macOS 15.4 update failed on external disk

Question

Level 1

63 points

macOS 15.4 update failed on external disk

I've got a maybe somewhat odd setup here. MacBook Pro M2 Max with macOS Sequoia 15.4 running on the internal SSD (APFS, encrypted). In addition I have an external NVMe SSD (Samsung T7) where I've also installed macOS Sequoia to be used as StartUp-Disk if need be. With that setup I keep my private and my corporate macOS installations physically separated. "Just" using the same MacBook Pro to run them.

Now I tried to apply the latest update from macOS 15.3 to 15.4 on my external SSD. The update shows, the external disk is set as StartUp Disk and the update process starts. It looks like it does the update with multiple reboots and all. But after it's finished and log in to the macOS it still shows the update 15.4 as available. There were no apparent errors during the update process. But I noticed that wen I log in after the update the system complains that it was improperly shut down and whether it should report that.

Any idea how to debug this? The update worked just fine on the internal SSD without any issue.

MacBook Pro 14″, macOS 15.4

Posted on Apr 1, 2025 5:54 AM

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Answer 1

Lookcool

Level 1

18 points

Apr 12, 2025 3:33 AM in response to Falko Zurell

I'm not sure what factors led to the successful update. 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.)

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Answer 2

Falko Zurell Author

Level 1

63 points

Apr 12, 2025 1:11 PM in response to Falko Zurell

Just tried again:

1.) turned off FileVault on the internal SSD at 15.4 (funny enough that was instant, no hour long decryption)

2.) turned off FileVault on the external SSD at 15.3.2 ( took about one hour to decrypt)

3.) booted from Sequoia 15.4 USB stick and installed on the external SSD.

still same issue. After finish and reboot the external SSD still reports its at 15.3.2

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Answer 3

Apr 17, 2025 1:57 AM in response to Falko Zurell

Last update from me, the release of 15.4.1 has resolved my issue for my dual internal volumes. Both are now up to date on 15.4.1, one upgrading from Sonoma 14.7.5 without any error messages. Both volumes also had FileVault enabled during the upgrade process. I hope that everyone else also has success with their external volumes - I am unable to test this currently.

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Answer 4

tga3

Level 1

0 points

Apr 17, 2025 10:09 AM in response to Falko Zurell

I had the same problem upgrading a second boot partition on the internal SSD to 15.4 (multiple failures) after upgrading the primary boot partition to 15.4. The solution was to use 15.4.1.

I upgraded the primary successfully to 15.4.1, then booted into the secondary and upgraded it to 15.4.1. Worked fine the first time.

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Answer 5

Falko Zurell Author

Level 1

63 points

Apr 19, 2025 3:26 AM in response to Falko Zurell

Still an issue with the 15.4.1 update. Internal SSD is on 15.4.1 already (filevault enabled). External SSD is on 15.4 (FileVault enabled). Update runs through, but then after login shows an unexpected restart and still version 15.4. Also the trick with the full install via command line didn't work:

~ sudo softwareupdate --fetch-full-installer --full-installer-version 15.4.1 --launch-installer -R
Password:
Scanning for 15.4.1 installer
Install failed with error: Update not found

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Answer 6

Apr 24, 2025 9:53 AM in response to Falko Zurell

I have the same problem. I am running a rented M2 Macbook Pro with an external Samsung Nvme 2TB Disk via Thunderbolt 3.1 and I am unable to install the newest update of MacOs Sequoia 15.4.1.

I am beginning to regret having installed Sequoia at all, the previous Sonoma and Ventura worked well and now there is only chaos. I have had some Time Machine issues as well, and GarageBand Sound Library is not loading and GarageBand itself is also warped. It's very demoralising. I hope Apple figures this out soon. It's unnerving to have such an unstable system!

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Answer 7

CAPAMAC

Level 1

27 points

May 4, 2025 11:56 AM in response to pattybaby

Same Issue Also having Issues with M2 MacBook Pro,

I still can't install 15.4.1 ?? Runs but then restarts without change.

Also I had made an emergency disk with Sequoia 15.3.1 It will not update to 15.4.1?

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Answer 8

CSGO

Level 1

13 points

May 6, 2025 9:07 PM in response to Falko Zurell

The same issue, the built-in version is 15.4.1, the external version 15.3.2 cannot be upgraded to 15.4.1. The upgrade process requires entering a password, and it seems to be completed, but after entering the desktop, it is still 15.3.2, with no error prompts.

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Answer 9

NowApple

Level 1

13 points

May 9, 2025 5:41 AM in response to ameenjuz

We have installation issue 15.4 on external drive to MacBook Air M1

which one Mac model you are using

Does it mean I should be able to install Sonoma on external drive instead?

If so, how can I download the Sonoma version?

Many Thanks

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Answer 10

May 9, 2025 11:22 AM in response to Falko Zurell

I wonder why my previous reply was erased? I had the same problem trying to update MacOs 15.4.1, the installer didn't work on my external SSD startup drive. I did a back up of my external disk and then wiped it. Did a clean install from a hard disk on which I had installed the latest bootable version of MacOs Sequoia 15.4.1 from the Apple App Store and then ran migration assistant to restore my data. Now everything is running smoothly. I hope I don't have to repeat this every time I do an update, but in the end I was at least able to rid my hard disk of some old junk I had been dragging around for ages. I don't think an external Mac startup volume works well under a USB-C setting, I think it has to be a thunderbolt connection with an apple cable. Hope this helps.

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Answer 11

CAPAMAC

Level 1

27 points

May 5, 2025 10:34 AM in response to 0xfeedface

Still not working for me... 3 tries to install 15.4.1 shows as start-up but am getting this message when trying to start up ..

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Answer 12

tbirdvet

Level 6

16,439 points

Apr 2, 2025 5:00 AM in response to Falko Zurell

I have 15.4 on my internal drive APFS. I made two external TB drives as boot drives (clone of my internal) and no issue using neither one. All my external drives are APFS with FileVault on.

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Answer 13

Apr 2, 2025 7:37 PM in response to Falko Zurell

my problem is after upgrade to 15.4, my M4 Mac mini can't boot from external SSD , it just shows a blank screen and keep reboot for a while. I have reinstalled the OS, and still get a blank screen.

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Answer 14

ameenjuz

Level 1

8 points

Apr 2, 2025 10:07 PM in response to aransh

I have a same issue macOS Sequoia 15.4 during installation on External drive but in internal drive no issue

i think that it has installer bug

we hope Apple fix this issue

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Answer 15

tbirdvet

Level 6

16,439 points

Apr 3, 2025 4:41 AM in response to ameenjuz

No issue here. I've done two different external drives and all installs no issue and both boot fine using 15.4. My external drives stared with 15.3.2 before updating.

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