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| '''IMG file format''' may refer to several different and incompatible file formats, which usually just have the use of the ''.img'' ] in common: | '''IMG file format''' may refer to several different and incompatible file formats, which usually just have the use of the ''.img'' ] in common: | ||
| * |
* Binary files used to store raw ] of ]s or ]s. | ||
| * The ] proprietary ] file format, used by ] for ]. | |||
| * ], used by ] GPS devices. | * ], used by ] GPS devices. | ||
| * The GEM Raster file format<ref></ref>, an image file format used to store ] digital images on the ] operating environment. | * The GEM Raster file format<ref></ref>, an image file format used to store ] digital images on the ] operating environment. | ||
| * Other ] file formats used by different graphics software packages. | * Other ] file formats used by different graphics software packages. | ||
| This article will focus on raw disk image |
This article will focus on the first format indicated above, raw disk image files that use the extension ''.img''. | ||
| ==IMG raw disk image format== | ==IMG raw disk image format== | ||
Revision as of 19:40, 18 April 2013
IMG file format may refer to several different and incompatible file formats, which usually just have the use of the .img file extension in common:
- Binary files used to store raw disk images of floppy disks or hard drives.
- The Apple Disk Image proprietary disk image file format, used by Apple Disk Copy for Mac OS.
- Garmin's map file format, used by Garmin GPS devices.
- The GEM Raster file format, an image file format used to store bitmap digital images on the Graphical Environment Manager operating environment.
- Other digital image file formats used by different graphics software packages.
This article will focus on the first format indicated above, raw disk image files that use the extension .img.
IMG raw disk image format
The .img file extension is used by files which contain raw dumps of a disk, commonly called disk images. Since a raw image consists of a sector-by-sector binary copy of the source medium, the actual format of the file contents will depend on the file system from which the raw disk image was created. A similar file extension, .ima, is used to refer to the same type of raw disk image files by some tools.
The .img file extension was originally associated to floppy disk raw disk images only, though it was later used to refer to hard drive disk images as well.
A variant of the format is called IMZ, and consists of a gzipped version of a raw IMG disk image. These files use the .imz file extension, and are commonly found in compressed images of floppy disks.
A typical raw floppy disk image begins with a FAT boot sector, where the first byte is normally hexadecimal EB (code for a 8bit short jump, offset in the 2nd byte) with third byte 90 (code for a NOP), or rarely EA (code for a 16bit jump, offset in 2nd and 3rd byte). The file size will always be a multiple of the sector size — generally 512 bytes, but other sizes such as 128 and 1024 existed. More precisely the file size corresponds to Cylinders×Heads×(Sectors per track), e.g., 1440KB=80×2×18×512 for 80 cylinders (tracks) and 2 heads (sides) with 18 sectors per track.
Raw disk images of optical media (such as CDs and DVDs) are usually referred to as ISO images, and use the .iso file extension. Functionally, however, they are equivalent to IMG files, though their internal format follows the structure of an optical media file system such as ISO 9660.
Tools
The raw IMG file format is used by several tools:
- Tools such as RaWrite and WinImage use the IMG disk image format to read and write floppy disk images.
- Programs such as ImDisk and Virtual Floppy Drive can mount a raw image of a floppy disk to emulate a floppy drive under Windows.
- mtools allows manipulation of MS-DOS floppy disk images in Unix systems.
- Nero Burning ROM supports reading IMG files for creating bootable CDs.
- Qemu uses it as its default format for hard drive disk images.
- Programs such as dsktrans from the LibDsk suite of command-line tools will convert between raw disk image formats, for Linux, MS-DOS, and Microsoft Windows.
- dd can be used in Linux to create raw disk image files of disks.
References
| Disk image file formats | |
|---|---|
| Comparison of disc image software | |
| Optical discs | |
| Hard disks | |
| Floppy disks | |
| CDDA | Disc Description Protocol |
| Convention: Any item in this table that has the form of "A+B" or "A+B+C" indicates a disk format that spans multiple files, where A contains the bulk of the data, and B and C are sidecar files. | |