Simple bash script to create a Bootable ISO from macOS Catalina Install Image from Mac App Store

create-iso.sh

#!/usr/bin/env bash
#===========================================================================
# Works only with the official image available in the Mac App Store.
# Make sure you download the official installer before running this script.
#===========================================================================

echo "1/7: create Catalina.cdr"
hdiutil create -o Catalina.cdr -size 9000m -layout SPUD -fs HFS+J
echo "2/7: mount"
hdiutil attach Catalina.cdr.dmg -noverify -mountpoint /Volumes/install_build
echo "3/7: create install media"
sudo ./Install\ macOS\ Catalina.app/Contents/Resources/createinstallmedia  --volume /Volumes/install_build --nointeraction
echo "4/7: detach"
hdiutil detach "/Volumes/Install macOS Catalina"
echo "5/7: convert"
hdiutil convert Catalina.cdr.dmg -format UDTO -o Catalina.iso
echo "6/7: rename to iso"
mv Catalina.iso.cdr Catalina.iso
echo "7/7: remove temp img"
rm Catalina.cdr.dmg