Unexpected restart behaviour

Question

Unexpected restart behaviour

Environment: External SSD with Mojave and the native drive with Big Sur Version (11.0.1)

: iMac (Retina 5K, 27-inch, 2017) 16gb RAM

Back story: Running Mojave and need to access Big Sur.

This is not Beta software!

Problem:

1- As I cannot see/select Big Sur from Prefs/Startup disk in Mojave, I shut down the computer.

2- I "option key" boot into Big Sur.

3- I scheduled a startup using Prefs/ Energy Saver / Schedule

4- The computer started the next day at the correct time BUT booted using the Mojave disk NOT the Big Sur disk.

I disconnected the remote drives and it did reboot that started in Big Sur as expected. When I connected the Mojave drive and did a restart from Big Sur it booted into Mojave, not Big Sur.

Does anyone have a solution?

iMac 27″ 5K, macOS 10.14

Posted on Dec 13, 2020 2:59 PM

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Answer 1

Top-ranking reply

PRP_53

Level 10

91,777 points

Jan 15, 2021 4:48 AM in response to ManUFanatic10

Go System Preferences >> Startup Disk with the external Dive Attached. Lower Left of panel UnLock the padlock with computer password. Change the Startup from External to Internal drive. ReLock padlock and attempt a restart

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Answer 2

Jan 15, 2021 7:19 AM in response to PRP_53

P. Phillips - Worked a charm. Thank you! After following your instructions, I did a restart and it started into B.S. I then powered off, waited a bit, and pushed the power button. It started into B.S.

However I wish I had clicked Helpful instead of Solved.

After I boot into the external drive, I am unable to specify the internal drive in the startup disk window as it does not show up.

I started the unit and, using the Option Key, booted into Big Sur.

Then when I restart normally, i.e. not using Startup Disk, it boots back to the external drive not the internal. Weird but thanks for the work around.

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Answer 3

PRP_53

Level 10

91,777 points

Jan 15, 2021 7:32 AM in response to ManUFanatic10

Have worked on another thread where person could not boot to external SSD of Catalina from a Big Sur installation to internal drive even when using the Startup Disk change in System Preferences. It was eventually fixed ( as per person ) but involved Re_Partitioning the external drive and doing a Clean Install of Catalina to external SSD. This is all sounding like to additional Apple Snapshot Volume added in Big Sur is really locking down this Internal Drive Boot and trying / attempting to boot to External Drive to another macOS.

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Answer 4

Jan 15, 2021 1:58 PM in response to PRP_53

Additionally, when I select BootCamp (on the internal drive) as the startup drive, Widows 10 starts no problem. After I shut down Windows and the computer is off and I then restart the computer it boots into Windows rather than Big Sur.

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Answer 5

Jan 15, 2021 4:35 AM in response to ManUFanatic10

Clarification:

When I am running BS 11.1:

There is a clean Mojave disk attached.

On a restart, power on, or scheduled start the unit starts into Mojave not B.S.

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Answer 6

PRP_53

Level 10

91,777 points

Jan 15, 2021 2:15 PM in response to ManUFanatic10

One must use the Option key held immediately at startup this will load Boot Manager and then choose the desired OS. That being macOS Big Sur OR windows 10

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Answer 7

Jan 15, 2021 7:17 PM in response to PRP_53

Back to the original Issue. When I restart Big Sur from Big Sur it should restart into Big Sur.

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Unexpected restart behaviour

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