An error occurred preparing the software update - Big Sur

I tried restarting while pushing the Option button but I did not have the Mac HD option. It only says Mac OS Installer. So now I just keep coming back to the same error. I wanted to just go back to my old OS and free up space before updating but now I can’t do that anymore. I don’t have a recent back-up so I hope to just go back to my old OS. Help!

Please help me. I am having the same problem. Managed to boot up using the external SSD with Big Sur installed, but I cannot delete any files from the Macintosh HD.?!? How to avoid losing all my previous data in the Macintosh HD?

I couldn’t agree more. I went through almost all the same things and in order not to loose everything I have, they told me to go to an authorized store and do the procedure there, what will cost me money, which is not correct since this problem was not a result of something I did, it was indeed due to the update to BigSur.

Trying to do the Bug Sur installation today and getting the error message of "an error occurred preparing the software update". Tried a couple of times, then deleted and re-downloaded the app "install Big Sur MacOS" from the Applications folder. No impact.

I am able to restart the computer holding down the option Key and selecting the original SSD, which had been renamed with a "-Data" on the end of its original name.

I've read all 13 pages of posts on this thread and most have dealt with the problem that >35Gb of free space is needed. That is not my problem as I have >250 Gb available.

I am trying to avoid the hassle of a SSD wipe and rebuild (I do have a recent Time Machine back up). I have a USB Mojave installer and can create a USB Big Sur installer if need be.

I'm not quite sure on the next logical steps so any simple advice or URLs would be appreciated.

Tracy

MacBook Pro, mid-2015, Mojave, i7/2.8 GHz processor, Mojave, 16 Gb ram, 2Tb SSD

Hi Soren and thx for reply.

I got the BS installer through the Software Update pane in Systems Preferences.

I am currently running Mojave, 10.14.6.

I will try re-downloading the BS installer from the App Store. I'll first try an install using that and it fails, I'll create a bootable USB.

Funny you ask about software updates . . . I did not update the recent Mojave Security Update or the Safari 14.03 'cause I assumed it would take care of itself under Big Sur. Are you suggesting that I update those items before attempting another BS install?

Believe me, it all helps. I ran out of ideas short of a clean wipe.

Hi Tracybjazz,

Just checking in to see if the suggestions helped and if you were able to install Big Sur successfully and which method helped, the link I shared or booting directly off the USB installer.

If you have any issues don't hesitate to write back.

Hi Soren. . . . . I tried to install used the link's download installer. It got further along in the install process (had ~12 minutes to go) but it eventually stopped with the same error message that started this thread. I tried twice but stopped at the same point. I just finished creating the bootable USB installer and I'm minutes away from that install attempt. . . . Most of my time this morning has been spent making additional backups for items that I do not want to lose. Just in case Mr. Time Machine back up fails me during a disc wipe and clean install . . . . ;-). . .. . I'll will let you know. . . thx for checking . . .. Tracy

Just completed the install attempt using the USB installer . . . . same error message only this time, I was stopped at 29 minutes into the install. I may try one more dL of the installer itself with the USB approach . . . . what was that old saying about the definition of insanity? ;-)...... thx . . . Tracy

Hey Soren . . . . oddly, the MBPro will not let me boot in Safe mode . . . I get the symbol for 'not allowed'. . . . . so unless you've got any more rabbits in your hat, I think I've exhausted my options for getting Bug Sur installed. It may be time to start researching a restore from Time Machine (mine is on a NAS drive) or a completely fresh install of Mojave. . . thx . . Tracy

Hi Soren . . . Yes, for "not allowed", I meant the circle with the diagonal line.

I tried the 4 things . . . . 1-2 had no discernible effect. Disk First-Aid was fine.

For suggestion 4, I can start up in recovery mode (Command-R) but the only choice for OS is Big Sur, which will probably end up in a clean install/drive wipe, if it is able to complete the install, which I doubt.

There is another start up key combination (Command-R-Shift-Option) that should allow me to install the OS that came with my system (or close to it) but alas, I get the "not allowed" symbol.

I have a USB bootable Mojave around somewhere. I may dig that out and see how the MBP responds.

Thanks again for your help/suggestions . . . . but I think we are running out of options. I suppose I could call Apple or even stop by the Genius Bar but that will probably result in several hours of deja vu.

rgds . . T

Hi Soren . . . the mystery keeps unfolding. I wiped the internal drive and installed a fresh Mojave. I then installed the latest Mojave updates. All installed just as expected. . . I then tried to dL Big Sur (3x) first through the Sys Pref Software update but then through the link (to the App Store that you provided). . . . but kept getting an error message at the very end of the 1-hr dL, which basically said something to the effect BS could not be verified - an error occurred while installing the BS updates. . . . Then when I do a Command-R restart, the macOS installation option shows me only a reinstall Mojave. The BS install option (that I thought should be there) is not an option. It's my MPB will do anything to avoid BS . . . . any suggestions? Maybe another complete drive wipe install? . . . thx . . Tracy

Hi Soren . . . that's a reasonable suggestion except that I outsmarted myself. I deleted the USB BS installer and replaced it with a USB Mojave installer, in case there was an issue during the wipe and clean install of Mojave via 'recovery' mode. . . . . . Regardless, I'm ready to move in a new direction: clean install Mojave > Time Machine restore > Catalina. . . . .. I've been a Mac user since 1989 and I've never had this much trouble with an OS upgrade. OS9 to OSX was a cakewalk compared to this . . . . thanks for all your suggestions. . . kind rgds . . T

Yea, Im having the identical issue...have spent hours on with Apple support, they also have no clue how to resolve

I am facing same issue while upgrading from Catalina to Big sur - MacBook Pro 2019. Even I cannot reboot in safe mode. Safe mode reboot is not working. Kindly suggest.

I have the exact same problem since yesterday. Has anyone been able to solve it? I definitely can’t afford to lose my data since I don’t have a recent backup