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Unable to boot from external SSD after security update

Hello everyone, I was tracking a topic regarding boot issues from an external SSD (Samsung t5 in my case).

I seems that after the latest security update (10.15.7) my iMac (late 2013) just won't boot from the external SSD and just endlessly keeps booting in recovery mode.

I have reset both the SMC and PRAM but to no avail. I tried the SSD on my MBP 2012 and booted just fine, so I guess it is not an SSD issue.

I also enabled the firmware security option while in recovery mode. This resulted in a folder/question mark bleeping icon. Then I in my turn would shut down my iMac from the power button, the 2nd, 3rd or 4th time the computer would boot.

I am lost as I am unable to fine a sustainable solution to make my computer working again. Any help or direction is more than welcomed.

P.S I even contacted Apple support but guess what, nothing happened as theirs approach to the matter was epidemic to say the least.

Posted on Mar 15, 2022 12:07 PM

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ThanasisPap Author

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4 points

Posted on Mar 16, 2022 12:46 PM

UPDATE

I disconnected everything, including the SSD, and performed an NVRAM reset.

The NVRAM reset was performed with a twist. I pressed the key combination but released them only after I repeatedly

heard the chime sound 3-4 times.

The reason for doing that was me reading in some post that performing several NVRAM resets might do the trick (although I know that what I did does not necessarily count as multiple resets) and out of pure frustration.

The system booted from the SSD and seems stable.

I will post after a few days pass, so as to close this.

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ThanasisPap Author

Level 1

4 points

Mar 16, 2022 12:46 PM in response to ThanasisPap

UPDATE

I disconnected everything, including the SSD, and performed an NVRAM reset.

The NVRAM reset was performed with a twist. I pressed the key combination but released them only after I repeatedly

heard the chime sound 3-4 times.

The system booted from the SSD and seems stable.

I will post after a few days pass, so as to close this.

a brody

Level 10

85,308 points

Mar 15, 2022 3:31 PM in response to ThanasisPap

Make sure Filevault is not enabled on the drive.

Use the Option key to boot the drive.

Owl-53

Level 10

102,577 points

Mar 16, 2022 4:01 AM in response to ThanasisPap

Sorry it did not work out .

Have seen some other users with similar issue especially with the Samsung T5 or sometimes even the T7.

Not sure was would be next step except to Reformat the entire drive and Reinstall the OS Directly to the drive

In so doing it would put down a new Partition Map.

Owl-53

Level 10

102,577 points

Mar 16, 2022 3:14 AM in response to ThanasisPap

Make sure Only the External Bootable Drive and no over external drives are attached to the computer and directly attached.

ThanasisPap Author

Level 1

4 points

Mar 16, 2022 3:57 AM in response to Owl-53

Thank you, that was my approach but it made no difference. There were no other hard drives in the first place and on top of that I had all peripherals disconnected as well.

ThanasisPap Author

Level 1

4 points

Mar 16, 2022 12:37 PM in response to a brody

Filevault was not enabled and the SHIFT key was not working (meaning it was producing the anticipated results).

Thank you for taking the time to reply.

ThanasisPap Author

Level 1

4 points

Mar 19, 2022 11:52 AM in response to ThanasisPap

Everything seems to be working fine now.

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Unable to boot from external SSD after security update