🛠️ Step 2: Create a macOS Catalina ISO Image via Terminal
You cannot download a finished ISO from Apple, but you can download the official .app installer for free.
: Official disk images for some older macOS versions (though primarily those pre-dating Catalina) can be found on Apple Support How to download and install macOS - Apple Support Macos Catalina Iso Image - Download
The installer will appear in your folder once the progress bar hits 100%.
Once you have the Install macOS Catalina.app sitting in your Applications folder, you can safely build your own bootable ISO file by running the following sequence of commands in your Terminal: 🛠️ Step 2: Create a macOS Catalina ISO
Apple only distributes the macOS Catalina installer through the Mac App Store or via Terminal as an application or DMG file.
Run the following command to pull the official full installer: Run the following command to pull the official
hdiutil create -o /tmp/Catalina -size 8500m -volname Catalina -layout SPUD -fs HFS+J
You do not need an ISO for this—use the .app directly. But if you only have the ISO:
Next, we mount this blank image so we can write data to it.