How to create a macOS Big Sur bootable disk and use it to install it from scratch

Although Big Sur is currently in beta, it may create a bootable external drive with which to perform a clean system install Is very helpful. This way we can completely remove the old installation and create a new one which, in theory at least, should have better performance and less downtime.

What we need to create a bootable USB drive with macOS Big Sur

For this process we will need a flash memory with at least 16 GB of storage. Keep in mind that we will completely erase your content, so if necessary, we will save the files to another location.

We will also need a copy of the Big Sur configuration app. We can get this app through the developer portal or through the public beta.

Last but not the least, the Mac with which we create the installer, even if it is intended for another Mac, must be compatible with Big Sur.

Terminal, on and goes

Okay, gathered the necessary ingredients Let’s get to work. The process is quite simple and consists of these steps:

  • We connect the flash memory to the Mac and change the name to “FLASH”, without the quotes.
  • We open the app Terminal, which we can search using Spotlight.
  • We copy and paste the appropriate command based on the beta we downloaded.
  • For macOS Big Sur in public beta:

    sudo / Applications / Install macOS Big Sur –volume / Volumes / FLASH –nointeraction

    For macOS Big Sur in developer beta:

    sudo / Applications / Install macOS 11 –volume / Volumes / FLASH –nointeraction

  • We press Enter (↩︎).
  • We write down our Mac’s password and press Enter again.
  • The process can take up to 20 minutes depending on the speed of the computer we are using. We will see multiple process flags in the same terminal and when done we will see “Done” in the last line. And just like that, we created a Big Sur bootable installer.

    And now what?

    We can now proceed with the installation of Big Sur from scratch. To do this, we simply turn off the computer, we connect the flash memory and turn it on by pressing the option key (⌥). When the menu to choose appears, we select the Big Sur installer.

    Remember that some Macs with T2 chip need us to enable this external boot option. To do this, we simply shut down the Mac and turn it on by pressing Command (⌘) + R. Then in the menu Utilities we choose Boot Security Utility and we will mark the option * Allow booting from external media. After restarting the computer, we will be able to use our installer on Mac.

    Keep in mind that for the installation to be from scratch, it is necessary to erase the contents of the entire hard drive, the process is very simple, as our colleague Miguel López explains in the following video:

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    And this simple. We’ve created a bootable macOS Big Sur installer and seen how to use it to create a clean system install. A resource that requires us to reinstall apps and settings after the process, but can improve errors and overall computer performance.