How to Create macOS Big Sur Bootable USB Install Drive

Saturday, November 14, 2020 6:10 AM

How to Create macOS Big Sur Bootable USB Install Drive

How to make a macOS Big Sur beta boot installer drive

Advanced Mac users often want to make a boot disk installer for macOS Big Sur beta, allowing for something like a USB flash drive to be used to boot and install macOS Big Sur onto any compatible Mac.

Bootable MacOS installer USB drives provide for the ability to clean install macOS Big Sur, update to macOS Big Sur, install macOS Big Sur beta onto multiple Macs without redownloading the installer, as well as the ability to use Disk Utility to partition and erase a machine, perform Time Machine restorations, and more.

If you’re interested in creating a macOS Big Sur bootable USB install drive, this tutorial will walk through that process.

Requirements for making a boot macOS Big Sur USB Install Drive

To make a bootable macOS Big Sur installer drive, you will need the following:

If you haven’t already downloaded the macOS Big Sur installer application, you will need to do that before beginning the process, meaning you will also need an internet connection.

The rest of the process of creating a macOS Big Sur (macOS 11  USB installer drive involves the terminal. This means that this process is most appropriate for advanced users with understanding of the command line. Improper usage of the command line in this process may result in permanent data loss by erasing the wrong disk. If you’re not thoroughly certain of your capabilities, backup your Mac before beginning.

How to Make a Bootable macOS Big Sur USB Installer Drive

Be sure to use precise syntax at the command line, failure to do so may result in permanent data loss. Proceed at your own risk.

  1. Connect the USB flash drive to the Mac that you wish to turn into the bootable macOS Big Sur installer, naming the drive “UNTITLED” * 
  2. Open the “Terminal” application via Spotlight by hitting Command + Spacebar and typing Terminal and hitting the return key, through Launchpad, or via the Utilities folder in the Finder
  3. Enter the command at the Terminal command line corresponding to the version of macOS Big Sur you have (versions have different application installer names), assuming “UNTITLED” is the name of the USB flash drive to convert into a bootable macOS Big Sur install drive:
  4. 4.MacOS Big Sur final
    sudo /Applications/Install macOS Big --volume /Volumes/UNTITLED --nointeraction

  5. Double-check that the syntax is correct and the volume is specified properly, then hit the return / enter key and enter the admin password to start the boot installer creation process **

Let the process complete, it can take a while depending on the speed of the Mac, the speed of the USB flash drive being used, and other variables. When completed, the terminal will report a “Done” message.

Once the macOS Big Sur 11.0 USB bootable installer drive has been created successfully, it will be mounted automatically on the Mac and ready to use. 

At this point you can use the macOS Big Sur bootable install drive just like any other boot disk or installation drive on any other macOS Big Sur compatible Mac.

* You can name the USB flash drive something else, but the syntax as written is intended or a drive named UNTITLED (which is the default for a recently formatted drive through Disk Utility).

** If a “command not found” error message appears at the command line, it’s likely due to a syntax error, or because the “Install” is not found in the Applications folder as expected. Double-check the syntax for typos and make sure the macOS Big Sur installer is found in the /Applications directory.

How to Boot a Mac with the macOS Big Sur USB Install Drive

Booting a Mac with a boot disk is pretty straight forward in most cases ***:

  1. Connect the macOS Big Sur install drive to the Mac
  2. Restart the Mac if it’s already started up, otherwise boot it up as usual
  3. Immediately hold down the OPTION key upon Mac boot, continuing to hold OPTION / ALT until you see the Mac boot menu
  4. Select the macOS Big Sur installer volume to start the Mac from

What if the Mac won’t boot from the macOS Big Sur USB bootable install drive?

*** Note that on some newer Macs with the security chip you may need to manually enable the ability to start the Mac from an external boot disk. Do this by:

  1. Reboot the Mac holding down Command + R to go into Recovery Mode
  2. Select “Startup Security Utility” from the Utilities menu and authenticate with admin
  3. Choose to “Allow booting from external media”

This will allow the Mac to boot from the Big Sur boot install disk as usual with the directions above.

Regardless, once the Mac is booted from the macOS Big Sur installer drive, you can format the Mac, partition it, modify and create APFS volumes, restore from Time Machine, clean install, upgrade Macs to MacOS Big Sur, and much more.