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Help! Cannot Reboot iMac

A message popped up on my iMac (running Catalina) indicating that updates that were installed during the night required that the computer be restarted. While going through the start-up sequence, the screen displayed a "small circle with a slash through it". After waiting about 40 minutes with the symbol still remaining, I shut down the computer using the power button. When I restarted, again, the computer went through the normal start-up sequence. After a couple of minutes, the same symbol was displayed.


I never experienced anything like this before. Could someone please help? Thank you so much.

iMac Line (2012 and Later)

Posted on Feb 20, 2021 7:00 AM

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Question marked as Top-ranking reply

Posted on Feb 20, 2021 8:18 AM

You also may want to look at this article: If your Mac starts up to a circle with a line through it - Apple Support

4 replies

Feb 20, 2021 7:12 AM in response to kitjv

Shutdown computer via Power Button if needed. Disconnect all eternal drives. Restart and immediately hold the - Shift - key. This is Safe Mode and does a repair Disk, clears cache files and Only Loads Apple Software - slow booting - Normal. Let it run this way for 10 - 15 minutes and reboot in normal mode.

Feb 20, 2021 8:39 AM in response to 6x6

6X6: I read & followed the instructions in the article which essentially restarts the computer in Recovery Mode. I then ran Disk Utility on all volumes. Looks like problem is solved! Curiously, I wonder why the problem occurred in the first place. Any thoughts?


P. Phillips: Thank you for the suggestion. It sounds like restarting in Safe Mode essentially is another road to launching Disk Utility which seemed to have resolved my problem. Thank you.

Help! Cannot Reboot iMac

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