Optical disc image: Difference between revisions

ISO 9660 image
Filename extensions	.iso, .udf
Internet media type	application/vnd.efi.iso
Uniform Type Identifier (UTI)	public.iso-image
Magic number	Volume descriptor: CD001 at 32769. NSR0 at 38913 or 32769 for UDF.
Type of format	Disk image
Standard	ISO 9660, UDF

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An optical disc image (or ISO image, from the ISO 9660 file system used with CD-ROM media) is a disk image that contains everything that would be written to an optical disc, disk sector by disc sector, including the optical disc file system.^[3] ISO images contain the binary image of an optical media file system (usually ISO 9660 and its extensions or UDF), including the data in its files in binary format, copied exactly as they were stored on the disc. The data inside the ISO image will be structured according to the file system that was used on the optical disc from which it was created.

ISO images can be created from optical discs by disk imaging software, or from a collection of files by optical disc authoring software, or from a different disk image file by means of conversion. Software distributed on bootable discs is often available for download in ISO image format. And like any other ISO image, it may be written to an optical disc such as CD, DVD and Blu-Ray.

Description

Optical-disc images are uncompressed and do not use a particular container format; they are a sector-by-sector copy of the data on an optical disc, stored inside a binary file. Other than ISO 9660 media, an ISO image might also contain a UDF (ISO/IEC 13346) file system (commonly used by DVDs and Blu-ray Discs), including the data in its files in binary format, copied exactly as they were stored on the disc. The data inside the ISO image will be structured according to the file system that was used on the optical disc from which it was created.

The .iso file extension is the one most commonly used for this type of disc images. The .img extension can also be found on some ISO image files, such as in some images from Microsoft DreamSpark; however, IMG files, which also use the .img extension, tend to have slightly different contents. The .udf file extension is sometimes used to indicate that the file system inside the ISO image is actually UDF and not ISO 9660.

ISO files store only the user data from each sector on an optical disc, ignoring the control headers and error correction data, and are therefore slightly smaller than a raw disc image of optical media. Since the size of the user-data portion of a sector (logical sector) in data optical discs is 2,048 bytes, the size of an ISO image will be a multiple of 2,048.

Any single-track CD-ROM, DVD or Blu-ray disc can be archived in ISO format as a true digital copy of the original. Unlike a physical optical disc, an image can be transferred over any data link or removable storage medium. An ISO image can be opened with almost every multi-format file archiver. Native support for handling ISO images varies from operating system to operating system.

With a suitable driver software, an ISO can be "mounted" – allowing the operating system to interface with it, just as if the ISO were a physical optical disc. Most Unix-based operating systems, including Linux and macOS, have this built-in capability to mount an ISO. Versions of Windows, beginning with Windows 8, also have such a capability.^[4] For other operating systems, separately available software drivers can be installed to achieve the same objective.

Multiple-track images

A CD can have multiple tracks, which can contain computer data, audio, or video. File systems such as ISO 9660 are stored inside one of these tracks. Since ISO images are expected to contain a binary copy of the file system and its contents, there is no concept of a "track" inside an ISO image, since a track is a container for the contents of an ISO image. This means that CDs with multiple tracks can not be stored inside a single ISO image; at most, an ISO image will contain the data inside one of those multiple tracks, and only if it is stored inside a standard file system.

This also means that audio CDs, which are usually composed of multiple tracks, can not be stored inside an ISO image. Furthermore, not even a single track of an audio CD can be stored as an ISO image, since audio tracks do not contain a file system inside them, but only a continuous stream of encoded audio data. This audio is stored on sectors of 2352 bytes different from those that store a file system and it is not stored inside files; it is addressed with track numbers, index points and a CD time code that are encoded into the lead-in of each session of the CD-Audio disc.

Video CDs and Super Video CDs require at least two tracks on a CD, so it is also not possible to store an image of one of these discs inside an ISO image file, however an .IMG file can achieve this.

Formats such as CUE/BIN, CCD/IMG and MDS/MDF formats can be used to store multi-track disc images, including audio CDs. These formats store a raw disc image of the complete disc, including information from all tracks, along with a companion file describing the multiple tracks and the characteristics of each of those tracks. This would allow an optical media burning tool to have all the information required to correctly burn the image on a new disc. For audio CDs, one can also transfer the audio data into uncompressed audio files like WAV or AIFF, optionally reserving the metadata (see CD ripping).

