Creating a macOS Catalina 10.15.7 ISO requires a two-part process: downloading the official installer from Apple and using the Terminal to convert it into a bootable disk image. 1. Download the Catalina Installer
: hdiutil create -o /tmp/Catalina -size 8500m -volname Catalina -layout SPUD -fs HFS+J macos catalina 10157 iso download new
: hdiutil attach /tmp/Catalina.dmg -noverify -mountpoint /Volumes/Catalina Creating a macOS Catalina 10
Mount that DMG:
: You can trigger a download of the full installer directly from Apple's servers by running this command in your Terminal: softwareupdate --fetch-full-installer --full-installer-version 10.15.7 macos catalina 10157 iso download new