Please be careful when running the following commands, as you might destroy important data or disk. How To Create Disk Image on Mac OS X With dd Command. The procedure is as follows: Open the Terminal app; Get disk list with the diskutil list; To create the disk image: dd if=/dev/DISK of=image.dd bs=512; To write the disk image: dd if=image.dd. A file extension format like DMG Apple Mac OS X Disk Image is a standard way that information is encoded for storage in a computer file. The file extension DMG Apple Mac OS X Disk Image format specifies how bits are used to encode information in a digital storage medium.
Disk Utility User Guide
You can restore a disk image to a disk. To do this, you first need to erase the disk. If the disk image has multiple partitions, you must restore each partition individually.
- Restore a disk image with multiple volumes to a disk. In the Finder on your Mac, double-click the disk image to open it. In the Disk Utility app, select the disk in the sidebar, click the Partition button, then partition the destination disk. In the sidebar, select the volume that you want to.
- The systematic steps to create a disk image of a drive using Disk Utility are as follows: Open Disk Utility and select the storage drive from the sidebar; Go to File New Image Image from “Drive Name” Give a name to your disk image file and provide a destination to save the file; Click the Format popup menu, then choose your required option.
- Dec 21, 2017 Create and Work With Disk Images. RELATED: How to Create an Encrypted Disk Image to Securely Store Sensitive Files on a Mac. Click the File menu in Disk Utility and use the New menu to create blank disk images or disk images containing the contents of a folder — these are.DMG files. You can then mount that disk image file and write files.
Restore a disk image with a single volume to a disk
- In the Disk Utility app on your Mac, select the volume that you want to restore in the sidebar, then click the Restore button .This is the volume that is erased and becomes the exact copy.
- Click the Restore pop-up menu, then choose the volume you want to copy.If you’re restoring from a disk image, click the Image button, then navigate to that disk image.
- Click Restore.
Restore a disk image with multiple volumes to a disk
To restore a disk image with multiple volumes to a disk, you must partition the destination disk, then restore each volume individually.
- In the Finder on your Mac, double-click the disk image to open it.The disk image’s volumes appear as disks in the Finder.
- In the Disk Utility app, select the disk in the sidebar, click the Partition button , then partition the destination disk.The destination disk must have as many partitions as the disk image, and each of the disk’s partitions must be at least as large as the corresponding partition in the disk image. See Partition a physical disk in Disk Utility on Mac.
- In the sidebar, select the volume that you want to restore, then click the Restore button .This is the volume that is erased and becomes the exact copy.
- Do one of the following:
- Restore from a volume: Click the “Restore from” pop-up menu, then choose the volume you want to copy.
- Restore from a disk image: Click Image, choose the disk image you want to copy, then click Open.
- Click Restore.
- Repeat steps 3–5 for each remaining partition.
See alsoCreate a disk image using Disk Utility on MacAdd a checksum to a disk image using Disk Utility on MacVerify that a disk image’s data isn’t corrupted using Disk Utility on Mac
The icon depicts an internal hard drive within a generic file icon. | |
Filename extension | |
---|---|
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) from Mac OS X and the New Disk Image Format (NDIF) from Mac OS 9. 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. Macbook pro 2012 os.
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. 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:
- 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]
- ^ 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.
- ^ ab'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.
- ^ ab'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.
- ^'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.
- ^'About TransMac for Windows'. www.acutesystems.com.
- ^'Convert'. www.winytips.com. winytips. Retrieved 5 May 2020.
- ^Olivia Dehaviland (2015-03-03). 'Apple DMG Disk Image Viewer'. DataForensics.org. Archived from the original on 2015-04-02. Retrieved 2015-03-10.
- ^'darling-dmg'. darling-dmg. Retrieved 29 March 2015.
External links[edit]
How To Create A Disk Image
- 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 Usb
Retrieved from 'https://en.wikipedia.org/w/index.php?title=Apple_Disk_Image&oldid=979643441'