iMac stuck in boot loop after using it to create BigSur USB

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iMac stuck in boot loop after using it to create BigSur USB

I am looking for some help after I seem to have caused my iMac to get stuck in a boot loop. To explain how I got here:

I recently erased my MacBook Air 2020 but after having trouble reinstalling the osx by recovery mode I decided to use my iMac to create a bootable BigSur USB drive that I could then use to reinstall the OSX onto my MacBook Air. So after creating the USB using terminal, for some reason the USB drive wouldn't dismount without force ejecting it. So I simply shut down the iMac in order to remove the USB drive safely. However, after booting up my iMac again it is now stuck in a boot loop and keeps displaying the 'your computer restarted because or a problem...' message.

I have since tried the following things to solve the issue:

removed all USB connections

Reset NVPRAM

Tried to boot up into recovery mode to use disk utility to check the drive but recovery mode doesn't give me the option to open disk utility

I really hope I haven't lost everything on my iMac as it's my main work computer.

Any help will be greatly appreciated thanks!

Simon

iMac 27″

Posted on Jun 19, 2024 7:39 AM

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Answer 1

Top-ranking reply

HWTech

Community+ 2026

Level 9

70,982 points

Jun 21, 2024 9:17 AM in response to Simon Finley

You've done some great troubleshooting already. Safe Mode is definitely the next thing to try.

If Safe Mode doesn't allow you to boot, then you could try Verbose Mode (Command + V) or even Single User Mode (Command + S, if available). If Single User Mode is available, then it may allow you to copy your data to external media assuming you know how to use the command line.

I would suggest running the Apple Diagnostics to see if any hardware issues are detected. The diagnostics rarely detect issues, but it never hurts to check.

What is the exact model of the iMac and version of macOS currently installed on it? You can get the exact model by entering the system serial number on the check coverage page here:

Check Your Service and Support Coverage - Apple Support

Have you tried to boot the Big Sur USB installer on that iMac? I'm assuming the iMac is compatible with Big Sur since you used it to create the USB installer.

When you reset the PRAM, did you hold the PRAM Reset for at least two chimes? I find the reset doesn't always work until the second chime.

Maybe even try an SMC Reset (Intel Macs only)....for an iMac that involves unplugging the AC cord for a minute. I like to also press the power button to help drain the circuits.

When you boot to Recovery Mode or the installer, how far does it get? Make sure to try Internet Recovery Mode using Command + Option + R (assuming an Intel Mac).

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Answer 2

BDAqua

Level 10

250,409 points

Jun 19, 2024 1:45 PM in response to Simon Finley

So, no backup at all?

Tried to boot up into recovery mode to use disk utility to check the drive but recovery mode doesn't give me the option to open disk utility.

Do you see a Utilities menu in the top toolbar wilst in Restore Mode?

Safe Boot, (holding Shift key down at startup), does the problem occur in Safe Mode? Could take 10 minutes or more.

Safe mode attempts to repair Disks & clears lots of caches & loads safe Drivers, & prevents loading of 3rd party extensions, so if Safe Mode works try again in regular boot.

Or... Start up from macOS Recovery

Command (⌘)-R

Install the latest macOS that was installed on your Mac.

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iMac stuck in boot loop after using it to create BigSur USB

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