iMac stuck in Kernel Panic Loop after upgrading to High Sierra

riddl wrote:

No, there are no Antivirus and/or Cleaning Apps installed. If you write "maintenance" -> there are a couple of cli tools installed via brew.

Okay that's good. Try restarting in the Recovery Partition (Command + R) and if it boots go to Disk Utility and run First Aide 2-3 times. If no errors occur, then exit DU and try re-installing Mac OS from the Recovery Partition and then attempt to restart.

What I am suspecting is your HD may have failed during the installation. That can occur which is no fault of Mac OS, it simply means the HD was failing already and the added work of installing the OS pushed it over the edge. The KP may be due to the failed HD. In that case book a visit to your local Apple Store or AASP to have it professionally diagnosed and serviced.

BTW, if the computer is still covered by AppleCare (I doubt it is) then just take it in to be serviced.

My father tried upgrading his 2014 iMac to High Sierra last night, and his now facing the kernel panic loop issue. I can’t boot into recovery mode, as it seems, the iMac isn’t connecting to his Apple wireless keyboard. Any suggestions?

Hi MadBeaverDK, if you don't happen to have access to a wired Apple keyboard, then borrow a regular, wired, USB keyboard from a Windows machine. You want one with the Windows key on it (4 panes of glass at an angle, between the Ctrl and Alt keys). The Windows key, for this purpose at least, is equivalent to the Command key on the Apple keyboard. Take the batteries out of the Apple wireless keyboard so that you know it is offline, then plug in the Windows keyboard. Hold down Windows+R and then power the iMac on. You can release the keys when you see the Apple logo.

I tested this procedure on my 2011 iMac using a Logitech K120 USB keyboard and it worked just fine. Good luck to you.

Hey CrankyProgrammer

Thank you for your reply. Wish I had known that 3 weeks ago. My dad got impatient, so we handed in his iMac for service. They fixed it somehow. But it’s nice to know, that a wired windows keyboard can do the trick.

What happens when you reset the PRAM per the instructions in iMac SMC and PRAM reset ?

I have the same problem with a Mac Pro (last version before the redesign). I’m currently reinstalling from a time machine backup.

I would have suggested another approach however because you are proceeding before we have an opportunity to reply we'll just have to see how big a mess you have.

Okay, a couple of questions. Do you have ANY antivirus, cleaning or any other third party "maintenance" apps installed on the computer? If so which?

Cool, looks like your original install was corrupted by something. Glad you are back up and running.