An error occurred preparing the software update - Big Sur

Hello!

So I have the same issue and I am trying to follow the steps you suggested.

Now I have not backed up my Mac. So I would just like to confirm, erasing or unmounting the update will not result in any loss of data?

Also, when choosing erase in disk utility, it asks to select a format:

• Mac OS Extended (journaled)
• Mac OS Extended (journaled, encrypted)
• Mac OS Extended (case sensitive, journaled)
• Mac OS Extended (case sensitive, journaled, encrypted)
• ExFAT
• MS-DOS (FAT)

Now I’m not too sure which format I should be choosing? Is it better to just unmount than erase?

thankyou!

Thank you for your help!

I have now unmounted it.

I have tried running ‘first aid’ however it says that it has failed and if possible to back up the data on this volume. This was due to:

• verifying storage system
• storage system check exit code 8
• repairing storage system
• storage system verify or repair failed
• operation failed

now I’ve tried to continue and click ‘run’ as instructed in the top left menu, however I unfortunately do not seem to have this button/option?

Thanks again for your help!

Its much appreciated

Everything worked until I got to this part below in your suggestion. There is no run feature to select in the left menu. Can you be more specific regarding what you mean by run or what you clicked in the left menu? Thanks

• Now I run the disk ‘Macintosh HD’ by selecting and clicking on the run option via the top left menu. Be aware i had another disk greyed out ‘macintosh HD-data’, which I haven’t touched. A prompt appears where you have to ‘unlock’ the disk. You will ask to insert your password (this time it works!). The system will reboot and voilà. All my files were there!

In the case of my mac i had no space to inicialize so the support told me i need another mac to pass my data onto (do the target disk mode), then erase it all and download the macOS

but maybe for others this might work:

1. press the on/buttom and release
2. than hold option command R until a « world » appears

other option the suport showed was:

1. press the on/off buttom and release
2. than hold option command P R until the computer makes 3 times the sound
3. release the 4 buttons
4. it should appear 4 options, select the one that says install mac Big Sur
5. if you have enough memory it might work

Hi Sören

I thrown away the paper where I noted all the steps I think. I am away from home currently and just have my ipad with me. From memory though🤔 this is what I remember. If you can’t install Big Sur yet, dont worry because it will be a long tedious task and depends a lot from your internet speed too and the firewall on the router. Switch it off. That’s the first point I want to make.

It took me at least two afternoon to solve the problem. That’s how tedious it can be so be patient.

• Restore your current version of MacOS and create a backup on an external hard drive. (I was lucky enough to have a spare one of 1TB)
• format your external hard drive first and wipe it off before, rename it “Backup”
• Once your computer is backed up go to disk utility and erase and format your HD drive on your computer (format it to MacOS journaled I think)
• Once done, go back to MacOS utility and select install MacOS via internet is you dont have the disk
• One important thing to remember. If passwords don’t work it’s probably because you have more than one account with Apple. So choose the one you use the most often. If you have a smartphone, reset your password on the most use Apple account and when prompt for your password on Apple Store for updating; you password should be accepted. Also the way you will login to your computer will change too. With BigSur , to log in on your computer they will ask for your Apple account password (the one you just changed), it wont be an admin password. I suppose you can change this once you are log in the computer, personally I didn’t as I’m the only user.
• Once MacOS installed, search for update and leave the computer updating to the last version of MacOS. It might go straight to Big Sur.
• Once Big Sur is installed, restore your backup by choosing the files you want back on your computer.

Hope this helps. I had no issue updating Big Sur since installed apart being lengthily due to living in rural area and having a crap wifi.

I will be back home on Monday so I will look for the paper with my notes. Meanwhile try these steps over the weekend and be patient. After all this pandemic recommend us to stay at home, so lets get occupied while staying safe 😉

I wish everyone best of luck

Hello all, I had this same problem, and I was able to mostly recover my data, hopefully this is helpful for some of you!

What I did:

1. After I got the message that the install failed, I clicked the thing that said restart in targeted disk mode.
2. connected it to a second Mac with thunderbolt cable
3. For some reason, it wouldn’t accept my password when I try to mount the drive on the second computer. It also rejected the password in the recovery mode that others suggested.
4. Downloaded Disk Drill software. This scanned the drive and showed all my files! My password worked fine for this software (who knows why!). The free version let me see the files, but then I had to pay $97 for the “pro” version to recover the files. They’re mostly there. Some of the older files are broken or something, they won’t open. But better than nothing!
5. Restore computer from scratch. Haven’t done this yet, should be pretty straightforward, but who knows, it may be a nightmare!

P.S. Apple-why did you do this to me? My weekend was ruined and my wife won’t speak to me after I almost lost all of her files. All for a stupid os update, ugh.

I was FINALLY able to resolve this, without wiping my hard drive and losing all my data. You need another computer running OSX 10.13 or 10.14. Here's the steps I followed (big thanks to https://mrmacintosh.com/big-sur-upgrade-not-enough-hd-space-serious-issue-possible-data-loss/)

1. Plug problem laptop into desktop with thunderbolt cable, laptop in Target Disk Mode
2. Desktop is running 10.15 Catalina. In Disk Utility, I see "Macintosh HD - Data - Data" which is the folder I need to access, but when I click Mount and enter my password, it is rejected. This is a problem with Catalina..
3. Download OSX 10.14 Mojave
4. Using the third party software DiskDrill I turned Flashdrive 1 into a bootable install disk of Mojave.
5. Restarted Desktop holding Option key. Clicked install Mojave. Installed on 64GB Flashdrive 2.
6. Booted from flashdrive 2.
7. Opened Disk Utility, Laptop in Target Disk Mode, mounted Macintosh HD - Data - Data. Password works now!
8. Deleted a bunch of files until I had over 30 GB free.
9. Restarted Laptop, install finishes successfully!

