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After every shutdown/restart i have to reinstall MacOs to avoid prohibitory error on start up.

Every time i shutdown or restart my computer I have to force into Mac OS Recovery and reinstall the MacOs Catalina or else i get the black screen with the prohibitory symbol upon reboot. Anyone know what could be causing this? I've already checked and made sure that my start up disk is set to my MacOs SSD. Please help :)

iMac Pro, macOS 10.15

Posted on Jul 9, 2021 2:42 PM

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Question marked as Top-ranking reply

Posted on Jul 9, 2021 2:47 PM

Hello, Ilyabab.


• FIrst - very important - make sure you have an up to date TIme Machine backup.

• Restart the iMac (⌘R) and run Disk Utility First Aid on your boot volume and startup drive.


If all is well there, see if the problem still happens in Safe mode (hold the shift key down at startup). It takes longer to safe boot so be patient.

How to use safe mode on your Mac - Apple Support 


Safe mode forces the OS to clear certain caches and logs and do other miscellaneous housekeeping. It's non-destructive to user data so is safe to do.  Very often certain weird software behavior is corrected by simply logging in this way as a troubleshooting method. When you're in safe boot, the machine will not be at its best performance, especially with graphics, but that's normal.


Does the problem persist while in Safe mode? 

Exit safe mode by restarting your Mac normally and re-evaluate the issue again after a normal reboot.

4 replies
Question marked as Top-ranking reply

Jul 9, 2021 2:47 PM in response to Ilyabab

Hello, Ilyabab.


• FIrst - very important - make sure you have an up to date TIme Machine backup.

• Restart the iMac (⌘R) and run Disk Utility First Aid on your boot volume and startup drive.


If all is well there, see if the problem still happens in Safe mode (hold the shift key down at startup). It takes longer to safe boot so be patient.

How to use safe mode on your Mac - Apple Support 


Safe mode forces the OS to clear certain caches and logs and do other miscellaneous housekeeping. It's non-destructive to user data so is safe to do.  Very often certain weird software behavior is corrected by simply logging in this way as a troubleshooting method. When you're in safe boot, the machine will not be at its best performance, especially with graphics, but that's normal.


Does the problem persist while in Safe mode? 

Exit safe mode by restarting your Mac normally and re-evaluate the issue again after a normal reboot.

Jul 9, 2021 3:37 PM in response to Ilyabab

You’re welcome.


Google Drive is a service that is similar in function to iCloud Drive, giving the user the ability to save files and documents into cloud storage and allow others to access those files there.

As with iCloud Drive, it is not a system backup solution.

Time Machine is the backup system you should be looking at to protect yourself against unforeseen computer failure.

After every shutdown/restart i have to reinstall MacOs to avoid prohibitory error on start up.

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