User profile for user: Falko Zurell
Falko Zurell Author
User level: Level 1
33 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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User profile for user: Falko Zurell
Falko Zurell Author
User level: Level 1
33 points

Posted on Apr 2, 2025 11:53 PM

Just tried it again and it fails. After startup I get the message that the machine was shut down unexpectedly. Saw the following error message in the details that are going to be send to Apple:


panic(cpu 8 caller 0xfffffe001bfbad28): /AppleInternal/Library/BuildRoots/17229e79-0523-11f0-a80c-fe9e33ca05fa/Library/Caches/com.apple.xbs/Sources/apfs/kext/apfs_filter.cpp:1713 Assertion failed: !(cpOffset % CRYPTO_SW_BLKSIZE)
Debugger message: panic



Looks like an issue with the Installer.


I do NOT have the decryption key for my internal SSD in my keychain in the macOS booted from the external disk. This is deliberate to not have access to the Internal SSD by default. Maybe that's of an issue for the installer that one of the disks (the internal SSD) is encrypted and requires a password. Although that disk should not be touched by this update.

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User profile for user: Richard Mac User
Richard Mac User
User level: Level 1
66 points

Apr 11, 2025 4:46 AM in response to Falko Zurell

Well glad to see there are a number of us with unusual setups.


Mine is Mac mini M2 Pro, bootable from external drive.


As with others, the internal drive updated to 15.4 no problem (as did my backup M2 Mini), but not the external drive. In 2 profiles, I have tried updating multiple times, in standard mode and safe mode. On the spare profile it goes through the procedure, but afterwards still on the old version, on my main profile I get the dialogue box saying my Mac has restarted after a problem.

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User profile for user: Lookcool
Lookcool
User level: Level 1
12 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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User profile for user: Falko Zurell
Falko Zurell Author
User level: Level 1
33 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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User profile for user: Falko Zurell
Falko Zurell Author
User level: Level 1
33 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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User profile for user: crazyl999
crazyl999
User level: Level 1
32 points

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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User profile for user: tga3
tga3
User level: 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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macOS 15.4 update failed on external disk

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