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User profile for user: XSemperIdem5
XSemperIdem5 Author
User level: Level 1
20 points

External drive not mounting after upgrading from Lion to El Capitan

I recently upgraded my early 2011 MBP from Lion to El Capitan (to then proceed to High Sierra). I set up a Seagate external drive as my Time Machine drive and the backup went smoothly under Lion. But now in El Capitan (10.11.16) the external drive won't mount. I can see it's connected as a USB device through System Information but it won't actually mount. I've tried restarting, powering off and back on, both with the drive connected and connecting it after logging in. The issue is the same under SafeBoot. Already did SMC reset and PRAM reset. Nothing helps. I don't have another computer to check the drive but it was perfectly fine right before.

Any ideas on what else I can try next? I need to backup before I can proceed with upgrading to High Sierra.

MacBook Pro 13″, OS X 10.11

Posted on Apr 6, 2022 5:51 PM

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3 replies
User profile for user: Lissy_12
Lissy_12
User level: Community Specialist

Apr 7, 2022 12:04 PM in response to XSemperIdem5

Hi XSemperIdem5,


Thank you for using the Apple Support Communities! The first step we would recommend is trying the First Aid feature of Disk Utility as listed here:


How to repair a Mac disk with Disk Utility


If the issue remains, we would also suggest the steps in the following Seagate Support page that may help:


USB External Troubleshooter


Hope this helps!

Have a great day.


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User profile for user: Grant Bennet-Alder
Grant Bennet-Alder
User level: Level 10
132,469 points

Apr 7, 2022 12:12 PM in response to XSemperIdem5

If you initialized the drive using Seagate Utilities (or failed to initialize the drive with Disk Utility when new) it is controlled by Seagate Utilities.


Unless/until you load Seagate Utilities on the new computer, the data on that drive are dead to you.


We always advice anyone who asks to initialize a new drive with Disk Utility to avoid such issues.

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External drive not mounting after upgrading from Lion to El Capitan

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