A file with the extension .dmg (an abbreviation for disk image) uses a disk image format commonly found on Mac OS X. The format allows secure password protection as well as file compression and hence serves both security and file distribution functions. Its most common function is the distribution of software over the Internet. When opened, DMG files are "mounted" as a drive within the Finder. Image File history File links Apple_Disk_Image. ... A filename extension is a suffix to the name of a computer file applied to show its format. ... Multipurpose Internet Mail Extensions (MIME) is an Internet Standard that extends the format of e-mail to support: text in character sets other than US-ASCII; non-text attachments; multi-part message bodies; and header information in non-ASCII character sets. ... A Uniform Type Identifier (UTI) is a string that uniquely identifies the type of a class of items. ... Apple Inc. ... A disk image is a computer file containing the complete contents and structure of a data storage medium or device, such as a Hard drive, CD or DVD. The term has been generalized to cover any such file, whether originated from an actual physical storage device or not. ... Mac OS X (official IPA pronunciation: ) is a line of proprietary, graphical operating systems developed, marketed, and sold by Apple Inc. ... In computer science, data compression or source coding is the process of encoding information using fewer bits (or other information-bearing units) than a more obvious representation would use, thanks to specific encoding schemes. ... Computer software (or simply software) refers to one or more computer programs and data held in the storage of a computer for some purpose. ... Mounting, in computer science, is the process of making a file system ready for use by the operating system, typically by reading certain index data structures from storage into memory ahead of time. ... The Finder is the default application program used on the Mac OS and Mac OS X operating systems that is responsible for the overall user-management of files, disks, network volumes and the launching of other applications. ...

DMG files can be easily created (with or without encryption) using utilities that are included in OS X: Disk Utility in Mac OS X v10.4 and 10.3 or Disk Copy in earlier versions. These utilities also use DMG files as images for burning CDs and DVDs. DMG files may also be managed via the command line using the hdiutil utility. “Cipher” redirects here. ... Disk Utility is the name of a utility created by Apple for performing disk-related tasks in Mac OS X. These tasks include: the creation of disk images; mounting, unmounting, and ejecting disks (including both hard disks, removable media and disk images); enabling or disabling journaling; verifying a disks... Mac OS X version 10. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Disk Utility application icon Disk Utility is the name of a utility for performing disk-related tasks in Mac OS X. These tasks include: the creation of disk images; mounting, unmounting, and ejecting disks (including both hard disks, removable media and disk images); enabling or disabling journaling; verifying a disk... This article or section does not adequately cite its references or sources. ...

DMG files are published with a MIME type of application/x-apple-diskimage. As many web server administrators tend to be less knowledgeable about Apple-specific file types, this MIME type is not set, often resulting in the user experience of attempting to download DMG files as text directly to the browser window, forcing the use of an option-click or a similar workaround to download the file. For this reason, DMG files may be distributed as bzip2 (.dmg.bz2) or ZIP (.dmg.zip) files. These wrappers typically don't compress the file further, but rather help ensure that the files are handled correctly by the server and browser software. Multipurpose Internet Mail Extensions (MIME) is an Internet Standard for the format of e-mail. ... The correct title of this article is . ... The ZIP file format is a popular data compression and archival format. ...

Utilities exist to convert DMG files into ISO images, however, DMG files do often contain other types of disk images such as HFS+ volumes. This article does not cite any references or sources. ... HFS Plus or HFS+ is a file system developed by Apple Computer to replace their Hierarchical File System (HFS) as the primary file system used on Macintosh computers. ...

With Mac OS X 10.2.3, Apple introduced Internet-Enabled Disk Images. With these images the contents of the disk image are automatically copied and the image file discarded.[1]

To open this kind of file in Windows, several programs such as Acute Systems TransMac, Daemon Tools, UltraISO or IsoBuster can be used.

See also

• Installer (Mac OS X)
• cloop, a similar disc image format designed for Linux LiveCDs
• Universal Disk Image Format (UDIF)

Installer is an application included in Mac OS X which extracts and installs files out of . ... The compressed loopback device or cloop is a module for the Linux kernel. ... Gnoppix 0. ... There are very few or no other articles that link to this one. ...

References

• Apple Developer Connection A Quick Look at PackageMaker and Installer
• O'Reilly Mac DevCenter Tip 16-5. Create a Disk Image from a Directory in the Terminal