Dmg Not Opening On My Mac

If you can’t open Safari or a new Safari window, try these suggestions. Make sure you’re using the latest versions of Safari and macOS. To check for a Safari or a macOS update, choose Apple menu App Store, then click Updates. Nov 08, 2019  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. MacOS Sierra (10.12) and earlier is not able to mount the new Apple File System (APFS).

Rated (3.9 of 5.0) by 7 reviewers.
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.

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:

  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.

Dmg not opening on my mac account

This article explains how to download and install Firefox on a Mac.

  • If you are updating from a previous version of Firefox, see Update Firefox to the latest release.
Note: This article only applies to Mac. For instructions to install Firefox on Windows, see How to download and install Firefox on Windows.For instructions to install Firefox on Linux, see Install Firefox on Linux.
Make sure your Mac meets the System Requirements for Firefox. If you use an old version of OS X, see this article for more information:
  1. Visit the Firefox download page in any browser (for example, Apple Safari). It will automatically detect the platform and language on your computer and recommend the best version of Firefox for you.
  2. Click the download button to download Firefox.
    • Note: If you want to have a choice of the language for your Firefox installation, select the 'Download in another language' link under the download button instead.
  3. Once the download has completed, the file (Firefox.dmg) should open by itself and pop open a Finder window containing the Firefox application. Drag the Firefox Icon on top of the Applications folder in order to copy it there.
    Note: If you do not see this window, double-click the Firefox.dmg file that you downloaded to open it.
  4. After dragging Firefox to the Applications folder, hold down the control key while clicking in the window and select Eject 'Firefox' from the menu.

Mac Dmg File Download

Complete the steps above before running Firefox. Do not run Firefox directly from the Firefox.dmg file, as this can result in issues such as lost data and settings.

Tip: You can add Firefox to your dock for easy access. Just open your Applications folder and drag Firefox to the dock.

Firefox is now ready for use. Just click on its icon in the dock or Applications folder to start it.

When you first start up Firefox, you will be warned that you downloaded Firefox from the Internet. Because you download Firefox from the official site, you can click .

Install Dmg On Mac

Upon installation, Firefox will not be your default browser, which you'll be notified about. That means that when you open a link in your mail application, an Internet shortcut, or HTML document, it will not open in Firefox. If you want Firefox to do those things, click to set it as your default browser. If you're just trying out Firefox or simply do not wish to set Firefox as your default browser, click .