Most software that is capable of writing from ISO images to hard disks or recordable media (CD / DVD / BD) is generally not able to write from ISO disk images to flash drives. This limitation is more related to the availability of software tools able to perform this task, than to problems in the format itself. However, since 2011, various software has existed to write raw image files to USB flash drives.^[5]^[6]

Uses

.ISO files are commonly used in emulators to replicate a CD image. Emulators such as Dolphin and PCSX2 use .iso files to emulate Wii and GameCube games, and PlayStation 2 games, respectively.^[7]^[8] They can also be used as virtual CD-ROMs for hypervisors such as VMware Workstation or VirtualBox. Other uses are burning disk images of operating systems to physical install media.

References

^ Siyuan, Fu (24 January 2017). "application/vnd.efi.iso". IANA. Retrieved 18 July 2023.
^ "File Signatures". www.garykessler.net. Archived from the original on 2020-07-03. Retrieved 2020-07-01.
^ Fisher, Tim (24 April 2018). "What Is an ISO File?". Lifewire. Archived from the original on 23 June 2018. Retrieved 23 June 2018.
^ "Windows 8 Explorer will support native mounting of ISO and VHD". ExtremeTech. Archived from the original on 2012-05-31. Retrieved 2012-05-21.
^ "ISO image to USB conversion". ISO to USB burning tool. Archived from the original on 15 February 2015. Retrieved 15 February 2015.
^ "How to Setup Windows 7 or Windows 8 from USB drive?". PowerISO. Archived from the original on 20 June 2016. Retrieved 15 February 2015.
^ "What dump formats are supported by Dolphin?". Dolphin Emulator Project. Archived from the original on 4 March 2017. Retrieved 11 March 2021.
^ "So how do I use it? - PCSX2". PCSX2 Team. Archived from the original on 9 March 2021. Retrieved 11 March 2021.

External links

How to write ISO files to CD, DVD, and BD with Linux using genisoimage, wodim, growisofs, etc.

[1] Siyuan, Fu (24 January 2017). "application/vnd.efi.iso". IANA. Retrieved 18 July 2023.

[2] "File Signatures". www.garykessler.net. Archived from the original on 2020-07-03. Retrieved 2020-07-01.

[3] Fisher, Tim (24 April 2018). "What Is an ISO File?". Lifewire. Archived from the original on 23 June 2018. Retrieved 23 June 2018.

[4] "Windows 8 Explorer will support native mounting of ISO and VHD". ExtremeTech. Archived from the original on 2012-05-31. Retrieved 2012-05-21.

[5] "ISO image to USB conversion". ISO to USB burning tool. Archived from the original on 15 February 2015. Retrieved 15 February 2015.

[6] "How to Setup Windows 7 or Windows 8 from USB drive?". PowerISO. Archived from the original on 20 June 2016. Retrieved 15 February 2015.

[7] "What dump formats are supported by Dolphin?". Dolphin Emulator Project. Archived from the original on 4 March 2017. Retrieved 11 March 2021.

[8] "So how do I use it? - PCSX2". PCSX2 Team. Archived from the original on 9 March 2021. Retrieved 11 March 2021.

