Create macOS Catalina ISO File

# Create a Catalina Virtual Disk Image

hdiutil create -o /tmp/Catalina -size 8500m -volname Catalina -layout SPUD -fs HFS+J

# Mount this Image to macOS

hdiutil attach /tmp/Catalina.dmg -noverify -mountpoint /Volumes/Catalina

# Use macOS Createinstallmedia Tool to create a Installer Image

sudo /Applications/Install\ macOS\ Catalina.app/Contents/Resources/createinstallmedia --volume /Volumes/Catalina --nointeraction

# Unmount Volume Catalina

hdiutil detach /volumes/Install\ macOS\ Catalina

# Convert the Catalina.dmg to a Catalina.iso for Virtual Machine

hdiutil convert /tmp/Catalina.dmg -format UDTO -o ~/Desktop/Catalina.cdr

# Move and Rename Catalina Image to Desktop

mv ~/Desktop/Catalina.cdr ~/Desktop/Catalina.iso