[Guide] How to Create macOS Big Sur Bootable USB


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Jul 22, 2018
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The following guide is a guide for creating macOS Big Sur Bootable USB. The installation has been covered in another section.

Before you start with this guide, here's are few requirements
  • A working Internet connection.
  • A 16 GB or larger USB Flash Drive.
  • A complete backup of your system. We advise you to perform a complete backup of your system along with the existing installation. In case something goes wrong, you can restore it using the backup you created.
To start with the guide, you'll also need to have access to fully functional computer running macOS Mojave or later. This requirement is must as you need to access to Mac App Store in order to download a copy of macOS and create a installation USB Flash Drive later on.

Download macOS Big Sur
The very first step is to download macOS Big Sur. The copy of macOS is available for free to download for anyone who has purchased a Mac with macOS High Sierra or greater. Currently Apple has announced their new release of macOS which is only available to Developers for beta testing. Download the copy of macOS from Apple Developer's program using your Apple ID on any Mac.

Here are the steps to download the copy of macOS Big Sur
  1. Login into Developer Program with your Apple ID.
  2. Under macOS, find macOS Big Sur and download the Beta Access Utility.
Once the download is complete, mount the .DMG file and install the package. After installing, the System update will appear and it will display the new macOS Big Sur update. Click on Upgrade and it will start downloading the copy of new macOS. Once the download is complete, it will appear in your Applications folder named as Install macOS Beta.

Creating a Bootable USB Flash Drive with Createinstallmedia
The next step is to create a bootable installation drive. Follow the steps below to create the installation media.

1. Insert your USB Flash Drive and open Disk Utility. The Disk Utility is located at /Applications/Utilities/Disk Utility
2. Select your USB Flash Drive in the left pane and click on Erase button, at top.
3. A pop-up will appear.
4. Under Name type USB

5. Under Format select Mac OS X Extended (Journaled)

6. Under Scheme select GUID Partition Map, and click on Erase.

7. When done, click on Done.

8. Launch terminal, located at /Applications/Utilities/Terminal.

9. Copy and paste the following sudo command in terminal.

sudo /Applications/Install\ macOS\ Beta.app/Contents/Resources/createinstallmedia --volume /Volumes/USB
10. Enter your password

11. Press (Y) to confirm and then press enter key and it will start to erase the disk and will create macOS Bootable USB.

Once the process completes, close the terminal. The USB Flash Drive will be renamed as Install macOS Beta

12. Once the process gets completed, restart your Mac and while restarting, hold down the option key and select your USB Flash Drive and boot from it. The installer will load in a while.