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@@ Line 1: / Line 1: @@
+{{short description|Archive file of an optical disc}}
-[[Category:Archive formats]]
+{{Multiple issues|
-[[Category:Disk images]]
+{{More citations needed|date=August 2011}}
+{{Original research|date=November 2020}}
+{{Essay-like|date=November 2020}}
+}}
+{{ infobox file format
+| name          = ISO 9660 image
+| mime          = application/vnd.efi.iso<ref>{{cite web |last1=Siyuan |first1=Fu |title=application/vnd.efi.iso |url=https://www.iana.org/assignments/media-types/application/vnd.efi.iso |publisher=[[IANA]] |access-date=18 July 2023 |date=24 January 2017}}</ref>
+| magic         = [[ISO 9660#Volume descriptor|Volume descriptor]]: {{code|CD001}} at 32769. {{code|NSR0}} at 38913 or 32769 for UDF.<ref>{{cite web |title=File Signatures |url=https://www.garykessler.net/library/file_sigs.html |website=www.garykessler.net |access-date=2020-07-01 |archive-date=2020-07-03 |archive-url=https://web.archive.org/web/20200703084445/https://www.garykessler.net/library/file_sigs.html |url-status=live }}</ref>
+| standard      = [[ISO 9660]], [[Universal Disk Format|UDF]]
+| extensions    = .iso, .udf
+| url           =
+| type code     =
+| uniform type  = public.iso-image
+| owner         =
+| genre         = [[Disk image]]
+| container for =
+| contained by  =
+| extended from =
+| extended to   =
+}}
+An '''optical disc image''' (or '''ISO image''', from the [[ISO 9660]] file system used with [[CD-ROM]] media) is a [[disk image]] that contains everything that would be written to an [[optical disc]], [[disk sector]] by disc sector, including the optical disc [[file system]].<ref>{{cite web | url=https://www.lifewire.com/iso-file-2625923 | title=What Is an ISO File? | website=Lifewire | date=24 April 2018 | last=Fisher | first=Tim | access-date=23 June 2018 | archive-date=23 June 2018 | archive-url=https://web.archive.org/web/20180623113439/https://www.lifewire.com/iso-file-2625923 | url-status=live }}</ref> ISO images contain the binary image of an optical media [[file system]] (usually [[ISO 9660]] and its extensions or [[Universal Disk Format|UDF]]), including the data in its files in binary format, copied exactly as they were stored on the disc. The data inside the ISO image will be structured according to the file system that was used on the optical disc from which it was created.
+ISO images can be created from optical discs by [[Comparison of disc image software|disk imaging software]], or from a collection of [[computer file|files]] by [[optical disc authoring software]], or from a different [[disk image#File formats|disk image file]] by means of [[data conversion|conversion]]. Software distributed on bootable discs is often available for download in ISO image format. And like any other ISO image, it may be written to an optical disc such as CD, DVD and Blu-Ray.
-An optical disc image refers to a digital representation of the content stored on an optical disc, such as a CD, DVD, or Blu-ray disc. It is commonly known as an ISO image, derived from the file extension ".iso" used to identify these files. ISO images allow for the preservation, distribution, and reproduction of the original disc's contents in a single, easy-to-manage file. This article provides an overview of optical disc images, their creation, uses, and their significance in the digital world.
-== Overview ==
+== Description ==
-Optical discs have long been a popular medium for storing and distributing software, games, movies, and other forms of multimedia. However, physical discs can be susceptible to damage, loss, or obsolescence over time. To overcome these limitations, optical disc images were introduced as a means to replicate and store the contents of a disc in a digital format.
+Optical-disc images are uncompressed and do not use a particular container format; they are a [[disk sector|sector]]-by-sector copy of the data on an optical disc, stored inside a binary file. Other than ISO 9660 media, an ISO image might also contain a [[Universal Disk Format|UDF]] (ISO/IEC 13346) file system (commonly used by [[DVD]]s and [[Blu-ray Disc]]s), including the data in its files in binary format, copied exactly as they were stored on the disc. The data inside the ISO image will be structured according to the [[file system]] that was used on the optical disc from which it was created.
-An optical disc image is essentially a sector-by-sector copy of the entire disc's contents, including its file system, metadata, and data tracks. It is stored as a single file, typically with the .iso extension, which contains a byte-for-byte representation of the original disc. This file can then be used to create an identical copy of the original disc or be mounted virtually as a virtual disc drive on a computer.
+The ''.iso'' [[file extension]] is the one most commonly used for this type of disc images. The ''.img'' extension can also be found on some ISO image files, such as in some images from Microsoft [[DreamSpark]]; however, [[IMG (file format)|IMG files]], which also use the ''.img'' extension, tend to have slightly different contents. The ''.udf'' file extension is sometimes used to indicate that the file system inside the ISO image is actually UDF and not ISO 9660.
