Failed to prepare the software update for macOS Big Sur Beta 6

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Created Sep ’20

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Can't install macOS Big Sur Beta 6 on MBP 16". After 100% downloaded it always says "Failed to prepare the software update. Please try again".

I've reseted NVRAM, disabled FileVault, enabled full Secure Boot — nothing helps.
Total OS reinstall from recovery mode fails too.

Here's terminal log from command

Code Block sudo sh -c "softwareupdate -ia"

Finding available software
Downloading macOS Big Sur Beta 6
downloading: 100.00%
Failed to download & prepare update: Error Domain=SUMacControllerError Code=7740 "[SUMacControllerErrorPrepareFailed=7740] Failed to perform Prepare operation: [MobileSoftwareUpdateErrorDomain(MSU):MSUERRFILESYSTEMDOESNTVERIFY(3)1MobileSoftwareUpdateBOMErrorDomain:1|FullReplacementRequired|]" UserInfo={SUMacControllerErrorIndicationsSummary=|FullReplacementRequired|, SUMacControllerErrorIndicationsMask=2, SUMacControllerErrorIndicationsDescription=-> Full replacement is required [as opposed to incremental patch]., NSUnderlyingError=0x7fcd600040e0 {Error Domain=MobileSoftwareUpdateErrorDomain Code=3 "'./System/Applications/App Store.app/Contents/Info.plist' did not verify and is not on the exception list." UserInfo={targetupdate=20A5364e, NSLocalizedDescription='./System/Applications/App Store.app/Contents/Info.plist' did not verify and is not on the exception list., NSUnderlyingError=0x7fcd60004270 {Error Domain=MobileSoftwareUpdateBOMErrorDomain Code=1 "contents of '/System/Volumes/Update/mnt1/System/Applications/App Store.app/Contents/Info.plist' don't match bom (71809a08 vs 8a7b320a)" UserInfo={NSLocalizedDescription=contents of '/System/Volumes/Update/mnt1/System/Applications/App Store.app/Contents/Info.plist' don't match bom (71809a08 vs 8a7b320a)}}, MSUFullReplacementRecommened=true}}, NSDebugDescription=[SUMacControllerErrorPrepareFailed=7740] Failed to perform Prepare operation: [MobileSoftwareUpdateErrorDomain(MSU):MSUERRFILESYSTEMDOESNTVERIFY(3)1_MobileSoftwareUpdateBOMErrorDomain:1|FullReplacementRequired|], NSLocalizedDescription=Failed to prepare the software update. Please try again.}

What else can I try?

Answered by dontliem1 in 635676022

I've finally defeated it by full OS reinstalling from recovery mode (Cmd + R).
Don't know what exactly has been messing with this method previously, here's what I tried:

I removed password from my wi-fi, changed its MTU to 1450 and change DNS to 8.8.8.8 and 8.8.4.4
I booted from Option + Cmd + R to update by internet — It downloaded Catalina and couldn't install it because there was no suited disk.
I rebooted in recovery mode (Cmd + R), used a First Aid in Disk Utility on all disks and then clicked reinstall OS and put Macbook on a table charging all night.
In the morning there was Beta 7 installed already and there was Beta 8 waiting in Update Center. It installed without problems.

Hope something of this would help someone.

Boost

Answer 1

dontliem1 OP

Sep ’20

Accepted Answer

I've finally defeated it by full OS reinstalling from recovery mode (Cmd + R).
Don't know what exactly has been messing with this method previously, here's what I tried:

I removed password from my wi-fi, changed its MTU to 1450 and change DNS to 8.8.8.8 and 8.8.4.4
I booted from Option + Cmd + R to update by internet — It downloaded Catalina and couldn't install it because there was no suited disk.
I rebooted in recovery mode (Cmd + R), used a First Aid in Disk Utility on all disks and then clicked reinstall OS and put Macbook on a table charging all night.
In the morning there was Beta 7 installed already and there was Beta 8 waiting in Update Center. It installed without problems.

Hope something of this would help someone.

0

Answer 2

KiwiBird97 OP

Oct ’20

If a problem occurs, you may want to run the full installer.

Redownload the macOS Developer Beta Access Utility and run it.
Once the utility has finished running, select to keep the installer. This can be run as many times as needed in case a problem occurs.
The App Store will open showing the Big Sur Beta. Select GET.
Select Download at the prompt to start the recovery process. This 12 GB download may take about a few hours to complete, and you will still be able to use the computer until the installation is ready.
You will need approximately 35-50 GB (or even more) to install the update. Free up space if needed.
Click Restart to begin the update. Your computer may restart more than once during the installation. Please do not turn off the power until the Setup Assistant appears.

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