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Preparing for OpenCore Upgrade

A fresh install of macOS isn't required for OpenCore, though some users prefer starting anew.

Obtaining macOS

If you're not creating a full installer but only a bootable OpenCore USB, you can skip macOS download. Otherwise:

1. Direct Download: Get macOS from the App Store.

2. Munki's Utility: For specific releases or without App Store access, use the following Terminal commands:

   bashCopy code
   mkdir ~/macOS-installer && cd ~/macOS-installer
   curl -O https://raw.githubusercontent.com/munki/macadmin-scripts/main/installinstallmacos.py
   sudo python installinstallmacos.py
   

Downloading macOS: Modern OS

For macOS 10.13 and newer, download from the App Store. For older versions, see Downloading macOS: Legacy OS.

Note for macOS 11, Big Sur: Check the latest updates and issues at OpenCore and macOS 11: Big Sur.

Nvidia GPU Users: Ensure compatibility with newer macOS versions at Hardware Limitations.

After downloading, the installer (e.g., Install_macOS_11.1-20C69.dmg) will be in ~/macOS-Installer/. Mount it to access the Installer application.

Continue reading the guide while the download completes, then proceed to Setting up the installer.

Setting up the Installer

1. Format a USB drive with macOS Extended (HFS+) and a GUID partition map. This creates MyVolume and EFI partitions.

2. Use the createinstallmedia command to create bootable media:

   bashCopy code
   sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume
   

3. Mount the EFI partition and add OpenCore's files.

4. Follow Set up the EFI for final steps.

This streamlined guide offers a straightforward approach to preparing for OpenCore installation, including macOS download and USB preparation.