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Downloading and installing macOS Big Sur via macOS Recovery’s Terminal

Every so often, you may find yourself in a situation where you need to reinstall macOS Big Sur and everything is failing on you. Installing from macOS Recovery? Not working via the usual methods. Building a USB installer? Left the flash drive in your other pants. Using DFU mode and Apple Configurator on an Apple Silicon Mac? You need a second Mac to use this process and you just have the one Mac available.

For those situations, there’s one more option when you’ve exhausted all of the others. For more details, please see below the jump.

This method is referenced in the following Apple KBase article:

https://support.apple.com/HT211983

It involves the following:

  • Wiping the drive that you intend to install macOS Big Sur onto.
  • Creating the proper directory structure manually on the drive.
  • Copying the Install macOS app available in macOS Recovery manually into the proper location on the drive 
  • Using the curl tool to download the needed installer files onto the drive
  • Launching the Install macOS app
  • Using the Install macOS app to install macOS Big Sur

To install macOS Big Sur using the methods described above, use the procedure below:

1. Boot to macOS Recovery.

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2. Erase your Mac’s startup drive using the correct procedure for your Mac model:

Macs with Intel processors: https://support.apple.com/HT208496
Apple Silicon Macs: https://support.apple.com/kb/HT212030

By default, an erased drive is named Untitled. We’ll be using that drive name for the examples shown in this post.

2. Once the drive is erased, open Safari and go to the following URL:

https://support.apple.com/HT211983

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3. Scroll to the bottom of the KBase article and locate the Or use Terminal to reinstall section.

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4. Copy the complete command which begins with curl. (This will save a lot of typing later.)

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5. Quit Safari.

6. Open Terminal.

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7. Run the following command to change to using the drive named Untitled:

cd "/Volumes/Untitled"

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8. Run the following command to create a directory named private on the Untitled drive as well as a sub-directory inside of private which is named tmp:

mkdir -p private/tmp

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9. Run the following command to copy the Install macOS Big Sur.app application from macOS Recovery to the /Volumes/Untitled/private/tmp directory.

cp -R "/Install macOS Big Sur.app" private/tmp

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10. Run the following command to change to the /Volumes/Untitled/private/tmp/Install macOS Big Sur.app directory:

cd "private/tmp/Install macOS Big Sur.app"

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11. Run the following command to create a directory named Contents on the Untitled drive as well as a sub-directory inside of Contents which is named SharedSupport:

mkdir Contents/SharedSupport

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12. Paste the copied curl command and hit the enter key on your keyboard to have the macOS Big Sur installer files be downloaded into a file named SharedSupport.dmg. The SharedSupport.dmg will be located in /Volumes/Untitled/private/tmp/Install macOS Big Sur.app directory/Contents/SharedSupport.

curl -L -o Contents/SharedSupport/SharedSupport.dmg https://swcdn.apple.com/content/downloads/01/60/071-72781-A_CZ1D1FENMH/a09fvud3xxgih7qyau9a7lhtspho36mp0l/InstallAssistant.pkg

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13. Once curl has finished downloading /Volumes/Untitled/private/tmp/Install macOS Big Sur.app directory/Contents/SharedSupport/SharedSupport.dmg, run the following command to launch the macOS Big Sur installer.

./Contents/MacOS/InstallAssistant_springboard

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14. Follow the prompts to install macOS Big Sur.

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  1. Peteo
    August 4, 2021 at 5:18 pm

    Great post!

  2. Graham
    August 5, 2021 at 10:38 am

    I’m guessing this command won’t work:

    mkdir Contents/SharedSupport

    But this will:

    mkdir -p Contents/SharedSupport

    • August 5, 2021 at 1:47 pm

      If the Contents directory didn’t already exist, that would be correct and “mkdir -p” would be needed. In this case, the Contents directory already existed inside of the copied Install macOS Big Sur.app.

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