How to Make a Bootable macOS Big Sur USB Install Key [Video]

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Posted November 14, 2020 at 12:24am by iClarified

These are instructions on how to make a bootable USB install key for macOS Big Sur.

Step One
Connect a 16GB or larger USB flash drive to your computer then launch the Mac App Store from your dock.

How to Make a Bootable macOS Big Sur USB Install Key [Video]

Step Two
Navigate to the macOS Big Sur application page and click the Get button.

You may be brought to a Software Update window, click Upgrade Now or Download to begin downloading the update.

Once the installer launches, press the Command+Q keys on the keyboard to exit.

Step Three
Open your Applications folder and select the 'Install macOS Big Sur' app. Press Command+i on the keyboard and verify its size.

If it's over 10GB, skip to the next step. If it's tiny (~20MB), you can either run it to install macOS Big Sur and then redownload the installer, or delete it, upgrade to the latest version of Catalina from the Mac App Store, then redownload the installer.

Step Four
Once you've verified that you have the full installer, launch Terminal from the Applications:Utilities folder.

Step Five
Note the name of your USB key.

Execute the following command in the Terminal window replacing 'Untitled' with the name of your USB key. Please note this will erase the entire USB key.

sudo '/Applications/Install macOS Big Sur.app/Contents/Resources/createinstallmedia' --volume '/Volumes/Untitled'

You will be asked to enter your Administrative account password.

Type Y and press enter to begin.

Step Six
If prompted to allow Terminal to access your removable device, click OK.

After about 30 minutes the creation of your USB Install Key for macOS Big Sur will be complete.

Step Seven
You may now restart your Mac and hold down the Option key after hearing the boot sound. You'll be presented with a list of bootable drives. Select the USB install key to begin.

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Johan85 - November 25, 2024 at 2:18pm

hi. how can I getAdministrative account password? need to install big Sur

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arokyne - October 30, 2023 at 1:34pm

Hi! This is a great tutorial but I am unable to get the 'Install macOS Big Sur' app. Here is why (I think). The Mac (M2 Mac mini) I'm using to access the App Store allows me to "Get" the app but then I get this error in System Preferences; Update not found: The requested version of macOS is not available. Please check if your Mac is compatible with this software. So I was able to download the 'InstallAssistant.pkg' for Big Sur but what do I do with this? How can I get the 'Install macOS Big Sur' app? Thank you!

iClarified - October 31, 2023 at 4:47pm

Are you aware that macOS Big Sur is not compatible with M2 Mac mini or are you intentionally trying to create a USB installer for a different device? You can install macOS Ventura or macOS Sonoma on the M2 Mac mini. https://www.iclarified.com/91547/how-to-create-a-bootable-macos-sonoma-usb-installer-video

arokyne - October 31, 2023 at 4:51pm

Sorry for the confusion. I’m just using the M2 Mac mini to download the OS. Then I’m installing it on my 2015 iMac

iClarified - November 1, 2023 at 4:23am

Download the InstallAssistant.pkg from here: https://www.iclarified.com/84324/where-to-download-macos-big-sur Then run the installer on your M2 Mac. It will place an app called "Install macOS Big Sur" in your Applications folder. You can then continue with the instructions as written in the tutorial.