Dec 03, 2003 A dmg is a disk image. I think of them as a disk within a disk. If it won't mount it's possible the file is corrupted, or incomplete. Also I think there is a way to not automatically verify dmg files, which will sometimes let you mount dmg's with 'weird behaviors'. I could be wrong about that one though. Macs 'don't do' executable files.
- The Apple Disk Utility is the main application associated by users to this particular file type under the Macintosh platform and is bundled with the Mac OS X installation package. Although not meant to be directly opened under the Microsoft Windows Operating System platform, the DMG format file can be accessed by Windows users by using some third party applications in the market.
- Oct 17, 2019 A DMG file (.dmg) is a Mac OS X Disk Image file and it is used to package files or folders providing compression, encryption, and read-only to the package. ##Creating the DMG file #Disk Utility Type Disk Utility into Spotlite CMD+SPACEBAR from Finder or from Terminal.
The icon represents an internal hard drive within a generic file icon. | |
Filename extension | .dmg, .smi, .img |
---|---|
Internet media type | application/x-apple-diskimage |
Uniform Type Identifier (UTI) | com.apple.disk-image |
Developed by | Apple Inc. |
Type of format | Disk image |
Apple Disk Image is a disk image format commonly used by the macOS operating system. When opened, an Apple Disk Image is mounted as a volume within the Macintosh Finder.
An Apple Disk Image can be structured according to one of several proprietary disk image formats, including the Universal Disk Image Format (UDIF) and the New Disk Image Format (NDIF). An Apple disk image file's name usually has '.dmg' as its extension.
- 3File format
Features[edit]
Apple Disk Image files are published with a MIME type of application/x-apple-diskimage.
Download from netflix mac. Different file systems can be contained inside these disk images, and there is also support for creating hybrid optical media images that contain multiple file systems.[1] Some of the file systems supported include Hierarchical File System (HFS), HFS Plus, File Allocation Table (FAT), ISO9660 and Universal Disk Format (UDF).[1][2]
Apple Disk Images can be created using utilities bundled with Mac OS X, specifically Disk Copy in Mac OS X v10.2 and earlier and Disk Utility in Mac OS X v10.3 and later. These utilities can also use Apple disk image files as images for burning CDs and DVDs. Disk image files may also be managed via the command line interface using the hdiutil utility.[3]
In Mac OS X v10.2.3, Apple introduced Compressed Disk Images[4] and Internet-Enabled Disk Images for use with the Apple utility Disk Copy, which was later integrated into Disk Utility in 10.3. The Disk Copy application had the ability to display a multi-lingual software license agreement before mounting a disk image. The image will not be mounted unless the user indicates agreement with the license.[5]
An Apple Disk Image allows secure password protection as well as file compression, and hence serves both security and file distribution functions; such a disk image is most commonly used to distribute software over the Internet.
History[edit]
Apple originally created its disk image formats because the resource fork used by Mac applications could not easily be transferred over mixed networks such as those that make up the Internet. Even as the use of resource forks declined with Mac OS X, disk images remained the standard software distribution format. Disk images allow the distributor to control the Finder's presentation of the window, which is commonly used to instruct the user to copy the application to the correct folder.
A previous version of the format, intended only for floppy disk images, is usually referred to as 'Disk Copy 4.2' format, after the version of the Disk Copy utility that was used to handle these images.[1] A similar format that supported compression of floppy disk images is called DART.[1][6]
New Disk Image Format (NDIF) was the previous default disk image format in Mac OS 9,[1] and disk images with this format generally have a .img (not to be confused with raw .img disk image files) or .smi file extension. Files with the .smi extension are actually applications that mount an embedded disk image, thus a 'Self Mounting Image', and are intended only for Mac OS 9 and earlier.[7][2]
Universal Disk Image Format (UDIF) is the native disk image format for Mac OS X. Disk images in this format typically have a .dmg extension.[1]
File format[edit]
Apple has not released any documentation on the format, but attempts to reverse engineer parts of the format have been successful. The encrypted layer was reverse engineered in an implementation called VileFault[8] (a spoonerism of FileVault). Free mac adware cleaner.
Apple disk image files are essentially raw disk images (i.e. contain block data) with some added metadata, optionally with one or two layers applied that provide compression and encryption. In hdiutil these layers are called CUDIFEncoding and CEncryptedEncoding.[1]
How To Install Dmg File
https://occuqn.weebly.com/dd-5e-guns-dmg.html. UDIF supports ADC (an old proprietary compression format by Apple), zlib, bzip2 (as of Mac OS X v10.4), and LZFSE (as of Mac OS X v10.11)[9] compression internally.
