# Mount the installer image
hdiutil attach /Applications/Install\ OS\ X\ Yosemite.app/Contents/SharedSupport/InstallESD.dmg -noverify -nobrowse -mountpoint /Volumes/install_app
# Convert the boot image to a sparse bundle
hdiutil convert /Volumes/install_app/BaseSystem.dmg -format UDSP -o /tmp/Yosemite
# Increase the sparse bundle capacity to accommodate the packages
hdiutil resize -size 8g /tmp/Yosemite.sparseimage
# Mount the sparse bundle for package addition
hdiutil attach /tmp/Yosemite.sparseimage -noverify -nobrowse -mountpoint /Volumes/install_build
# Remove Package link and replace with actual files
rm /Volumes/install_build/System/Installation/Packages
cp -rp /Volumes/install_app/Packages /Volumes/install_build/System/Installation/
# Copy BaseSystem.dmg and Basesystem.chunklist
cp /Volumes/install_app/BaseSystem.dmg /Volumes/install_build/
cp /Volumes/install_app/Basesystem.chunklist /Volumes/install_build/
# Unmount the installer image
hdiutil detach /Volumes/install_app
# Unmount the sparse bundle
hdiutil detach /Volumes/install_build
# Resize the partition in the sparse bundle to remove any free space
hdiutil resize -size `hdiutil resize -limits /tmp/Yosemite.sparseimage | tail -n 1 | awk '{ print $1 }'`b /tmp/Yosemite.sparseimage
# Convert the sparse bundle to ISO/CD master
hdiutil convert /tmp/Yosemite.sparseimage -format UDTO -o /tmp/Yosemite
# Remove the sparse bundle
rm /tmp/Yosemite.sparseimage
# Rename the ISO and move it to the desktop
mv /tmp/Yosemite.cdr ~/Desktop/Yosemite.iso