Mac external disks fail to upgrade to macos sequoia 15.4, while internal disks can be upgraded to 15.4.

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Mac external disks fail to upgrade to macos sequoia 15.4, while internal disks can be upgraded to 15.4.

I'm using a Mac mini, and I'm used to having an external disk as my system disk, and I recently found that I couldn't upgrade the external disk from macOS Sequoia 15.3.2 to macOS Sequoia 15.4. Download the system, and then restart when ready to install, when the first progress bar is stuck, and then boot into the desktop to say that my mac restarts because there is a problem, and then no matter what kind of way can not update to macOS 15.4, but the internal disk can be upgraded to 15.4 normally, If you have a good way to share here, I think many people have this problem. Finally, I successfully upgraded the external disk to macos Sequoia 15.4.

Posted on Apr 12, 2025 1:12 AM

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Answer 1

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Lookcool Author

Level 1

18 points

Apr 12, 2025 3:43 AM in response to Lookcool

My steps were as follows to successfully update the external disk to macOS 15.4:

1. Upgrade the internal disk to the latest macOS, which was 15.4 at that time.

2. Turn off the FileVault for both the internal and external disks.

3. Boot in the internal disk and download macOS Sequoia 15 from the App Store, then install it on the external disk.

(Note: Make sure to download and install 15.4 from the App Store on the internal disk. Doing it on the external disk will fail.) 

I believe that many people will encounter this problem: the external disk update fails. I hope my solution can be helpful to everyone.

If you update the external disk to macOS 15.4 according to my steps successfully, please reply to me here 😂😆. let more mac user know!

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Answer 2

Lookcool Author

Level 1

18 points

Apr 19, 2025 2:31 AM in response to Lookcool

The same update failure issue occurred when I upgraded from macOS 15.4 to 15.4.1.

The following is my solution:

Turn off FileVault on the external disk and the internal disk.

2. Close Find My Mac on Settings.

3. Normal update on Settings.

Then I successfully updated to macOS 15.4.1 from 15.4.

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Answer 3

tbirdvet

Level 6

17,096 points

Apr 12, 2025 6:08 AM in response to Lookcool

As an alternate method (works every time):

Format external to APFS

Boot into recovery

select install OS and pick external

Once that is done you can select MA to install all files from TM backup or other.

After that you can boot from the external and turn on FileVault if desired.

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Answer 4

Lookcool Author

Level 1

18 points

Apr 19, 2025 2:35 AM in response to Lookcool

For macOS updates, do we have to first turn off the FileVault on both the internal and external disks to successfully update? This is too troublesome. I hope Apple can fix this bug.

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