Apple Disk Image

1. Apple Disk Image Mounter
2. Apple Disk Image Media

There are a half dozen Apple-II disk image formats and several toolsfor manipulating them. Scavenging the histories is a bit of work initself leading to parameters that no longer exist and formats that aredeprecated or superceded.

A quick run down on common Formats:

• DSK (.dsk, .do, .po). 5.25' DOS 3.3 or Prodos format
  • .dsk could be any disk image but for Apple it's usually one of .do or .po
  • .do is typically DOS 3.3, usually 16 sectors but occasionally 13 sectors
  • .po is Prodos format.
• HDV. 800k Prodos format.
• NIB. 'Nibble Copy' Used for copy protected disks. DOS 3.3 formatwith extra track and sector info.
• WOZ. An offshoot of the AppleSaucedisk controller project, the de facto standard for images ofcopy-protected disks.

Tools

Apple introduced a disk image format in the name of DMG file. DMG files are known as the proprietary disk image file for Apple that is used generally on Mac OS machines. Therefore, most users are in the habit of keeping image backup of their system data in the form of DMG files.

So I booted under Disk Utility and wiped the 'Internal Drive' by going to erase and setting the security options. But there is a drive under 'Disk Images' called 'Apple disk image Media' with 'OS X Base System' under it, using 1.27 GB with 728 MB free. Jan 13, 2019 Apple II Disk Image Collection includes many Apple II utilities including programming, sound, productivity, graphics, games, education, communications, and more. We tried to give a count of how many apps were included and gave up at over 5,000. Apple II fans will have countless hours of fun with these classic apps. Jul 06, 2019 This wikiHow teaches you how to open a disk image file (.img) on Windows or macOS. An.img file is exact image of a file system—you can either mount it as a drive or open it in an app like WinZip. This opens the Windows File.

AppleCommander

• written in Java
• CLI
• GUI native for each platform
• Very complete
  • create/modify disk images (.do, .dsk, .po, .nib, .2mg, .hdv) including gzipped ones
  • add/remove/export files
  • file viewing including some graphics formats and BASIC detokenizing
  • Shrinkit support
• GPL-2.0 License

This has been around for a while. Older documentation and several CC65threads refer to arguments and parameters that no longer exist,fortunately the change requestdiscussion is public.

CiderPress

• Windows
• GUI
• Swiss-army tool for files and disks
  • create and manipulate images (.2mg, .dsk, .img, .app. .hdv, .ddd, .po, .do, .raw, .nib)including gzipped
  • disassembler
  • file viewing including common graphics formats, format decoding, BASIC detokenizing
  • hex editor
  • Shrinkit support
• BSD License

DiskM8

• written in Go (Linux, OSX, and Windows)
• CLI
• Swiss-army command line tool for Apple disks.
  • create and manipulate ProDOS, DOS 3.x (.dsk, .po, .2mg, .nib)
  • extract and convert binary, text, and detokenize BASIC files
  • disk reports and comparison
• GPL-3.0 License

DSKalyzer

Mentioned in links, archived threads, and odd documentation this oneby the same group predated DiskM8. It hasn't been updated.

DiskBrowser

• Java
• GUI
• GPL-3.0 License

DiskBrowser is a Java-based GUI for exploring disk images. Unlike theothers it doesn't let you manipulate the images but it does decodetheir structure and lets you browse sector/block dump or disassemblyand to view a number of graphics and data formats. Neat. Much moreconvenient than using od and hand disassembly.

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) from Mac OS X and the New Disk Image Format (NDIF) from Mac OS 9. Music player software for mac. An Apple disk image file's name usually has '.dmg' as its extension.

Features[edit]

Apple Disk Image files are published with a MIME type of application/x-apple-diskimage.

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 multilingual 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', 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 (a spoonerism of FileVault).^[8]

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]

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.

Metadata[edit]

The UDIF metadata is found at the end of the disk image following the data. This trailer can be described using the following C structure.^[10] All values are big-endian (PowerPC byte ordering)

The XML plist contains a blkx (blocks) key, with information about how the preceding data fork is allocated. The main data is stored in a base64 block, using tables identified by the magic 'mish'. This 'mish' structure contains a table about blocks of data and the position and lengths of each 'chunk' (usually only one chunk, but compression will create more).^[10] The data and resource fork information is probably inherited from NDIF.

