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Question: Any re boot advice?

My 2012 iMac, High Sierra 10.13.4, will not complete the boot sequence. It gets to the Apple logo, the bar under the logo runs to about three quarters of it's length, it cuts to the white screen. It stops on the white screen and freezes.

I am not sure if 'Safe Mode' is working. I tried rebooting by holding down the power button and pressing the shift key but it goes through the same sequence.


It did change to a grey screen which allowed a choice of the setup screen which allowed me to select the hard drive and I did get it to boot up to the desktop but it quickly returned to the white screen again when I tried clicking on Safari.


Does anyone know a way to do a check on the boot sequence or access the safe mode in another way? If I do get back to the desktop is there a check sequence which will find why it reverts to the white screen? Any helpful suggestions will be gratefully welcomed.

iMac, macOS High Sierra (10.13.4)

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Try to reset the NVRAM per the directions in How to reset NVRAM or PRAM on your Mac - Apple Support and let us know if that fixes the problem. If it does not there is more that can be done to troubleshoot it.

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Apr 23, 2018 6:15 AM in response to Clayboss In response to Clayboss

Try to reset the NVRAM per the directions in How to reset NVRAM or PRAM on your Mac - Apple Support and let us know if that fixes the problem. If it does not there is more that can be done to troubleshoot it.

Apr 23, 2018 6:15 AM

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Apr 23, 2018 6:15 AM in response to Clayboss In response to Clayboss

Try an SMC reset:

How to reset the System Management Controller (SMC) on your Mac - Apple Support

Try booting into Recovery Mode and run Disk Utility > First Aid on your hard disk.

About macOS Recovery - Apple Support

Apr 23, 2018 6:15 AM

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Apr 23, 2018 6:11 AM in response to rkaufmann87 In response to rkaufmann87

Thank you for that very swift response. I am impressed already! I will have to see if this solution works for me later in the week as I am away from the iMac at the moment. I will let you know how it goes. Thank you again.

Apr 23, 2018 6:11 AM

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Apr 27, 2018 12:20 AM in response to macjack In response to macjack

Thanks macjack. I did try your suggestion but it repeatedly produced the previous result. If I can get it into recovery mode I hope it will be able to restore it from my backup drive with Time machine. I did use Internet revovery, and it resulted in the fault code 21 06F, do you have any ideas about this?

Apr 27, 2018 12:20 AM

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Apr 27, 2018 12:23 AM in response to rkaufmann87 In response to rkaufmann87

Thanks rkaufmann87, as I have posted to macjack, I couldn't get the mac to respond to the key commands but it did respond to the internet recovey keys in your link. It produced the fault code 21 06F. Do you have any suggestions?

Apr 27, 2018 12:23 AM

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Apr 27, 2018 6:11 AM in response to Clayboss In response to Clayboss

Clayboss wrote:


Thanks rkaufmann87, as I have posted to macjack, I couldn't get the mac to respond to the key commands but it did respond to the internet recovey keys in your link. It produced the fault code 21 06F. Do you have any suggestions?

Apple does not publish error codes, I looked for it however I wasn't able to locate any information on fault code 21 06f. My suggestion at this point is to make an appointment at your local Apple Store for a free diagnostic or take it to an independent Apple Authorized Service Provider to be professionally diagnosed and serviced.


Good luck.

Apr 27, 2018 6:11 AM

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Apr 27, 2018 6:37 AM in response to Clayboss In response to Clayboss

Until you have it diagnosed with someone with the correct tools (only an Apple Store or Apple Authorized Service Provider) then you are simply guessing. Get information, then decide what to do. Don't assume anything at this point.

Apr 27, 2018 6:37 AM

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Apr 27, 2018 7:01 AM in response to rkaufmann87 In response to rkaufmann87

I retried this and at last the alt+cmd+R+P key combination worked. I was able to run Diskaid and check the hard-drive. Everything seems to be running well now. I am going to copy all the files I want to keep before I shut down but I am hoping it will all go well for now. Thank you for your suggestions and the link.

Apr 27, 2018 7:01 AM

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Question: Any re boot advice?