Encrypted disk image won't mount

[mac_in_tosh]

I'm on Big Sur 11.6.2. I've had an encrypted disk image on my desktop for many years. Today, when I double-clicked on it and entered the password a Warning window popped up saying the disk image couldn't be opened because "no mountable file systems." I copied the disk image over to an older Mac running High Sierra and it opened fine. It is formatted as APFS. What's this about and what can I do? Thanks.

 

[chown33]

I suggest making a duplicate of the disk image, then running Disk Utility's First Aid on the duplicate. If it detects any problems with either the whole device, or any volumes on it, then post what the errors are.

 

[mac_in_tosh]

I suggest making a duplicate of the disk image, then running Disk Utility's First Aid on the duplicate.

But neither the original nor the duplicate show up in Disk Utility.

I have an encrypted external USB drive. It mounts as expected on the Big Sur machine.

 

[mac_in_tosh]

Just tried it again after a shut down and restart of the computer and the desktop encrypted drive is now opening as expected.

 

[mac_in_tosh]

Now it's not opening again and with the same error message. I had made no changes to the disk image since the last time when it opened. I logged out of the account and logged back in but that didn't help. I don't want to do a restart right now. Any suggestions?

 

[Fishrrman]

"Any suggestions?"

My suggestion:
(there he goes again, just like a broken record...)

STOP USING encrypted disk images.

Put the data onto an unencrypted drive.
Or... even protect the drive with a password.

Keep it locked up when not in use if the data on it is that sensitive.

You want to be able to "get at" your data when you need it.

 

[BrianBaughn]

This recent thread may help:

Can't mount encrypted disk images after Monterey upgrade

I have some encrypted disk images I've been using since 2007 to store health, financial records, etc.. and I can't open them since I moved to macOS 12. I waited until 12.1 avoid some of these bugs. I just get a message "The disk image couldn't be opened - The disk image is corrupted" when I...

forums.macrumors.com

 

[mac_in_tosh]

STOP USING encrypted disk images.

Put the data onto an unencrypted drive.

The encrypted disk image is just a convenience for temporary things that are not of utmost sensitivity and of no great consequence if lost. I get what you are saying, but still a desktop disk image should open up.

 

[mac_in_tosh]

Some further observations.

After confirming that the desktop disk image won't open with the same error message, I dragged it to an external (unencrypted) USB drive. It opened there. I deleted the image from the desktop and dragged the one on the USB drive to the desktop. It then opened on the desktop.

So any idea what's going on?

Edited: a few minutes later when I went back to the account where the disk image is on the desktop it again wouldn't open.

 

[mac_in_tosh]

Not sure if anyone is following this thread, but here's the latest:

I created a new encrypted disk image on the desktop but this time formatted as Mac OS Extended (Journaled) instead of the previous APFS. So far with several attempts on separate days the disk image has opened as expected.