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.
#===========================================================================

DISK_SIZE="${2:-16016m}"
VERSION="${1:-Sequoia}"

#===========================================================================

echo "Using '$VERSION' for macOS version, and size of '$DISK_SIZE'."
hdiutil create -o "/tmp/$VERSION.cdr" -size $DISK_SIZE -layout SPUD -fs HFS+J
hdiutil attach "/tmp/$VERSION.cdr.dmg" -noverify -mountpoint /Volumes/install_build
extra_size=`sudo /Applications/Install\ macOS\ $VERSION.app/Contents/Resources/createinstallmedia  --volume /Volumes/install_build --nointeraction 2>&1`
if [[ ! "$extra_size" == *"additional"* ]]; then
    hdiutil detach "/Volumes/Install macOS $VERSION"
    hdiutil convert "/tmp/$VERSION.cdr.dmg" -format UDTO -o "/tmp/$VERSION.iso"
    mv "/tmp/$VERSION.iso.cdr" ~/Desktop/$VERSION.iso
    rm "/tmp/$VERSION.cdr.dmg"
else
    extra_size="$(echo $extra_size | awk '{ print $11 }')"
    extra_size=`expr $extra_size*1024+1 | bc`
    extra_size=${extra_size%.*}
    DISK_SIZE=${DISK_SIZE::${#DISK_SIZE}-1}
    DISK_SIZE=`expr $DISK_SIZE+$extra_size | bc`
    DISK_SIZE="${DISK_SIZE}m"
    echo "New Size: $DISK_SIZE"
    rm "/tmp/$VERSION.cdr.dmg"
    hdiutil create -o "/tmp/$VERSION.cdr" -size $DISK_SIZE -layout SPUD -fs HFS+J
    hdiutil attach "/tmp/$VERSION.cdr.dmg" -noverify -mountpoint /Volumes/install_build
    sudo /Applications/Install\ macOS\ $VERSION.app/Contents/Resources/createinstallmedia  --volume /Volumes/install_build --nointeraction 2>&1
    hdiutil detach "/Volumes/Install macOS $VERSION"
    hdiutil convert "/tmp/$VERSION.cdr.dmg" -format UDTO -o "/tmp/$VERSION.iso"
    mv "/tmp/$VERSION.iso.cdr" ~/Desktop/$VERSION.iso
    rm "/tmp/$VERSION.cdr.dmg"
fi