mv HighSierra_10.13.5.iso.cdr HighSierra_10.13.5.iso To ensure your ISO is not corrupted, compare the MD5 or SHA-1 hash with known community-sourced values for the legitimate 10.13.5 build.
hdiutil convert /path/to/InstallESD.dmg -format UDTO -o /path/to/HighSierra_10.13.5.iso This creates a .cdr file. On macOS, .cdr is functionally identical to .iso . Simply rename the extension: macos high sierra 10.13.5.iso
If you need this specific build for iCloud Messages sync testing or legacy audio drivers, follow the Terminal method above. Convert the official InstallESD.dmg to an ISO. It takes 10 minutes and guarantees a clean, bootable, and legal copy. mv HighSierra_10