hdiutil create -o /tmp/Catalina -size 8500m -volname Catalina -layout SPUD -fs HFS+J This makes an 8.5 GB empty hard disk image.

sudo /Applications/Install\ macOS\ Catalina.app/Contents/Resources/createinstallmedia --volume /Volumes/Catalina --nointeraction This takes 10-15 minutes. This is the critical step where Apple’s tool builds the bootable recovery system inside your DMG.

hdiutil detach /Volumes/Install\ macOS\ Catalina

If you found this guide helpful, you might also search for "how to install Catalina on unsupported Mac" or "VirtualBox guest additions for macOS Catalina" . Need help? Leave a comment below (if on a blog) or consult the r/macOS subreddit. Safe computing!

diskutil eraseVolume JHFS+ Catalina /Volumes/Catalina