Double-clicking dmg files not mounting on macOS Sequoia

Try this sequence:

On the old mac create a new folder on the desktop call it OLD.

On the old mac drag your .dmg files to this OLD folder.

On the new mac create a folder on the desktop and call it NEW

On the new mac create an appropriate sized .dmg like the size of the old one that is empty.

Now airdrop the files from the OLD folder to the NEW folder.

Once this is done, drag the files from the NEW folder to the empty .dmg on the new mac.

At this point you still have all of your files on both macs.

In the old mac you should have them in your .dmg as well as the OLD folder.

On the new mac you will have your files in the NEW folder and the .dmg

This has all to do with the fact that the .dmg is "a piece" of the hard drive as you can see in Disk Utility and for that "architectural" reason .dmg's can't be swapped.

Once you are hopefully successful, you can trash what is in the OLD and NEW folders as they would now be "living" in their respective .dmgs

What I describe is a workaround, which I have used.

Hope this helps

dancingpotato wrote:

Hello,

I was migrating some data I store in a password protected dmg file from an old macbook to a new one. Now I can't open the dmg file by just double clicking it!

I tried making a new dmg file on the new computer and copying data into it. This worked for a while, but then stopped working. I have multiple user accounts and have the dmg in a shared location between them. The account switching could be an issue.

What's weird is, so far I can always reliably mount the dmg file using the "hdiutil attach <dmg file>" command in the terminal. The simplicity of the terminal command is getting around whatever is broken. However, now I don't trust my system to reliably mount my dmg file when I need it. I'm considering switching to a third party solution to make file containers if I can't find an answer.

I'm wondering if this is a bug in the new Sequoia OS. At this point, I'm just hoping a future update will fix the issue.

Any idea what could be going on here?

[Re-Titled by Moderator]

I would file a bug report / submit your Apple Feedback here: Product Feedback - Apple

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The current stable release of Sequoia including bug fixes, security updates is macOS 15.2

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