Problems installing MACOS on USB drive

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Problems installing MACOS on USB drive

Macbook Pro M4 trying to install mac OS (26.2) onto an external usb drive. Booting into Recovery mode, select Reinstall Mac OS. Then i select the volume in the external drive i want to install the OS on and the install starts. After several hours the macbook pro reboots from the internal drive. Restarted holding the Option key but it just boots into the internal drive. I go into System Settings/Startup Disk and click on the external volume that shows it has OS 26.2 on it. When I click restart I get an error:

The version of the MacOS on the selected disk needs to be reinstalled. This volume cannot be used since it has a secure token without any users.

I then booted into Recovery mode and launched Startup Security Utility and changed the allow external devices to ALWAYS ALLOW the changed the Security setting to the one with LESS Security. I then went into Disk Utility and erased the volume that had the problem. I am now trying the OS Reinstall on that same volume but it will take a couple if hours until I know if this works. If you have any tips, I’d appreciate it!

MacBook Pro 14″, macOS 26.2

Posted on Feb 3, 2026 6:05 PM

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Answer 1

Feb 5, 2026 1:21 PM in response to George Spiese

Here is an Apple article with instructions for installing macOS onto an external drive, it has a very important detail for M-series Macs.....you cannot use the DFU USB-C port during the install process:

How to use an external storage device as a Mac startup disk - Apple Support

With an M-series Mac, the volume must be a GUID partition and APFS file system (top option).

FYI, an M-series Mac no longer has the various startup keys.....it has just one special option which is holding the power button for about 7-8 seconds. When holding the power button, you will see "Hold power button for startup options" (or something like that)....release once it changes to "Loading". This is the equivalent of Option Booting on Intel Macs and gives you access to various boot volumes, allows you to select Safe Mode, or boot to Recovery Mode (aka "Options").

Mac startup key combinations - Apple Support

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Answer 2

Feb 4, 2026 8:06 AM in response to George Spiese

From your original posting:

The second procedure, installing AFTER adjusting security permissions and authorizing the External drive, is the correct one, and should produce an external drive that should boot that Mac.

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Answer 3

TheLittles

Level 10

205,175 points

Feb 3, 2026 7:03 PM in response to George Spiese

"Problems installing MACOS on USB drive: [...]I am now trying the OS Reinstall on that same volume but it will take a couple if hours until I know if this works. If you have any tips, I’d appreciate it!"

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Backing Up First:

Take this as a learning experience, knowing to always create a Time Machine Backup prior to making any major changes(i.e. installations, uninstalltions, and reinstalations, and backups), whatsoever. That way, you can have something to restore your Mac from, should anything go wrong during or after the change.

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Answer 4

Feb 4, 2026 7:55 AM in response to TheLittles

The usb drive has nothing on it yet. I do regular backups and do them before any changes. BTW the restore of macos to the usb drive failed again. Research tells me the usb drive needs to be formatted MacOS Extended. I was trying to install the os onto a APFP formatted volume. I’ll try a different (smaller) usb drive to install the os onto. I don’t want to format my 8TB usb drive in MacOS Extended because i want to use one 2TB volume for my Carbon Copy Cloner (CCC) backups. CCC prefers APDP formatted volumes and I can’t reformat just one volume, I have to format the entire drive in one format. So I’ll keep my 8TB drive formatted in APFP.

I also used Terminal to download the Tahoe 26.2 version and am in the process of using Terminal to create a bootable OS on a usb drive.

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Problems installing MACOS on USB drive

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