Encryption[edit]

The encryption layer comes in two versions. Use apple watch to unlock mac. Version 1 has a trailer at the end of the file, while version 2 (default since OS X 10.5) puts it at the beginning. Whether the encryption is a layer outside of or inside of the blkx metadata (UDIF) is unclear from reverse engineered documentation, but judging from the vfcrack demonstration it's probably outside.^[8]

Utilities[edit]

There are few options available to extract files or mount the proprietary Apple Disk Image format. Some cross-platform conversion utilities are: Apple hard disk 2tb.

• dmg2img was originally written in Perl; however, the Perl version is no longer maintained, and the project was rewritten in C. It extracts the raw disk image from a DMG, without handling the file system inside. UDIF ADC-compressed images (UDCO) 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]
• The Sleuth Kit. Handles the DMG format, HFS+, and APFS.

Most dmg files are unencrypted. Because the dmg metadata is found in the end, a program not understanding dmg files can nevertheless read it as if it was a normal disk image, as long as there is support for the file system inside. Tools with this sort of capacity include:

• Cross-platform: 7-zip (HFS/HFS+), PeaZip (HFS/HFS+).
• Windows: UltraISO, IsoBuster, MacDrive (HFS/HFS+).^[13]
• Unix-like: cdrecord and mount (e.g. mount -o loop,ro -t hfsplus imagefile.dmg /mnt/mountpoint).^[14][15]

Tools with specific dmg support include:

• Windows:
  • Transmac can handle both UDIF dmgs and sparsebundles, as well as HFS/HFS+ and APFS. It is unknown whether it handles encryption.^[16] It can be used to create bootable macOS installers under Windows.^[17]
  • A free Apple DMG Disk Image Viewer also exists, but it is unknown how much what it actually supports.^[18]
• Unix-like:
  • darling-dmg is a FUSE module enabling easy DMG file mounting on Linux. It supports UDIF and HFS/HFS+.^[19]

See also[edit]

References[edit]

Apple Disk Image Mounter

1. ^ ^abcdefg'hdiutil(1) Mac OS X Manual Page'. Archived from the original on 2016-05-14. Retrieved 2016-05-14.
2. ^ ^ab'Mac OS X: Using Disk Copy disk image files'. Archived from the original on 2013-12-19. Retrieved 2013-04-25.
3. ^hdiutil(1) – Darwin and macOS General Commands Manual
4. ^'Re: Some apps refuse to launch in 10.2.8! (OT, but very important)'. Archived from the original on 2014-01-17.
5. ^'Guides'. Apple. Archived from the original on 2009-03-06. Retrieved 2010-10-27.
6. ^'DART 1.5.3: Version Change History'. Archived from the original on 2013-12-19. Retrieved 2013-04-25.
7. ^'Software Downloads: Formats and Common Error Messages'. Archived from the original on 2010-12-24. Retrieved 2009-05-06.
8. ^ ^ab'VileFault'. 2006-12-29. Archived from the original on 2007-01-09. Retrieved 2010-10-27.
9. ^Michael Tsai (2015-10-07). 'LZFSE Disk Images in El Capitan'. Archived from the original on 2017-04-09. Retrieved 2017-04-09.
10. ^ ^ab'Demystifying the DMG File Format'. Archived from the original on 2013-03-17.
11. ^'dmg2img'. Archived from the original on 29 November 2010. Retrieved 2010-10-27.
12. ^'DMGExtractor'. Archived from the original on 2011-01-02. Retrieved 2011-01-03.
13. ^MacDrive Features / Boot Camp / System Requirements /. 'MacDrive Home page'. Mediafour. Archived from the original on 4 October 2010. Retrieved 2010-10-27.
14. ^'How To Convert DMG To ISO in Windows, Linux & Mac'. Archived from the original on 2010-03-07.
15. ^'Convert DMG To ISO using PowerISO'. Archived from the original on 2009-05-02. Retrieved 2009-02-15.
16. ^'About TransMac for Windows'. www.acutesystems.com.
17. ^'Convert'. www.winytips.com. winytips. Retrieved 5 May 2020.
18. ^Olivia Dehaviland (2015-03-03). 'Apple DMG Disk Image Viewer'. DataForensics.org. Archived from the original on 2015-04-02. Retrieved 2015-03-10.
19. ^'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

Apple Disk Image Media