Use Apple's built-in tool to write the installer files into the mounted disk image:
The official and safe method is to obtain the full Install macOS Catalina.app installer directly from Apple. This installer bundle, which can be thought of as the functional equivalent of a DMG, contains all the necessary files for a clean installation.
If you are currently running a compatible version of macOS, downloading directly from Apple ensures total file integrity:
: If the App Store doesn't work, you can force the download using this command: Use Apple's built-in tool to write the installer
or Software Update will open. Click Download .
This step will erase everything on your computer. 1. Boot into Recovery Mode
Open and identify the exact name of your USB drive. Click Download
To perform a clean installation, you need a USB flash drive (at least 16GB) to turn into a bootable installer. Download the Installer: Ensure the "Install macOS Catalina" app is in your /Applications Format the USB: Disk Utility , select your USB drive, and format it as Mac OS Extended (Journaled) with a GUID Partition Map. Name it "Catalina". Create Installer:
Once you have the Install macOS Catalina.app file in your /Applications folder, you can create your bootable USB installer. The most reliable method is using the built-in createinstallmedia command in .
Your Mac will now begin copying files and setting up the system. This process can take anywhere from 15 to 45 minutes depending on your hardware speed. Your Mac will restart automatically during this process—leave the USB drive plugged in until you are greeted by the welcome setup assistant screen. Boot into Recovery Mode Open and identify the
To reinstall macOS on a wiped drive, you must write the installation media onto an external USB flash drive.
Type your admin password, press Enter, and press Y to confirm that you want to erase the drive.