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User profile for user: mister coffee
mister coffee Author
User level: Level 1
5 points

Mojave installation unbootable on external drive

I have a Mac Mini (late 2014) with its stock internal drive and an external SSD via USB. The external drive has Sierra and this is what I always boot from. The internal is a clone of the external just for backup, cloned via SuperDuper.


According to https://support.apple.com/en-us/HT210190 I can update directly to Mojave on this Mac Mini. I downloaded the installer from the App Store and ran it to install on the external drive. It took about 25 minutes and gave a "success" message, prompting me to restart to finish. When I restarted, it booted from the internal drive instead. I went to the Startup Disk pref pane and made sure the external was selected and tried again. It booted again from the internal drive. Good thing I had it as a backup :)


In the Startup Disk pref pane, the external drive is selectable but it still shows as a Sierra boot. I can tell the install did write to the external drive but I suppose it didn't finish. I ran the installer again -- it only took a few minutes and again showed "success" and a restart prompt. Same result.


Before I take the time to wipe the external drive and try a clean install (then restore all my stuff), anyone know what's going on?


thanks!

Mac mini, macOS 10.12

Posted on Nov 2, 2019 3:47 PM

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User profile for user: mister coffee
mister coffee Author
User level: Level 1
5 points

Posted on Nov 3, 2019 1:22 PM

Option at boot worked when I switched the keyboard to a different USB port. I can now boot into my external drive(s) but only via the boot menu, not by setting it Startup Disk pref pane. Not perfect but good enough...

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User profile for user: mister coffee
mister coffee Author
User level: Level 1
5 points

Nov 2, 2019 7:38 PM in response to mister coffee

More info:


I cloned the working internal boot drive back to the previously-working external SSD. So in theory I would be back where I started, with the SSD running Sierra and being my boot drive. But it still won't boot into it and it still shows as a valid choice in the Startup Disk pref pane. I tried resetting the NVRAM but no luck. Now I'm really confused :/

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User profile for user: mister coffee
mister coffee Author
User level: Level 1
5 points

Nov 3, 2019 1:05 PM in response to mister coffee

UPDATE:


I created a brand-new Sierra install on another USB external drive (HDD not SSD). I can't boot from this one either -- so it looks like I've lost the ability to boot from *any* USB drive. It's the same symptoms -- drive is selectable in Startup Disk pref pane but it boots to the internal drive anyway. Holding down option at startup does literally nothing -- no boot menu, it just goes right to booting from the internal drive as if no key is pressed.


For clarity, my keyboard is Apple wired.


I tried resetting the SMC -- the reset happened but no change in the issue.

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Mojave installation unbootable on external drive

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