Fix the error "No mountable file systems" on Mac

By Connie | Posted to Home > Howto, on October 18th, 2021

Summary: Help you fix the macOS error "The following disk images couldn't be opened. No mountable file systems." with efficient solutions. Then, you can mount and open the DMG file again.

Fix the error - no mountable systems on Mac

Usually, when you double-click a DMG (Disk Image) file, it will mount and open automatically. However, the target DMG file doesn't open this time but pops up an error message like the following:

The following disk images couldn't be opened. No mountable file systems.

DMG file 'no mountable file systems' error on Mac

As the error message indicates, the disk image cannot be mounted. So, how can you open the DMG and access files stored on it?

You are in the right place. This article will show you the best solutions to fix the "No mountable file systems" error. And then, you can read-write all data on it. Let's explore more together.

Solutions for fixing "No mountable file systems" on Mac:

How to fix the error "No mountable file systems"?

The causes of the error vary as there are different scenarios. So, there are several solutions for resolving the problem. You can troubleshoot this error by trying the ways below one by one.

Solution 1: Download the DMG file once again

Most of the time, this error shows that the DMG file is already corrupt or corrupt by your wrong operation during downloading.

So, you can try to download it again with all the download assistant plug-ins off. If the newly downloaded DMG file still cannot be opened, try downloading it from another browser.

Or, you can directly download the DMG file via using Terminal.

  • Open Finder > Applications > Utilities > Terminal.
  • Enter the following command in Terminal. Here, you should replace url with the DMG download URL. Then, press Return / Enter.
  • curl -O url
  • Download DMG file via command

Note: To check the DMG download URL, right-click it in Finder and click Get Info > More Info > Where from.

Solution 2: Restart your Mac

Sometimes, the Mac OS detects the DMG file but fails to recognize its format. So, it feedbacks you the error message "No mountable file systems" when you clicking the DMG.

You can try to reboot your Mac to check if it is just caused by the temporary bug of your operating system.

Solution 3: Check the file system of the DMG

The Disk Image is a type of virtual drive. It is also formatted with a file system before storing data. If the format of the downloaded DMG is not compatible with your Mac, it can't be mounted.

Usually, Mac OS is only compatible with APFS, HFS+, exFAT, and FAT32/16 while read-only on NTFS drives. Besides, macOS Sierra (10.12) and earlier don't support APFS.

You can download the DMG on a Windows PC to see if it can be opened. If yes, the DMG maybe only Windows-compatible. And if your Mac runs macOS 10.12 or earlier, you can upgrade your macOS version to check if the error can be fixed.

Solution 4: Mount the DMG in Terminal

If the above simple tricks can't help you mount and open the Disk Image, you can try to mount it using the command in Terminal.

Here's how to mount the DMG in Terminal:

  • Search for Terminal in the Spotlight Search box at the upper right corner of your screen. Double-click Terminal in the recommended results to open it.
  • Open Terminal from Spotlight
  • Type the following command in Terminal and add a space. Don't press Return / Enter at this time.
  • hdiutil attach -verbose
  • Drag the DMG file from your Finder onto the Terminal window to fill in the location of the DMG file into your Terminal.

Mount the DMG file in Terminal

Now, you can check whether the DMG file shows up on your desktop or Finder. If it is, the DMG file is mounted successfully.

Moreover, some users even find that the security policies they set will make the DMG file can't be mounted on Mac. Therefore, you can also check your security settings to enable the DMG mountable on your Mac.

Why does the "No mountable file systems" error occur on Mac?

The unmountable issue of Disk Images is just like that of hard drives, which is also related to the OS and the file format.

When a Disk Image is not mounted on your Mac, the most common reasons are as below:

  1. The DMG file is already corrupt.
  2. The format of the DMG file is corrupt or not compatible with your Mac OS.
  3. Some bugs that pop up during the operating system recognizing the DMG file.


The macOS error "The following disk images couldn't be opened. No mountable file systems." is very common in daily life. When you run into this problem, it doesn't mean that you can't access the DMG files anymore.

The fixes mentioned in this post are testified useful for resolving the issue. You can follow them one by one to make your unmounted DMG file accessible again. Hope you this article will help you out the trouble.

Also like:

Cannot Mount External Hard Drive on Mac, How to Fix?


1. What is a DMG file?

An Apple Disk Image (DMG) often refers to the file format used to store compressed software installers instead of a need for a physical disk. When a DMG opened, it also mounted as a volume in Finder and Disk Utility.

2. How do you open a DMG file on Mac?

Usually, when you double-click the DMG file in Finder, it will mount and open automatically. Then, you can access files or software installers stored on it.