Trailer[edit]
The trailer can be described using the following C structure.[10] All values are big-endian (PowerPC byte ordering)
Here is an explanation:
Position(in Hex) | Length (in bytes) | Description |
---|---|---|
000 | 4 | Magic bytes ('koly'). |
004 | 4 | File version (current is 4) |
008 | 4 | The length of this header, in bytes. Should be 512. |
00C | 4 | Flags. |
010 | 8 | Unknown. |
018 | 8 | Data fork offset (usually 0, beginning of file) |
020 | 8 | Size of data fork (usually up to the XMLOffset, below) |
028 | 8 | Resource fork offset, if any |
030 | 8 | Resource fork length, if any |
038 | 4 | Segment number. Usually 1, may be 0 |
03C | 4 | Segment count. Usually 1, may be 0 |
040 | 16 | 128-bit GUID identifier of segment |
050 | 4 | Data fork checksum type |
054 | 4 | Data fork checksum size |
058 | 128 | Data fork checksum |
0D8 | 8 | Offset of XML property list in DMG, from beginning |
0E0 | 8 | Length of XML property list |
0E8 | 120 | Reserved bytes |
160 | 4 | Master checksum type |
164 | 4 | Master checksum size |
168 | 128 | Master checksum |
1E8 | 4 | Unknown, commonly 1 |
1EC | 8 | Size of DMG when expanded, in sectors |
1F4 | 12 | Reserved bytes (zeroes) |
Utilities[edit]
There are few options available to extract files or mount the proprietary Apple Disk Image format. Some cross-platform conversion utilities are:
- dmg2img was originally written in Perl; however, the Perl version is no longer maintained, and the project was rewritten in C. Currently, without additional tools, the resulting images may be mounted only under Mac OS X and under Linux (provided hfsplus support has been enabled). UDIF ADC-compressed images have been supported since version 1.5.[11]
- DMGEXtractor is written in Java with GUI, and it supports more advanced features of dmg including AES-128 encrypted images but not UDCO images.[12]
- 7-Zip, including the free cross-platform port of its command-line interface, p7zip.
In Windows, most dmg images can be opened using several other programs such as UltraISO and IsoBuster. MacDrive can also mount simple dmg files as drives under windows, but not sparse disk or encrypted dmgs.[13] A free Apple DMG Disk Image Viewer also exists.[14]
![File File](/uploads/1/3/4/3/134367521/521831568.jpg)
In Linux and possibly other Unix flavors, most .dmg files can be burned to CD/DVD using any CD-burner program (using cdrecord directly or a front-end such as K3B or Brasero) or directly mounted to a mountpoint (e.g.
mount -o loop,ro -t hfsplus imagefile.dmg /mnt/mountpoint
).[15][16] darling-dmg is a FUSE module enabling easy DMG file mounting on Linux.[17]See also[edit]
References[edit]
- ^ abcdefg'hdiutil(1) Mac OS X Manual Page'. Archived from the original on 2016-05-14. Retrieved 2016-05-14.
- ^ ab'Mac OS X: Using Disk Copy disk image files'. Archived from the original on 2013-12-19. Retrieved 2013-04-25.
- ^
hdiutil(1)
– Darwin and macOS General Commands Manual - ^'Re: Some apps refuse to launch in 10.2.8! (OT, but very important)'. Archived from the original on 2014-01-17.
- ^'Guides'. Apple. Archived from the original on 2009-03-06. Retrieved 2010-10-27.
- ^'DART 1.5.3: Version Change History'. Archived from the original on 2013-12-19. Retrieved 2013-04-25.
- ^'Software Downloads: Formats and Common Error Messages'. Archived from the original on 2010-12-24. Retrieved 2009-05-06.
- ^'VileFault'. 2006-12-29. Archived from the original on 2007-01-09. Retrieved 2010-10-27.
- ^Michael Tsai (2015-10-07). 'LZFSE Disk Images in El Capitan'. Archived from the original on 2017-04-09. Retrieved 2017-04-09.
- ^'Demystifying the DMG File Format'. Archived from the original on 2013-03-17.
- ^'dmg2img'. Archived from the original on 29 November 2010. Retrieved 2010-10-27.
- ^'DMGExtractor'. Archived from the original on 2011-01-02. Retrieved 2011-01-03.
- ^MacDrive Features / Boot Camp / System Requirements /. 'MacDrive Home page'. Mediafour. Archived from the original on 4 October 2010. Retrieved 2010-10-27.
- ^Olivia Dehaviland (2015-03-03). 'Apple DMG Disk Image Viewer'. DataForensics.org. Archived from the original on 2015-04-02. Retrieved 2015-03-10.
- ^'How To Convert DMG To ISO in Windows, Linux & Mac'. Archived from the original on 2010-03-07.