I had the same exact error: I tried installing Big Sur with about ~15GBish but apparently you need ~35GB to actually install it. After the error "an error occured preparing this update" appeared --> i shut it down and turned it back on --> just goes back into the normal login page --> mac tries to install Big Sur again and fails --> "an error occured preparing this update" --> endless loop

I fixed it after spending close to a week working through a bunch of trial and errors!

Here's what I've tried that DIDN'T work:

• internet recovery
• "normal" recovery: my password wasn't accepted even though it's 100% correct and the option to recover via the apple iCloud wasn't successful (tells me that my iCloud account can't be used for my mac...)
• resetting the SMC
• resetting the NVRAM

Here's what I did that WORKED (at least for me):

1. Started up this mac in the Target Disk Mode (shut down the mac and press T to go into this mode)
2. Connect this mac to another mac with the thunderbolt cable
3. Start the other mac (i.e. working mac) in recovery mode --> go into disk utility --> attempt to unencrpyt the hard drive of the mac that's having trouble (I can't remember if my password was accepted then but I don't think so)
4. Start your working mac in a normal manner --> login --> you will be prompted to type the password for the hard drive of the mac that's having trouble. They accepted my password finally (and any prompts from here onwards accepts my correct password)! Now delete some stuff in the hard drive of the mac that's working! I deleted some applications that are easily downloadable from the internet/are free until my drive had about 58GB of free space (no specific reason why I freed 58GB - I just wanted to play it safe). Eject the hard drive.
5. Start up the mac that's not working in recovery mode! The recovery mode should now be the "normal" recovery menu with the 4 options (use Safari, choose disk utility, time machine, reinstall Big Sur). I chose the reinstall Big Sur option and it redownloaded BIg Sur and then installed it later. AND IT WORKED. I WAS ABLE TO LOGIN INTO MY MAC AND SEE ALL MY ORIGINAL FILES BACK PHEW.

Let me know if you need any clarification. I'm more than happy to help because I know how it feels to be stuck troubleshooting for what seems like infinity and be anxious about losing all of your files. Ping me if necessary!

Apple personnel aren't here. We're all users like yourself. If you want to talk to Apple call the number at the bottom of this page and ask for Customer Support.

Make sure you don't have a file in the Applications folder titled "Install macOS Big Sur.app". If you do then delete it, wait a day and try again.

I tried doing this and everything is well after selecting the other option for the Mac which leads me to my login screen. After entering my password, there’s a loading bar for about 5 minutes and then all of the sudden the entire screen turns black and the prohibitory symbol pops up.

Hello!

I'm having the same issue as septi32> shutdown-press option, the process only repeating the same, need advise please.

What does "restoring from backup" means?

Does anyone know details for the "target disk mode" option?? (can I put all the data from the macbook air to a 2010 macbookpro whitout loosing my computer stuff? if yes, which cable should I use?)

I had also got to the disk utility window by turning on the computer with option+command+R, like palma86

advice, but not sure how to follow from there, because there is nothing is grey locked like the description of his case.

I don't have any backup of my computer stuff and I'm scared to make a bad move and erase all!!

Sorry for so many questions, I'm new in this kind of support community websites, please, help! Thank u!!!

Hi, i’m also having the same problem. I have already shutdown > held option while turning on then it asks to choose the wifi network, apears « mac installer » only, after clicking it starts loading for 29 minutes than the following images apear over and over

and it never gets out of that screen.

has anyone been able to get out of it without erasing the mac? (I dont have a backup)

if anyone could help with the step by step, i would aprecciate, thanks

Okay I had the same basic experience

I was running MacOS Mojave and it was running well no complaints but I don't like to get to far behind so I ran a time machine backup first unencrypted.

Then ran the update to MacOS Big Sur

I got the same error "An error occurred preparing the software update"

Tried recovery mode but that did not work as it would not unlock the drive with the correct password (this is troubling and makes me question file vault ) I also tried using my apple ID to unlock the drive but this did not work as it could not unlock the drive.

Tried Safemode but that would give me the dreaded Circle with a line in it

I figured out it was most likely due to lack of storage space. Then found this post.

This is what I did.

I used a MacOS Mojave usbkey installer (I made a while back)

I install MacOS Mojave to an external drive (Nvme SSD usb c drive)

after successfully booting to the external SSD drive

I then was able to unlock my internal drive (the password worked) and I remove 50 GB of data

Then shutdown disconnected the external SSD

Then rebooted to the internal drive and the install of Big Sur Finished

I know I should have looked at the requirements prior to upgrading.

I would hope in the future the Installer for all MacOS Updates checks to make sure the system meets the needed space requirements.

Hope that helps.

Brian

I have this same problem and I don’t not have any other computed to connect it to in order to use target disk mode. I don’t know what to do because every time I restart/shutdown and turn on the computer it comes up with the same error. I believe I have a 2018 MacBook Pro. I do not know what else I can do at the moment. I am also a college student and need my computer for classes so this is a huge problem at the moment...

I have the EXACT same problem as you have listed. I have a MBP 2019 13' 2port.

I even tried reviving BridgeOS via using apple configurator 2. That didn't work out as well.

I would suggest we move this discussion on to the developer forums for more technical talk, this problem has been causing massive inconveniences for me and Apple needs to know about this.