After trying and failing many restarts since Big Sur bricked my late 2015 iMac, the only option appearing on the screen is to Restart in target disc mode. Will doing so allow me to revive Catalina? My only backup is iCloud and the only Apple store in the area closed on 2020.
iCloud is not a backup!!!!!!!!
Time Machine, a bootable clone or an online service is backup. Operating ANY computer without a backup plan is dangerous and is a 100% guarantee of lost data.
First I would recommend that you shut down the computer, then restart while holding down the power key for about 15 seconds. If that does not work, reset the NVRAM and restart in Safe Mode.
If all else fails, your best bet is to restart in the Recovery Partition (Hold down Command + R keys on startup) and then install Mac OS.
After you have cleaned up the situation you are in, please create a backup. To begin I would recommend Time Machine which is pre-installed on your computer and only requires an external HD such as one the following OWC Mercury Elite Pro , the HD should be about 2-3 times the capacity of your storage amount. If you have never heard of Time Machine or are not familiar with it, please look over Back up your Mac with Time Machine
Good luck!
Don't Panic!
Peaches; I had the exact same situation as you, and I am an everyday user with no programming skills. It CAN be fixed; and I did not lose ANY documents or data. Someone on this thread, rkaufman87, told me how to restart in Recovery Mode (Recovery Partition). It worked perfectly and allowed Big Sur to finish downloading. Read his comment above for the directions I followed.
THANKS tkaufman87! Recovery worked. It finally downloaded Big Sur and it looks like I didn’t lose anything.
My iMac has 1 terabyte of available storage, but I’m only using 23% of that after 5 years. Do you think a 1 terabyte backup HD will be sufficient?
1TB should be sufficient as most experienced users recommend a Time Machine External Hard Disk that is 2-3 times the size of the amount of data it will be backing up. So if you don't anticipate the amount of data to grow that much then you should be fine.
I updated iMac from Catalina to big sur. Restart has frozen and won’t open, no option available except for turning power off and turning power on (taking plug out and back in). Will not reboot, takes me to screen that gives me one option to restart disk using another computer!
HELP -
Screen
yellow warning sign
with frozen icon
message underneath says
AN error occurred applying the software update
blue message OK
PLUSH OK
message comes up
Click to restart this computer in target disk mode
after you restart this computer in target disk mode, you can connect it to another computer using a Thunderbolt cable and use it as a disk drive.
I am an end user, feeling nauseous have all business docs in iMac. Need to access. Please can anyone help me?
It appears my iMac won’t restart in safe mode. This concerns me. I have no confidence in my ability to go further. Have contacted Apple Care who said the same words ‘don’t panic’ bring the iMac in for Apple to investigate. If it had gone into safe mode different story. Thanks again for replying and helping. Fingers and toes crossed it can be recovered and back working. Cheers
If you can bring it to an Apple store; I'm sure they'll be able to fix it. I would have done that too, but the Apple store where I live closed last year.
Safe mode didn't work for me, either. But when someone told me how to restart in Recover Mode, that did it. I had my fingers crossed the whole time also; the Apple Store will be less pressure. Good luck.
Crash while installing Big Sur