- ^'Convert DMG To ISO using PowerISO'. Archived from the original on 2009-05-02. Retrieved 2009-02-15.
- ^'darling-dmg'. darling-dmg. Retrieved 29 March 2015.
External links[edit]
- 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
Retrieved from 'https://en.wikipedia.org/w/index.php?title=Apple_Disk_Image&oldid=917998972'
HomeHow to TipsWhat is DMG File And How to Open It
In computing world, DMG or (Disk Image File) is a file extension that belongs to Mac OS X. DMG file can also be termed as Apple Disk Image. The icon used equivalent to this file is an Internal Hard-drive. Disk Images are generally used worldwide in-order to distribute applications and software across the Internet. DMG file provides some attractive features that allow securing password along with file compression.
These virtual or physical Apple disks can be cloned from one to another. This is one of the powerful features of Mac.
These virtual or physical Apple disks can be cloned from one to another. This is one of the powerful features of Mac.
Tip: If you want to open and view DMG files of Apple Mac OS X so, you can try DMG Viewer tool.
Why DMG Files Are Created?
Earlier, Mac applications made use of Resource fork. These are the part of file system on Mac Operating System, which consists of both the structured data and non-structured data. Mac could not transfer these Resource forks over the mixed networks. Hence, the usage of Resource fork dwindled and this was the reason that Apple created disk image formats(DMG). The Resource forks are very important as they contain Meta data regarding the file.
Mounting and Dismounting on Mac OS
It is equivalent to plugging in a removable drive, where E drive is automatically created and while removing one chooses ‘Safely Remove Device’. Similarly, you have to eject the Mac drive for both the virtual and physical.
Two Disk Formats supported are:
Two Disk Formats supported are:
- NDIF
This was previously used as the default format of Mac, also known as New Disk Format. These files generally have an .img file extension. - UDIF
The native disk format of Apple Mac DMG file is UDIF (Universal Disk Image Format) with a file extension of .dmg.
MIME Type of DMG File:
application/x-apple-diskimage.
application/x-apple-diskimage.
Supported File Systems
Burn .dmg File
- Hierarchical File System (HFS) – This was developed by Apple Inc. for the systems supporting Mac OS. Earlier, these file systems were used in floppy disks and hard disks but later were used to read CD-ROM as well. It is known as Mac OS Standard.
- HFS Plus – It was developed after HFS, which is an extension of the same. It is known as Mac OS Extended.
- File Allocation Table (FAT) – It is a file system generally compatible with all file systems and helps in exchange of data between systems.
- ISO9960 – This is also a file system which was issued by ISO (International Organization for Standard) supporting various OS and helps in exchange of data.
- Universal Disk Format –This is a file system usually used to store broadcast media like DVD and optical disk formats.
How to Open DMG Files?
In Mac:
- When you download a Disk image, all the applications in it must be copied to the Application files, because many of these files will be in read-only format. Running these files inside the drives may produce some erroneous results.
- Double clicking the DMG File will open the file and you can view the contents in it. It might be images, documents, programs, etc.
- The DMG File consists of an application file. You can simply drag and drop to install them. If there is a possibility of having an installer, you can run these files instead of installing.
- Right-click on the File >> “Eject” (click on virtual disk instead of, original file)
Delete the old DMG Files after installing. The reason is old files may take more space when we install new programs.
Resize DMG Files
- Right click DMG File >> Click Get Info (View the original size).
- Open Disk Utility >>Select Images Tab>Click on Resize>>Select the DMG file to be resized.
- Click on Open >>Type the file size to be reduced>>Select Resize>>Done
In Windows:
Originally, DMG files are the default Disk Image file for Mac. Hence, they can be opened only on Mac OS.
Since there are no manual methods available to view the DMG Files in Windows, users can install external third-party software available online on Internet. DMG Viewer is one of the tools from such category.
The software provides you with the following features:
Originally, DMG files are the default Disk Image file for Mac. Hence, they can be opened only on Mac OS.
Since there are no manual methods available to view the DMG Files in Windows, users can install external third-party software available online on Internet. DMG Viewer is one of the tools from such category.
The software provides you with the following features:
Opening .dmg File
- Open DMG File in Windows OS based machine
- Read: Corrupt, Password Protected & Encrypted DMG
- Recover permanently deleted files from DMG
- Search a specific file type in large DMG Format Files
Conclusion
What Is A Dmg File Mac Os
Considering the ongoing necessity to view DMG files, we have described a manual process to let the users understand how to open & view DMG files. Else, users can take the help of a reliable third-party tool named as DMG Viewer. It is the best application that helps to read .dmg files in Windows OS. Users can use any approach as per their choice.