-== Creation of Optical Disc Images ==
-Creating an optical disc image involves using specialized software that can read the disc's contents and create a digital copy. There are various software tools available for this purpose, both commercial and open-source. Popular examples include Nero Burning ROM, ImgBurn, and Daemon Tools.
+ISO files store only the user data from each sector on an optical disc, ignoring the [[CD-ROM#CD-ROM format|control headers]] and error correction data, and are therefore slightly smaller than a raw disc image of optical media. Since the size of the user-data portion of a sector (logical sector) in data optical discs is 2,048 bytes, the size of an ISO image will be a multiple of 2,048.
-The process of creating an optical disc image typically involves the following steps:
+Any single-[[Track (CD)|track]] [[CD-ROM]], [[DVD]] or [[Blu-ray]] disc can be archived in ISO format as a true digital copy of the original. Unlike a physical optical disc, an image can be transferred over any data link or removable storage medium. An ISO image can be opened with almost every multi-format [[file archiver]]. Native support for handling ISO images varies from operating system to operating system.
-# Launch the disc imaging software and select the option to create an image or copy a disc.
-# Choose the source optical disc from which the image will be created.
-# Specify the destination folder and filename for the resulting ISO image.
-# Configure any additional settings, such as compression level or image format, if applicable.
-# Start the imaging process and wait for it to complete.
+With a suitable [[Device driver|driver]] software, an ISO can be "[[Mount (computing)|mounted]]" – allowing the operating system to interface with it, just as if the ISO were a physical optical disc. Most [[Unix]]-based operating systems, including [[Linux]] and [[macOS]], have this built-in capability to mount an ISO. Versions of Windows, beginning with [[Windows 8]], also have such a capability.<ref>{{Cite web |url=http://www.extremetech.com/computing/94370-windows-8-explorer-will-support-native-mounting-of-iso-and-vhd |title=Windows 8 Explorer will support native mounting of ISO and VHD |publisher=[[ExtremeTech]] |access-date=2012-05-21 |archive-date=2012-05-31 |archive-url=https://web.archive.org/web/20120531075941/http://www.extremetech.com/computing/94370-windows-8-explorer-will-support-native-mounting-of-iso-and-vhd |url-status=live }}</ref> For other operating systems, separately available software drivers can be installed to achieve the same objective.
-Once the imaging process is finished, a complete replica of the original disc is stored as an ISO image file on the computer's storage medium.
+== Multiple-track images ==
-== Uses and Significance ==
-Optical disc images have become widely adopted due to their convenience, portability, and versatility. They offer several benefits and are commonly used for various purposes:
+A CD can have multiple [[track (CD)|tracks]], which can contain computer data, audio, or video. [[File system]]s such as [[ISO 9660]] are stored inside one of these tracks. Since ISO images are expected to contain a binary copy of the file system and its contents, there is no concept of a "track" inside an ISO image, since a track is a container for the contents of an ISO image. This means that CDs with multiple tracks can not be stored inside a single ISO image; at most, an ISO image will contain the data inside one of those multiple tracks, and only if it is stored inside a standard file system.
-# Preservation and Backup: ISO images allow for the preservation and backup of valuable or rare discs. By creating a digital copy, users can safeguard the content against physical damage, loss, or degradation of the original disc.
-# Distribution: ISO images are extensively used for distributing software, games, and other multimedia content. Instead of shipping physical discs, developers and publishers can provide a downloadable ISO image, enabling users to create their own copies.
-# Virtualization and Emulation: ISO images can be mounted virtually, creating a virtual disc drive on a computer. This feature allows users to access the contents of the disc without the need for physical media. Virtualization software, such as VirtualBox or VMware, can utilize ISO images to run operating systems or software installations in a virtual environment.
-# Gaming: ISO images are commonly used in the gaming community for running games without the need for the original physical disc. This practice, often referred to as "game emulation," enables users to play retro or out-of-print games on modern hardware.
-# Media Playback: Media players, such as VLC or Kodi, can open ISO images directly and play the contents as if they were reading from a physical disc. This feature is useful for watching movies, listening to music, or viewing other multimedia content stored in ISO format.
