on Windows code is dubious. The first OS to support live CD 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 live CDs 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 live CDs use a compressed filesystem image, often with the cloop compressed loopback driver, 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.

Live CDs 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.

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Mini live CDs

A mini live CD, also known as a bootable business card, is a live CD small enough to fit on a CD-ROM that is the size and shape of a business card. Mini live CDs are able to hold about 50 MB, or 100 MB under compression. Damn Small Linux (DSL) is an example of a rich mini live CD operating system that fits onto a 50 MB CD, and includes scripts to optionally install it to a bootable USB key (flash distro) or hard disk. Puppy Linux makes live CDs in the size range of 39 MB to 90 MB.

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Emulation

There are number of emulators on the market that can be used to try a live CD without the need to 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 commercial emulator is VirtualPC.

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List of live CDs

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Apple Macintosh OS-based

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BSD-based

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Linux-based

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Microsoft Windows-based

Microsoft representatives have described third-party efforts at producing Live CDs as being "improperly licensed" uses of Windows. The Microsoft sanctioned MS WinPE product is linked above.

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OpenSolaris-based

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Others

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Rescue and Repair Live CDs

  • SystemRescueCd is a Linux- based CD with tools for Windows and Linux repairs. Based on the 2.6 kernel.
  • 911 Rescue CD Based on DOS with tools for Windows repairs (not technically a live cd)
  • UBCD Free boot cd - ultimate boot cd
  • treehel's FreeSTAR Free UBCD based bootcd with a huge collection of free and open software for windows on it for addition and russian and english windows-interface...
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See also

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External links

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