Disk image

A disk image is a computer file that represents the content of a data storage device. It is most often a file system embedded as a file within another file system. The term has been generalized to cover any such file, whether drawn from an actual physical storage device or not.

Disk images can be either raw or compressed with some kind of compression algorithm like LZW. Images of CD-ROMs most often carry the file name extension .iso, referring to the ISO 9660 file system commonly used on such discs.

A common use of disk images is for remote distribution of software such as Linux distributions: installation floppy disks or CD-ROMs can be recorded as disk image files, transferred over the Internet, and the contents of the original disk(s) duplicated exactly by end users with their own floppy or CD-R drives.

Another common use is to provide virtual disk drive space to be used by emulators and virtual machines.

See also: ISO image, RaWrite, RaWrite2.