[GUIDE] Clean Install macOS without a USB Drive

Discussion in 'macOS' started by cbsvitzer, May 1, 2021.

  1. cbsvitzer

    cbsvitzer MDL Member

    Feb 4, 2010
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    #1 cbsvitzer, May 1, 2021
    Last edited: May 3, 2021
    Clean install macOS without a USB Drive

    Since Catalina it has been possible to reinstall macOS without having to boot to a USB drive or creating a new partition with the installer. It is just a matter of some simple Terminal commands.

    Be sure to make a Time Machine backup first because everything will be deleted!!!

    First we download the installer app, then we start a new installation.

    Open Terminal and type the following command:

    Download latest installer:
    sudo softwareupdate --fetch-full-installer

    When the installer is downloaded you proceed with the following command, depending on which installer was downloaded:

    Install Big Sur:
    /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/startosinstall --eraseinstall --agreetolicense --forcequitapps --newvolumename 'Macintosh HD'

    Install Catalina:
    /Applications/Install macOS Catalina.app/Contents/Resources/startosinstall --eraseinstall --agreetolicense --forcequitapps --newvolumename 'Macintosh HD'
     
  2. colinzim

    colinzim MDL Senior Member

    May 14, 2007
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    Thanks, is fast method.

    and here using gui, disk utilty

    https://forums.mydigitallife.net/threads/install-macos-no-usb-dvd-boot.74580/