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macos Majove cannot read disk from Big Sur

I have a disk from another machine that was running big sur. I went back to my box that has mojave. I attached the big sur drive to the mojave box and it says it cannot read the disk. It says unsupported format.


Is there a way to read it so I can copy files from it? Th update and data containers mount but not the main part of the disk. The data part of the disk is not readable. No perms. It has the red minus pic on the folders. I do not have access to the big sur box anymore.


I did try to use disk utility to mount all devices ;but the main part of the disk still does not mount.

Posted on Jan 19, 2021 12:48 PM

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Question marked as Top-ranking reply

Posted on Jan 20, 2021 4:56 AM

With the Big Sur disk connected to your Mojave mac,

make sure the Big Sur disks icon is displayed on the Desktop.


Highlight the Big Sur disk and press Command and i

this will bring up the info panel

at the bottom click on Sharing & Permissions.


Click the plus button and add your user name to the list,

make sure the permissions are set to Read & Write then

click the gear icon with the downward pointing arrow and click

on Apply to enclosed items.

After a few minutes the no entry sign will disappear from the folders.




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8 replies
Question marked as Top-ranking reply

Jan 20, 2021 4:56 AM in response to TRON3030

With the Big Sur disk connected to your Mojave mac,

make sure the Big Sur disks icon is displayed on the Desktop.


Highlight the Big Sur disk and press Command and i

this will bring up the info panel

at the bottom click on Sharing & Permissions.


Click the plus button and add your user name to the list,

make sure the permissions are set to Read & Write then

click the gear icon with the downward pointing arrow and click

on Apply to enclosed items.

After a few minutes the no entry sign will disappear from the folders.




macos Majove cannot read disk from Big Sur

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