Create bootable El Capitan ISO

create-bootable-el-capitan-iso.sh

#!/usr/bin/env bash -x

hdiutil attach "/Applications/Install OS X El Capitan.app/Contents/SharedSupport/InstallESD.dmg" -noverify -nobrowse -mountpoint /Volumes/install_app
exitStatus=$?
if [ $exitStatus -ne 0 ]; then
	exit $exitStatus
fi

# Convert the boot image to a sparse bundle
hdiutil convert /Volumes/install_app/BaseSystem.dmg -format UDSP -o "/tmp/El Capitan"
exitStatus=$?
if [ $exitStatus -ne 0 ]; then
	exit $exitStatus
fi

# Increase the sparse bundle capacity to accommodate the packages
hdiutil resize -size 8g "/tmp/El Capitan.sparseimage"
exitStatus=$?
if [ $exitStatus -ne 0 ]; then
	exit $exitStatus
fi

# Mount the sparse bundle for package addition
hdiutil attach "/tmp/El Capitan.sparseimage" -noverify -nobrowse -mountpoint /Volumes/install_build
exitStatus=$?
if [ $exitStatus -ne 0 ]; then
	exit $exitStatus
fi

# Remove Package link and replace with actual files
rm /Volumes/install_build/System/Installation/Packages
exitStatus=$?
if [ $exitStatus -ne 0 ]; then
	exit $exitStatus
fi

cp -rp /Volumes/install_app/Packages /Volumes/install_build/System/Installation/
exitStatus=$?
if [ $exitStatus -ne 0 ]; then
	exit $exitStatus
fi

# Unmount the installer image
hdiutil detach /Volumes/install_app
exitStatus=$?
if [ $exitStatus -ne 0 ]; then
	exit $exitStatus
fi

# Unmount the sparse bundle
hdiutil detach /Volumes/install_build
exitStatus=$?
if [ $exitStatus -ne 0 ]; then
	exit $exitStatus
fi

# Resize the partition in the sparse bundle to remove any free space
hdiutil resize -size `hdiutil resize -limits "/tmp/El Capitan.sparseimage" | tail -n 1 | awk '{ print $1 }'`b "/tmp/El Capitan.sparseimage"
exitStatus=$?
if [ $exitStatus -ne 0 ]; then
	exit $exitStatus
fi

# Convert the sparse bundle to ISO/CD master
hdiutil convert "/tmp/El Capitan.sparseimage" -format UDTO -o "/tmp/El Capitan"
exitStatus=$?
if [ $exitStatus -ne 0 ]; then
	exit $exitStatus
fi

# Remove the sparse bundle
rm "/tmp/El Capitan.sparseimage"
exitStatus=$?
if [ $exitStatus -ne 0 ]; then
	exit $exitStatus
fi

# Rename the ISO and move it to the desktop
mv /tmp/El\ Capitan.cdr ~/Desktop/El\ Capitan.iso
exitStatus=$?
if [ $exitStatus -ne 0 ]; then
	exit $exitStatus
fi

exit 0