Bootloop install high sierra or boot OSX

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Level 1

9 points

Bootloop install high sierra or boot OSX

Hi everyone I have this imac that until yesterday has never given me problems, today it does not start going in bootloop even if I try holding the capital key it does not start, I tried to see if the hard disk is good both with crystal disk info both with knoppix but there are no problems, even if I only try to boot on a usb stick with high sierra above it goes into bootloop, what can I do to check the problem or give more information to you thanks to who will help me?

iMac Line (2012 and Later)

Posted on Jun 12, 2020 1:16 PM

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Answer 1

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HWTech

Level 9

55,934 points

Jun 12, 2020 2:03 PM in response to acidburn87

How far does the iMac get in the boot process before it restarts?

Can you boot into Safe Mode?

Recovery Mode (Command + R)? Or Internet Recovery Mode (Command + Option + R) to bypass the local recovery mode partition?

Try a PRAM reset (hold the PRAM reset for at least three chimes or a full minute so it activates several times). Sometimes Apple hardware gets stuck booting macOS incorrectly if the NVRAM contains another boot option which is set. Just happened to me from a failed macOS install.

Post a copy of the drive's SMART report from using Knoppix using the "Additional Text" icon which looks like a piece of paper.

It also never hurts to run the Apple Diagnostics.

Edit: Also what is the exact model of this computer? You can get this information by entering your serial number here:

https://checkcoverage.apple.com/

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Answer 2

acidburn87 Author

Level 1

9 points

Jun 13, 2020 6:32 AM in response to HWTech

Hi I checked everything calmly before writing again, in safemode I managed to enter only 1/2 times but now it no longer works, at the loading screen the progress bar arrives halfway and the mac restarts.

Even in recovery mode there is nothing to do.

This imac is a late 2019, if I try to hold down the D button for the test it does not start, in my opinion there is a need for a usb boot, and now even knoppix doesn't start but hangs on the attached image.

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Answer 3

HWTech

Level 9

55,934 points

Jun 13, 2020 1:11 PM in response to acidburn87

You mentioned using Knoppix in your original post so did it boot to the Knoppix desktop at one point? Usually when Knoppix doesn't boot to the Desktop it is due to a GPU issue. I've only encountered this problem with Macs which had faulty GPUs. I haven't used Knoppix v8.6 on a 2009 Mac though so this could be a Knoppix issue with the newest version unless of course it booted fine for you previously. Unfortunately due to the way Macs boot the first Knoppix boot menu is unavailable to customize the boot parameters as suggested in the pictures you took.

We can, however, check the health of the hard drive from the Knoppix command line shown in your pictures. If you don't have the "#" prompt available, then try pressing the "Return" key to see if it appears. If pressing the "Return" key doesn't make a command prompt with "#" appear, then try pressing Control + C together. Try pressing Control + C a couple of times in case it doesn't register right away because the system is too busy.

Or you can switch to another terminal (TTY) by pressing Control + Alt + F3 to reach a command prompt.

If you have a command prompt, then just type the following command and press the "Return" key at the end of the line to execute the command:

smartctl  -a  /dev/sda  |  less

This will display the internal drive's health report. You can use the up & down arrow keys or a mouse wheel to scroll up & down the report. Take a couple of pictures of the report to post here.

Both a drive/OS failure or a GPU failure are consistent with the problems you are having booting macOS. I'm guessing the GPU is the culprit unfortunately there is no way to know for sure if the GPU is bad.

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