Disk Image Dmg Loads Blank

Posted By admin On 24.05.21

Mar 03, 2018 Open Disk Utility in the Utilities' folder. After Disk Utility loads select the drive (out-dented entry with the mfg.' S ID and size) from the side list. Click on the Erase tab in the Disk Utility toolbar. Name the drive, 'MyVolume'.

The instructions below are specific to the Disk Utility program available on the Mac OSX Operating System on the Macintosh computers in IT Computer Classrooms. Even if your computer has a different version of Mac OS X, these instructions should provide a general guide for completing this process. Refer to the documentation provided with your Mac operating system software if you need more specific information.

Burn a DMG or ISO File to Disk

After you have downloaded a program's installation file (*.dmg format for a Mac-compatible program, *.iso format for a Windows-compatible program) to a Macintosh computer's hard drive, you can burn this *.dmg or *.iso file to a blank CD or DVD. You can use this disk to install the program on another computer, or have a backup installation disk in case you need to reinstall the program in the future. You can use a Mac to burn an *.iso file to a disk, and the resulting installation disk will run properly on a Windows computer.

Note: For .dmg or .iso files that are larger than 4.7 GB, you will need to use dual layer DVD. See About Recordable Media Types for more information about different types of recordable DVDs.

To burn a DMG or ISO File to disk:

Start Applications > Utilities > Disk Utility. The Disk Utility window will open. The Mac's available drives (e.g., hard drive partitions, CD/DVD drive) will be listed by name in the left pane.
Insert a blank CD or DVD disc into the Mac CD/DVD drive. Note: If the CD is blank, the You inserted a blank CD pop-up window will appear. Select Action > Open Disk Utility, then click OK. The Disk Utility (a.k.a. SuperDrive) window will reappear.
Drag the *.dmg or *.iso file from a Finder window or the desktop to the Disk Utility window, and drop it in the left pane in the empty area below the Mac drive names. The *.dmg or *.iso file name will display in the left pane of the Disk Utility.
Note: You can drag and drop multiple files to the Disk Utility.
Select the *.dmg or *.iso name in the left pane of the Disk Utility, then click Burn (top left). The Burn Disc In: window will open and display the destination (your blank CD/DVD) for your file.
In the Burn Disc In: window, click Burn. The Disk Utility Progress window will open and the burning process will begin.
When the burning is complete, the disk is ejected from the drive and the Disk Utility Progress window displays a message that the image burned successfully. Click OK. The Disk Utility Progress window will close.

You can now close the Disk Utility and use your installation disk.

About Recordable Media Types

There are two types of recordable CDs and DVDs: CDs and DVDs labeled 'R' can only be recorded on once, while those labeled 'RW' allow you to write data to them once and then add more files later. You can also erase the data on CD-RW or DVD-RW disks entirely and re-use them, which you can't do with DVD/CD-Rs. You can use either kind in IT Computer Classrooms.

For dmg or *.iso files that are larger than 4.7 GB, you will need to use dual layer DVD.

Apple Disk Image
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 com.apple.disk-image-smi`
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.

Burn Dmg Image

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.

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 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).

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.

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]

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]