How to Reinstall macOS Big Sur on an M1 Mac

By Connie | Posted to Home > Howto, updated on February 22nd, 2021 | User rating:

If you found that the current macOS performance of your M1 Mac is not well, you can try to reinstall macOS to get a new start. Or when you failed to solve issues like M1 Mac won't turn on or frequent system crashes, you can try to reset your M1 Mac or reinstall macOS Big Sur.

Reinstalling macOS needs to pay much caution because it will decide whether your M1 Mac gets into a new state or becomes a brick.

Follow the detailed ways in this article to reinstall macOS Big Sur on your M1 Mac.

Ways for reinstalling macOS Big Sur on M1 Mac

Reinstall macOS Big Sur in M1 Mac Recovery mode

If your M1 Mac can boot up but performs poorly when running macOS Big Sur, such as Mac runs slowly, try to solve it by reinstalling macOS.

First, you need to enter into macOS Recovery mode:

  • Restart your M1 Mac and continue to press and hold the power button.
  • Release the keys until you see the hint "Loading startup options".
  • Select Options and click Continue.
  • Type your admin password when asked.

Use the Reinstall macOS Big Sur utility in M1 Mac Recovery mode

Then, you can use the Reinstall macOS Big Sur utility to finish the macOS reinstallation on your M1 Mac.

With this approach, your personal data will remain on your PC after macOS reinstalling as long as you won't erase the data.

But for M1 Mac that won't boot due to internal hard drive inaccessible, unmountable, or other issues related to its file system, you need to erase your M1 Mac and then reinstalling macOS. The erasing procedure will make data loss. However, if you have a Time Machine backup, you can restore your M1 Mac with it.

How to avoid macOS reinstallation errors on M1 Mac

As the reinstallation process may occur some errors, macOS Big Sur won't resintall on M1 Mac. Hence, you should take care the following guidelines to enssure successful macOS reinstallation:

  1. Don't put your Mac to sleep or close its lid before the installation completing.
  2. When asked to unlock your disk, type your login password for your M1 Mac.
  3. Don't do any operation when you see that your Mac restart and show a progress bar several times or a blank screen for minutes. It's normal.
  4. If no disk shown up for the installer or a message says that the installer can't install on your disk, erase your disk first. (Erasing disk will make data loss)

Causes and solutions for macOS reinstallation failure

However, you still failed to reinstall macOS though you were careful enough. It might due to the bug of macOS Big Sur sometimes rather than your misoperations.

If you haven't updated to macOS 11.01 or later:

Your M1 Mac can't automatically switch to Internet Recovery mode though you've connected to the Internet when the recovery volume (contains a copy of macOS Big Sur) on the Internal disk is corrupted.

You can use other ways to reinstall macOS.

An error message may appear during macOS Big Sur reinstallation if you've erased your M1 Mac, like: "An error occurred preparing the update. Failed to personalize the software update. Please try again."

An error occurred preparing the update

You can use the Apple Configurator 2 on the other Mac to revive or restore your M1 Mac

Reinstall macOS on M1 Mac in Internet Recovery mode

For macOS Big Sur 11.01 & later, Internet Recovery mode is fully supported without bugs on M1 Mac. Once the macOS installer can't be reinstalled from the local recovery volume (Because it is corrupted) in Mac Recovery mode, it will automatically switch to Internet Recovery mode if you've connected to the Internet. Then, you can download a macOS installer from the Internet and reinstall macOS.

Note: If you connected to a shared network like a hotel network, you might be unable to access the internet in macOS Recovery mode.

Other ways to reinstall macOS on M1 Mac

If the above ways are not working for some reason, you can try other ways as replacements.

Use Terminal in Mac Recovery mode to reinstall macOS

If you fail to reinstall macOS neither with the Reinstall macOS feature in macOS Recovery mode nor from the Internet, using Terminal is an alternative.

Before using Terminal to reinstall macOS, you need to back up or recover your data.

Note: Connect to Internet in Mac Recovery mode.

  • Type the following command in Terminal window and pressReturn.
  • resetpassword
  • Click the Reset Password window. Then choose Recovery Assistant > Erase Mac.
  • Click Erase Mac again to make a confirmation. Then, your M1 Mac will restart automatically.
  • Select your language when required.
  • Click macOS Utilities when you see a message about "Your version of macOS must be reinstalled" to activate your M1 Mac.
  • Click Exit to Recovery Utilities after your Mac is activiated.
  • Select Utilities > Terminal again.
  • Type the commands as below and then press Return to download macOS Big Sur.
  • cd '/Volumes/Untitled'
    mkdir -p private/tmp
    cp -R '/Install macOS Big' private/tmp
    cd 'private/tmp/Install macOS Big'
    mkdir Contents/SharedSupport
    curl -L -o Contents/SharedSupport/SharedSupport.dmg ~
  • Enter the following command in Terminal when the macOS downloading process is done. Then, press Return.
  • ./Contents/MacOS/InstallAssistant_springboard
  • Follow the instructions to reinstall macOS when the macOS installer opens.

Create and use a bootable installer to reinstall macOS

If macOS Recovery mode doesn't work, creating a bootable installer by yourself. To create a bootable installer, you need to download macOS installation files on an external storage device formatted with Mac OS Extended via a healthy Mac. Then, install macOS from the created bootable installer.

Reinstalling macOS on an M1 Mac is something that looks simple but operates hard. Because the situation which you are in decides the macOS reinstalling way you'll choose. This article offers a complete guide to cater for almost all situations you may run into and help you reinstall macOS on M1 Mac successfully.

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