# Navigate to your desktop for easy access cd ~/Desktop hdiutil create -o ElCapitan.cdr -size 7320m -layout SPUD -fs HFS+J -type SPARSE Mount the blank image hdiutil attach ElCapitan.cdr.sparseimage -noverify -mountpoint /Volumes/install_build Step 2: Restore the Installer to the Blank Image # This copies the bootable installer contents (requires sudo) sudo asr restore -source /Applications/Install\ macOS\ El\ Capitan.app/Contents/SharedSupport/InstallESD.dmg -target /Volumes/install_build -erase -noverify -puppetstrings Note: The -puppetstrings flag is essential; it bypasses permission mismatches that cause "Invalid argument" errors on modern macOS versions. Step 3: Detach and Convert to ISO # Detach the built volume hdiutil detach /Volumes/OS\ X\ Base\ System Convert the sparse image to a standard ISO (CDR format) hdiutil convert ElCapitan.cdr.sparseimage -format UDTO -o ElCapitan.iso Rename the .cdr file to .iso (they are identical formats) mv ElCapitan.iso.cdr ElCapitan_HS.iso
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