Help please!

[PatiPhillips]

I installed the latest big sur beta last night. Now my imac will not boot up. It started with shutting down about every 20 seconds and then rebooting itself. I booted up into recovery and tried to reinstall the operating system, only choice was big sur. Same problem with it rebooting every 20 seconds. Rebooted again into recovery and this time chose reinstall from time machine. Chose a date from before this last beta update. Now I hear the start up sound, then the apple logo then the slider bar goes half way and a black screen appears. I cannot do anything. I tried to boot up into recovery, nothing, tried completely turning off the computer and unplugging it, still nothing. I have searched the internet to no avail. Dummy me, it is my main computer.

 

[Mr Todhunter]

Maybe I’m silly but try PRAM and SMC reset. You never know. Or , if it still starts and hangs halfway try booting from en external Hd.

 

[thekev]

Betas are inherently unstable. This kind of thing can happen, which is why you shouldn't use them unless there's a reason you really need to. If you need to update software for an upcoming iOS or MacOS, that's a good reason, but you should still try to maintain something with Catalina and be extra diligent about backups.

It's probably freaking out once it starts loading various drivers. You should try to clean install Catalina in this case, not roll back. I doubt you have failing hardware.

 

[PatiPhillips]

Thanks, I tried the PRAM reset, just get a circle with diagonal line through it. I am going to try to make a bootable disk from my apple laptop air running Catalina. I have to get an adapter first since all my items are regular usb and they will not work with my laptop. If and when I get this thing working again, I will not be using beta software again. Will wait for finished product and then extra time for all the bugs to be worked out. My backup disk, MyBook for Mac died a few weeks ago and I have not been able to replace it yet.

 

[peter34]

please check this thread, there are some solutions for Big Sur DB5 crashing

 

[minifridge1138]

Since you have an extra laptop running Catalina, you should be able to boot your iMac into Target Disk Mode, connect it to the laptop with the right cable, boot the laptop off of the Usb installer, and then do a fresh OS install onto the iMac through the laptop.

You should also take a look at this thread and see if any of its suggestions help:

Big Sur crash

After latest update on MacBook Pro 16 inch , it boots...logs on and crashes to dark screen. Your hear the fan Rev fast for one second , then it reboots Crash log says this panic(cpu 9 caller 0xffffff800189dc5a): "Inconsistent OOL/copyout size on 0xffffff86e59a7ba0: expected 44, got 0...

forums.macrumors.com

 

[PatiPhillips]

Since you have an extra laptop running Catalina, you should be able to boot your iMac into Target Disk Mode, connect it to the laptop with the right cable, boot the laptop off of the Usb installer, and then do a fresh OS install onto the iMac through the laptop.

You should also take a look at this thread and see if any of its suggestions help:

Big Sur crash

After latest update on MacBook Pro 16 inch , it boots...logs on and crashes to dark screen. Your hear the fan Rev fast for one second , then it reboots Crash log says this panic(cpu 9 caller 0xffffff800189dc5a): "Inconsistent OOL/copyout size on 0xffffff86e59a7ba0: expected 44, got 0...

forums.macrumors.com

I tried all of the fixes from that forum but none worked for me. My computer will not boot into safe mode.
I just purchased a cable that will work from laptop (mac book air) to my mac but I am unsure of the process. Are you saying, connect my laptop to my mac and then boot into "choose boot disk" and choose the laptop to boot up? If so, how do I get the OS Catalina installed onto my mac? I am not all that savy in fixing computers, just using them. Have been trying to get a bootable installation usb thinking that was the way to go. I was able to get into my mac and had the option of installing Catalina but after downloading it through recovery mode, it said it could not be installed as my computer needed some updates. Not sure what that means. I ran big sur fine until this latest update.

 

[PittsDriver]

Sounds like your only option is a wifi recovery.

 

[PatiPhillips]

Trying that right now. Keeping my fingers crossed. Spent two days trying to fix this. I am so disappointed in Apple releasing this too soon. I have touted their greatness for years. Partly my fault though, should not have put a beta on my work computer!

 

[russell_314]

Trying that right now. Keeping my fingers crossed. Spent two days trying to fix this. I am so disappointed in Apple releasing this too soon. I have touted their greatness for years. Partly my fault though, should not have put a beta on my work computer!

Apple releasing this too soon? You realize Big Sur is only released for beta TESTING. I always tell my friends PLEASE don't install a beta OS on anything you need to use. It's for if you have an additional computer or phone just for testing purposes. I wish you luck and hope the restore works

 

[minifridge1138]

1 - Create a bootable Catalina install drive.
sudo /Applications/Install\ macOS\ Catalina.app/Contents/Resources/createinstallmedia --volume --downloadassets /Volumes/MyVolume

WARNING - this will delete all data on /Volumes/MyVolume. Replace this value with the USB thumb drive.

Create a bootable installer for macOS - Apple Support

Use an external drive or secondary volume as a startup disk from which to install macOS.

support.apple.com

2 - With the iMac off, plug in the USB thumb drive that you configured in step 1.
3 - Reboot the iMac and hold the 'OPTION' key until you see a list of bootable drives.
4 - Select the Catalina Installer.
5 - Go through the normal OS install steps.
6 - Restore the iMac from your most recent backup (you do have a backup, right?)