I'm trying to create a Big Sur installer flash drive. All the tutorials tend to gloss over how to download the installer, but I'm finding that since this Mac is already upgraded, I can't download it again. How can I get ahold of the installer file? Only looking to download from Apple, not a third party. Thanks!
How to download the macOS Big Sur installer on a Mac which is already running Big Sur
big surbootable-diskinstallusb
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Best Answer
Using a clean install of macOS Big Sur and then attempting to download the macOS Big Sur installer on the running occurrence of it, I was unable to do it using the methods described in the answers by bmike and Nimesh Neema in this thread.
I then tried using Terminal and the
softwareupdate
command:I got the same "Update not found" error message as with the other methods.
What I tried next was to use the third-party python script that downloads the various packages directly from Apple's servers and assembles them into the installer app.
Note that I did not completely download it as I already have the installer and no need for the to download it again at this point, however the fact that is was downloading the packages, including the biggest one which was 11.3G in size, I'll assume the script will finish correctly as this script has been available on the Internet and in use for some time now and ifs still being maintained.
Using the
installinstallmacos.py
python script from GitHub:In Terminal I change directory to where I download the extracted macadmin-scripts-main.zip and executed is as:
A bunch of stuff scrolled on the screen to stop at:
I chose
10
and it proceed to download the packages directly from Apple's servers.While in Terminal you will see exactly what it's downloading and see it's coming directly from Apple's servers.
Assuming it's going to create the /Applications/Install macOS Big Sur.app application bundle, you would then use the following command in Terminal to create the installer:
Changing
MyVolume
in the command to the actual name of the volume of your USB drive been used for the installer.See How to create a bootable installer for macOS for additional details.