An Error Occurred Preparing The Software Update – Macbook Pro


I am detailing my journey through this update on my Macbook Pro so that it can help others.

an error occurred preparing the software update

2019 MacBook Pro 2.3Ghz, Upgrading from Catalina to Big Sur.

The process…

  1. Big Sur downloads
  2. restarts then tries to install and gets stuck at 10%, giving the error you see below
  3. Trying to start in recovery then asks for your password, which the Mac tells you is incorrect
  4. Trying to enter your vault key from iCloud doesn’t work either because it tells you your “iCloud account cannot unlock this volume
  5. There is no way to get to a main screen or any screen; no way to recover or enter your password for anything
  6. Spent 2 hours on the phone with Mac support: we finally were able to to get it to a Utility screen by pressing “Shift + Option + Command + R” at the same time immediately after hitting the power button, wait a long time for it to start up; where you will see a world icon with a bar or timer under it; took about 15 minutes
  7. In the utility screen settings, when they finally appear after having to re-enter your password for your Mac; and I found out what was wrong; my Macbook didn’t have enough space; you can see in the below screenshots
  8. Big Sur is 13GB. My Macbook Pro had 9.5GB of free space; normally, Big Sur would not have downloaded knowing it didn’t have enough space… but that didn’t happen, so it tried to install itself anyway, and got stuck
  9. Now, there is no way to clear space; the hard drive section in Utilities is missing so we cannot reset the OS (Operating System) to an older version
  10. Apple Support said take it to an authorized Apple Repair shop; so I did
  11. Took it to a Mac specialist locally and they said they have no idea how to fix it; but they would have to wait 3-5 days likely at minimum before Apple released a resolution, also a lot of people are having this issue
  12. You need your laptop for work or school, so this is debilitating, I feel you.

Connecting Your Mac To Another Mac For Recovery

You can try this; but both Macs have to be the same hardware/version.

starting recovery mac to mac

The Supplied iCloud Account Was Unable To Unlock This Version

“If you can’t log in to your computer because you forgot your password, you can reset it now”.  Trying to recover your Mac using your iCloud account will not work either, it just gives you this error message.

the supplied icloud account was unable to unlock this volume

Using MacOS Utilities To Restore from Big Sur Update To Catalina or Earlier Version

  • Time Machine – this only works if you had been saving everything you do on a backup device, like a second hard drive that you attached to the Macbook. If you haven’t been, this is not going to work.
  • Reinstall MacOS – It fails; but if it works it means you lose everything not saved in the cloud or on a backup drive
  • Disk Utility – It is not showing the necessary hard drive in order to clear space or reset the OS (Operating System)

Go to Utility screen by pressing “Shift + Option + Command + R” at the same time immediately after hitting the power button, wait a long time for it to start up; where you will see a world icon with a bar or timer under it; took about 15 minutes and it brings you to this….

macOS utilities not working for recovery big sur

Not Enough Space For The Big Sur Mac Update

So, I finally found out that the reason Big Sur is not installing is because there was barely enough space. However, there is no way now to clear the space. I am at risk of losing anything that wasn’t saved in the iCloud now.

not enough space for mac update

Resolution So Far (Nov 20th, 2020)

Had to take it to a Mac repair shop, Mac Phone Support could not figure it out; the Mac repair shop needs 3-5 days minimum. I am looking at buying a replacement Mac in the meantime. The new Mac M1 chip laptops seem like a good choice, and to have a backup back for future issues.



IreneDecember 7, 2020 at 5:49 amReply

Did you fix it? I am currently going through the same thing and need it for finals week.

Thomas JDecember 8, 2020 at 1:11 pmReply

I am afraid not. It tore the hard drive, I lost everything that was saved to the drive; fresh install after a week of the shop trying, like a new laptop. I lost a LOT of data.

Emma LitvinovDecember 25, 2020 at 8:51 pmReply


I had the same issue and solved it in this way:
– From internet recovery (spinning world icon) (cmd+alt+r) : go into disk utility (same screen as you’re showing above). Erase the “Update” disk container as shown in the picture above, and any other disks that are not the one your information is stored on (the ones that are not greyed out) (you can tell by seeing how much space is occupied on each disk). Also, try running first aid on all of them, you might be able to see more information. You erase and delete them by pressing the “-” in disk utility. In my case, I had 3. One was “Macintosh HD”, the other “Macintosh HD – Data”, and the third “Update”, like you. My “Macintosh HD – Data” was greyed out. So I deleted “Macintosh HD” and “Update”. The one named “Macintosh HD – Data” had the most information on it so it had to be the one I had my files in. You do not have to delete anything under “Disk images”, only under “Internal”.
– After doing this, I pressed “first aid” on the disk that was greyed out/locked. In my case, it was Macintosh HD – data, it asked me to enter in my password and this caused the disk to UNLOCK!!
– After this, I was able to reinstall Catalina on that disk (from previous picture) “Install MacOS”. And it worked!!

Now my computer is running on Catalina as before and all my files are intact. I tried to install Big Sur again after freeing up 47 GB of space and still, the same thing happened. So it might actually not be because of the space problem..

For now I’m just going to continue using Catalina since it works great and hopefully wait for the next update to be released, perhaps it will be easier to install than this one..


Thomas JDecember 27, 2020 at 2:24 pmReply

Eventually; my hard drive got lost and unrecoverable. It had to be wiped, I lost 2GB of data 🙁

Thank you for sharing this. Now I just save everything to the cloud.


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