My iMac will not install the latest upgrade to Big Sur. Is there something I need to configure to get it installed?

Revision # 5 - April 19, 2021

Tips How to Upgrade to Big Sur 

There are several points to consider before attempting the upgrade to Big Sur. The most important is Due Diligence on the part of the User and is a Prerequisite for a smooth upgrade.  

The below points should all be consider Before attempting the upgrade.

Point # 1 - There are unconfirmed reports that upgrading from earlier version of macOS will download a " Stub " of Big Sur. This " Stub " maybe about 25 MB is size and is not the Full Installer. If so, run this Application and it should pull down the remainder of Big Sur and commence the Installation

Point # 2 - Are there pre-existing Unresolved Software Issues. They should be resolved prior to upgrading - they may carryover to Big Sur making the system unstable / unusable.

Point # 3 - Are there any AntiVirus, Disk Cleaner, Optimizers, Defrag, VPNs etc installed which should be removed as per Developers Instructions. They are useless, unneeded, cause havoc and interfere with the normal operation of the OS and may even Corrupt the OS requiring a Reinstallation. The Built-in Security of Big Sur is all that is required.

Point # 4 - What are the System Requirements ie: Empty Space Requirements specific to the Big Sur.

Point # 5 - Does the intended computer qualify for the upgrade.

Point # 6 - Are the installed Applications / Extensions compatible with Big Sur. Check with the Developer for compatible Apps / extension or do they offer updates. Same goes for Third Party Drivers for Printer, Scanners etc.

Point # 7 - If upgrading from Mojave and earlier versions of macOS - Remember that Big Sur does not support anything 32 bit. These include Applications, Extensions and Drivers for any devices.

Point # 8 - Do I have a Rescue Plan In-Place. This comprises having a Time Machine Backup and for addition purposes - two Tested Bootable Clones each to separate external drives. This is insurance incase the upgrades goes sideways

Point # 8  - To upgrade to Big Sur will require a quick, stable and reliable Internet Connection - preferred method is via Ethernet Connection. If not available and using Wifi - move computer as close to the Access Point / Router and disconnect all other devices connected to Wifi. Want the maximum bandwidth for the computer being upgraded to Big Sur.

Good Luck and come back to these Forums if there are questions, concerns or comments.

If the ethernet solution fails try the following (keep the ethernet connection):

1 - boot into Safe Mode according to Start up your Mac in safe mode - Apple Support.

NOTE: Safe Mode boot can take up to 10 minutes as it's doing the following; 

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files

2 - go to the App Store and search for and download Big Sur. It will be the full installer so will be ab out 12 GB in size. Be sure you have at least 20 GB of free space on your boot drive.

3 - run the Big Sur 11.2.3 installer.

I've had better luck going thru the App Store than thru the System/Software Updates preference pane.

Your Mac may be too old for Big Sur, but it's not possible to comment without knowing exactly which model it is.

Click the Apple menu at extreme left of the menu bar and chose 'About This Mac'. Click 'System Report' (this may be worded differently on some Macs). Alternatively open 'System Information' in Applications/Utilities.

In the pane which opens, the second line, 'Model identifier', contains a number, e.g. 19,1. Post this here. Don't post your serial number.

In the meantime, you should be aware that any applications you have which are 32-bit will not run in Big Sur. If you open the 'Software>Applications' section of System Information there should be a column for '64-bit': and application which says 'No' here won't run in Big Sur.

Sorry but think you have misquoted about removing the Stub. Please re-read. The Stub was an old way Apple sometimes would deliver the UpGrade and at the same time - would not allow the user to Create a Bootable Installer as it " Stub " was not a complete version of the New OS

" Point # 1 - There are unconfirmed reports that upgrading from earlier version of macOS will download a " Stub " of Big Sur. This " Stub " maybe about 25 MB is size and is not the Full Installer. If so, run this Application and it should pull down the remainder of Big Sur and commence the Installation "

Item #1 - Remove the "stub" - which application were you referring to?