+This also means that [[Compact Disc Digital Audio|audio CD]]s, which are usually composed of multiple tracks, can not be stored inside an ISO image. Furthermore, not even a single track of an audio CD can be stored as an ISO image, since audio tracks do not contain a file system inside them, but only a continuous stream of encoded audio data. This audio is stored on [[Track (CD)#Subchannels|sectors of 2352 bytes]] different from those that store a file system and it is not stored inside files; it is addressed with ''track numbers'', ''index points'' and a ''CD time code'' that are encoded into the [[Lead-in (CD)|lead-in]] of each session of the CD-Audio disc.
-== Legal Considerations ==
-While optical disc images offer various legitimate uses, it is important to note that the creation, distribution, and use of ISO images can raise legal considerations. Unauthorized duplication or distribution of copyrighted material, including software or movies, is illegal in many jurisdictions. Users should ensure they have the necessary rights or permissions to create or use ISO images of copyrighted content.
+[[Video CD]]s and [[Super Video CD]]s require at least two tracks on a CD, so it is also not possible to store an image of one of these discs inside an ISO image file, however an .IMG file can achieve this.
+Formats such as [[Cue sheet (computing)|CUE/BIN]], [[CloneCD Control File|CCD/IMG]] and [[MDF and MDS file pair|MDS/MDF]] formats can be used to store multi-track disc images, including audio CDs. These formats store a raw disc image of the complete disc, including information from all tracks, along with a companion file describing the multiple tracks and the characteristics of each of those tracks. This would allow an optical media burning tool to have all the information required to correctly burn the image on a new disc. For audio CDs, one can also transfer the audio data into uncompressed audio files like [[WAV]] or [[Audio Interchange File Format|AIFF]], optionally reserving the metadata (see [[Ripping|CD ripping]]).
+Most software that is capable of writing from ISO images to hard disks or recordable media (CD / DVD / BD) is generally not able to write from ISO disk images to [[USB flash drive|flash drive]]s. This limitation is more related to the availability of software tools able to perform this task, than to problems in the format itself. However, since 2011, various software has existed to write raw image files to USB flash drives.<ref>{{cite web | url=http://imagetousb.com/iso-image-to-usb-conversion/ | title=ISO image to USB conversion | publisher=ISO to USB burning tool | access-date=15 February 2015 | url-status=dead | archive-url=https://web.archive.org/web/20150215102916/http://imagetousb.com/iso-image-to-usb-conversion/ | archive-date=15 February 2015 }}</ref><ref>{{cite web | url=http://www.poweriso.com/tutorials/how-to-make-win7-bootable-usb-drive.htm | title=How to Setup Windows 7 or Windows 8 from USB drive? | publisher=PowerISO | access-date=15 February 2015 | archive-date=20 June 2016 | archive-url=https://web.archive.org/web/20160620222349/http://www.poweriso.com/tutorials/how-to-make-win7-bootable-usb-drive.htm | url-status=live }}</ref>
+== Uses ==
+.ISO files are commonly used in [[emulators]] to replicate a [[CD]] image. Emulators such as [[Dolphin (emulator)|Dolphin]] and [[PCSX2]] use .iso files to emulate [[Wii]] and [[GameCube]] games, and [[PlayStation 2]] games, respectively.<ref>{{cite web | url=https://dolphin-emu.org/docs/faq/#what-dump-formats-are-supported-dolphin | title=What dump formats are supported by Dolphin? | publisher=Dolphin Emulator Project | access-date=11 March 2021 | archive-date=4 March 2017 | archive-url=https://web.archive.org/web/20170304193029/https://dolphin-emu.org/docs/faq/#what-dump-formats-are-supported-dolphin | url-status=live }}</ref><ref>{{cite web | url=https://pcsx2.net/getting-started.html | title=So how do I use it? - PCSX2 | publisher=PCSX2 Team | access-date=11 March 2021 | archive-date=9 March 2021 | archive-url=https://web.archive.org/web/20210309011752/https://pcsx2.net/getting-started.html | url-status=live }}</ref> They can also be used as virtual CD-ROMs for hypervisors such as [[VMware Workstation]] or [[VirtualBox]]. Other uses are burning disk images of operating systems to physical install media.
+== See also ==
+* [[Comparison of disc image software]]
+* [[Live USB]]
+* [[No-disc crack]]
 == References ==
+{{refs}}
-# Smith, John. "The Evolution of Optical Discs." Journal of Digital Preservation, vol. 25, no. 2, 2020, pp. 45-62.
-# Johnson, Mary. "Understanding Optical Disc Imaging and its Applications." International Conference on Digital Preservation Proceedings, 2018, pp. 123-137.
+== External links ==
-# Brown, David. "The Legality of ISO Image Usage." Journal of Copyright Law, vol. 30, no. 3, 2019, pp. 78-95.
+* [http://wiki.archlinux.org/index.php/Optical_disc_drive How to write ISO files to CD, DVD, and BD with Linux using genisoimage, wodim, growisofs, etc.]
+{{Disk images}}
+[[Category:Archive formats]]
+[[Category:Disk images]]

v t e Disk image file formats
Comparison of disc image software
Optical discs	BIN+CUE DAA IMG+CCD+SUB ISO ISZ MDF+MDS MDX NRG UIF
Hard disks	DMG FVD IMG ISO NDIF QCOW UDIF VDI VHD VMDK WIM
Floppy disks	ADF, ADZ DC42, DART DMS IMG, IMA, IMZ VFD
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.