macOS 15.4 update failed on external disk

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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

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Falko Zurell Author

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63 points

Apr 14, 2025 8:14 AM in response to Falko Zurell

I was finally able to update my external disk to 15.4. The internal disk is FileVault enabled. The external disk did not have FileVault enabled.

I've booted into the external disk with macOS 15.3.2 running. On the command line I've invoked the software update with the following command:

sudo softwareupdate -a --fetch-full-installer --full-installer-version 15.4 --launch-installer -R

Let this thing run through and it updated the external disk just fine this time. I think specifying the version of the installer and using the full installer might have made the difference.

Also found this explanation of the Apple Secure boot approach on Apple Silicon Macs which might give a hint at the root of the issues: https://eclecticlight.co/2023/03/15/ownership-of-apple-silicon-macs-matters-how-it-can-stop-external-bootable-disks/

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Answer 2

May 5, 2025 4:52 PM in response to Falko Zurell

I had the same problem on my M1 MBP -- after a number of failed attempts, it finally worked for me after I moved the external drive so that it was not connected to the "DFU port" -- this is just one of your USB-C / thunderbolt ports, and not plugging external bootable drives into this port is documented by Apple as a requirement, but it seems that after the initial install, the boot itself might work from any port, but upgrade does not? At least, that is my working theory.

I did not disabled File Vault on the internal drive (it was never on for the external). I did also allow the password for a user with rights to decrypt the internal drive to be stored in my keychain; I'm unsure if this was a factor.

How to identify the DFU port on Mac - Apple Support (NZ)

Install macOS on an external storage device and use it as a startup disk - Apple Support (NZ)

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Answer 3

Apr 5, 2025 9:33 AM in response to Falko Zurell

Update after my visit to the Apple Store for a service, they were successfully able to perform a DFU restore via Apple Configurator. Took about 15-20 minutes to complete, and the OS is now installed correctly with 15.4.

When I get home I'll try re-creating my separate volume for work and will begin the setup process for that, and report if it is successful. The technician seemed to think it may be something related to FileVault causing the issue, which may have affected the preboot partition although I'm surprised fully wiping the disk didn't fix that. So if you have access to another Mac running 14/15 with USB-C, you may have success doing a DFU restore. Note this will require the device itself to be wiped. As my device as already wiped the tech did not try a revive which also may have been successful.

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Answer 4

May 13, 2025 4:34 AM in response to BDAqua

I tried changing Thunderbolt cable to an Apple one, that didn't work (pleased really as a certified Thunderbolt cable should be the same as an Apple Cable). I didn't know about DFU port (which coincidently I was plugged into). I changed the port my external drive was connected to - success, I now have the latest MacOS installed! At last!

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Answer 5

Falko Zurell Author

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63 points

May 5, 2025 11:01 PM in response to bignose77

Now that worked for me too. Connected the external SSD to the non-DFU USB-C port and did the upgrade. All disks have FileVault enabled. This time the update went through without a problem. I thought I had tried this before (the non DFU port) without luck. Maybe I didn't pay enough attention which port I had used.

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Answer 6

tga3

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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 7

Udibr1

Level 1

14 points

Apr 6, 2025 7:18 AM in response to Falko Zurell

I just managed to update my external hard drive to 15.4 after first turning off fire vault. I think I already did that in the past and it failed so it could be that Apple partially fixed the installer

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Answer 8

Lookcool

Level 1

18 points

Apr 12, 2025 3:49 AM in response to crazyl999

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 9

Lookcool

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18 points

Apr 26, 2025 9:18 AM in response to pattybaby

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 10

May 9, 2025 10:16 AM in response to Falko Zurell

Hello Everyone,

I had the same problem. The installer doesn't work. I am running an Samsung 990 pro in a Thunderbolt ZikeDrive USB4 40Gbps NVMe M.2 SSD-Enclosure enclosure on a MacBook Pro 14" 2023. I could not install the update no matter what I tried. I ended up making a clone of my data via Carbon Copy Cloner and then did a clean install with a bootable disk from the latest version of MacOs Sequoia 15.4.1 available in the AppStore. That worked an then I transferred my data back wit migration assistant. It was work but now everything works like a charm. Hope this helps.

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Answer 11

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 12

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 13

BDAqua

Level 10

250,247 points

May 5, 2025 11:38 AM in response to CAPAMAC

Have you booted into restore mode & used Disk Utility to repair the drive?

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Answer 14

May 9, 2025 11:25 AM in response to CAPAMAC

I had the same problem and could only get it to work after I backuped my data and did a clean install from a bootable volume with MacOs 15.4.1 from the app store. Now everything is running again.

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Answer 15

Apr 4, 2025 2:27 PM in response to Falko Zurell

I have the same issue and error report. This has happened consistently after trying to install the macOS 15.4 update on an external drive.

Device info:

M1Pro MacbookPro 14in
512 GB internal SSD
2 TB external SSD connected via Thunderbolt 3

I have tried:

Removing my laptop from FindMy
Turning off SIP on the internal drive
Downloading and running the full installer to install to the external drive
Using Recovery to install to the external drive
Using the bless command from the Recovery mode terminal. (See: screenshot)

So based on the screenshot and my attempt to enable SIP on the external drive after installation failed it looks like a local boot policy is never set due to a preboot error.

Anyone have any luck with a fix?

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