sudo /Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/HighSierra --nointeraction Use code with caution. Detach the newly created volume: hdiutil detach /Volumes/Install\ macOS\ High\ Sierra Use code with caution.

Step 1: Download macOS High Sierra 10.13.6 DMG Full Installer

: If you only get a small "stub" installer (~20MB), you may need to use a terminal command or a script to fetch the full 5GB version. 2. Terminal Method (For macOS Catalina or later)

Apple delivers the OS as an .app bundle ( Install macOS High Sierra.app ). If your final use case requires a standard .dmg image file, you can build one manually via the Terminal. Open Terminal and execute these commands sequentially: Create a blank disk image wrapper:

Terminal will download the full installer application directly into your folder. Method 3: Third-Party Sources (Proceed with Caution)

Open your web browser and visit the official Apple Support documentation for older macOS versions. Click the link for . Your browser will prompt to open the Mac App Store .

For Macs with traditional hard disk drives (HDD) or Fusion Drives, APFS is not enabled by default; these systems continued using HFS+ after the upgrade.

Open and erase the drive. Name it Untitled and format it as Mac OS Extended (Journaled) with a GUID Partition Map . Close Disk Utility and open Terminal .

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When downloading DMG files from any third-party site, always verify the file's checksum (e.g., SHA256) against a known good value to ensure the file has not been tampered with.