13-05-2021

Dmg File Won't Open In Mac

Nov 27, 2013  The Porting Team → Porting Section → Ask for help! → Help Me I'm New. There are a couple of options that may resolve this prior to Apple releasing 10.13.1: 1) Try restarting your mac, and trying to open the.DMG again. 2) Hold down the Control key when you click on the.dmg then select Open from the context menu. Theis should give you a window to 'allow anyway'. Oct 16, 2016 macOS should read these files and you should be able to open them fine with no issues, so I would suggest doing a fresh restart of your computer to see if that helps. If you still have an issue after that, try a backup of your Mac's important data and a reinstall of macOS using the following articles: Use Time Machine to back up or restore your Mac.

File type: Mac OS X Disk Image

Open DMG File

The usage of the DMG file extension is in the context of a mountable disk image file which is generated by the Mac OS X Operating System platform. Once the file is opened, the system will mount it in a virtual disk located on the user's desktop.

This type of file is normally utilized for the distribution of software installation packages for the Macintosh computer system.

Prior to the introduction of this file format, the Mac environment utilized the IMG up until the introduction of the Mac OS 9. 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. Basically, the DMG file extension can be compared to the EXE or ISO format of Windows and can even function as a complete virtual drive for the system.

The mimicking of physical CD drives is a workaround implemented by the system to address problems that may arise from CD requirements of some software programs including support for the efficient usage of an organization's resources.

File Extension Dmg

Detailed information

File format: Proprietary
Open with Windows: Acute Systems TransMac, DMG2IMG or DMG2ISO
The DMG format file is also used by video games distributed for the Macintosh computer environment which are commonly protection enabled.
This format makes sure that all software installation and execution in the system are carried out correctly by providing support for both physical and virtual drives required by the system.
Dmg File Won
Running an application from a virtual drive may also allow a user to execute a program without actually copying an instance of it in the physical storage drive of the computer system.
Dmg
This will save storage space and proves to be advantageous especially for programs which are not used very often. Aside from the Apple tool bundled with the Operating System, other more commonly used utilities that serve as an alternative include MagicISO, IsoBuster, and UltraISO.
These programs are more popularly executed under the Windows environment but are capable of reading DMG file formats and compressing them into another file extension that is more popularly used.
Another example of this conversion program is the DMG2ISO.

Dmg File Open In Mac

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Kelly Heffner Wilkerson
November 8, 2019 at 6:30 AM
Categories: macOS | View Comments


I ran into an interesting macOS error while working with a customer a couple of weeks ago. I didn't find a lot of good search results addressing the issue, so I decided to write up a post about it myself.

Dmg File Won't Open In Mac 2017

The error was as the screenshot above shows; trying to open a dmg (disk image), macOS showed the error 'no mountable file systems'. If you see the 'no mountable file systems error' while opening a dmg, here's what you should try:

Dmg File Won't Open In Mac Os

  1. In most cases, the downloaded dmg file is actually corrupt or had an error downloading. If possible, try downloading the dmg again, turning off any download assistant plug-ins you may have. You can try downloading the file in a different browser as well. Or if you don't need to be logged in to the site to download the file and you want to be fancy, you can try curl -O url in Terminal to download the file. (There's an example of that in my screenshot below.)

  2. Reboot your Mac if you haven't already tried that. Apparently there is an issue sometimes after opening too many dmg files, that is fixed with a reboot.

  3. Try mounting the DMG on the command line in Terminal. We will at least get some sort of useful error message to go on if it still fails:

    • Open Terminal: In Spotlight, the search magnifying glass at the upper right corner of your screen, search for Terminal, and press enter to open the Terminal app.

    • Type hdiutil attach -verbose into the terminal. Add a space at the end, but don't press enter yet.

    • Drag the dmg file from your Finder window onto the Terminal window and let go. This will fill in the location of the dmg file into your Terminal window.

    • Press enter.

  4. macOS Sierra (10.12) and earlier is not able to mount the new Apple File System (APFS). So if you're on macOS Sierra (10.12) or earlier and you ran hdiutil and see references to Apple_APFS or error 112, the issue is likely legitimate incompatibility, and this disk image won't open on this Mac without an update to the operating system.

    Here's an example of the end of hdiutil attach -verbose output that shows an APFS error due to an older version of macOS:

  5. Think about if you have any kind of security policies on this machine to prevent writing to external drives (thumb drives, optical drives, etc). I haven't seen this one in action, but I read about this being a possibility while researching the issue.

  6. Another suggestion added by a reader (thank you, Markus!) is that filesystem errors on your main Mac drive could be the cause of the disk image mounting errors. Here are instructions from Apple for scanning and repairing errors using Disk Utility. Note that in order to scan and repair errors on your main Macintosh HD drive, you'll need to reboot your Mac into recovery mode. You'll want to choose Disk Utility in the utilities listed in the recovery mode menu.

  7. A new discovery from a reader (thank you, Colby!) is that APFS DMGs won't mount if you're booted in macOS booted in Safe Mode. (Who knew!?!) If you're not sure if you're in safe mode, select the Apple menu  > About This Mac > System Report button, then select the 'Software' heading from the left column. To exit safe mode, restart your Mac, without holding Shift during startup. Or, if you previously set your Mac to always boot into safe mode using nvram, turn off safe mode and have your Mac boot normally on the terminal:

    • Open Terminal: In Spotlight, the search magnifying glass at the upper right corner of your screen, search for Terminal, and press enter to open the Terminal app.

    • Type/paste sudo nvram boot-args=' and press enter.

    • Restart your Mac.