To install macOS Sierra 10.12, you must first download the official disk image from Apple, extract the installer app, and then either run it directly or create a bootable USB drive Apple Support 1. Download macOS Sierra 10.12

Open the mounted image and double-click the InstallOS.pkg file.

7. Security and Legal Considerations

If you absolutely need the DMG file for archival purposes, grab it directly from Apple using the terminal command above – it’s the only safe source.

  1. Open the App Store on a Mac running an older macOS.
  2. Go to the Purchased tab.
  3. Search for “macOS Sierra.”
  4. If associated with your Apple ID, click Download. This saves the installer as Install macOS Sierra.app (not a raw DMG).

Download the Package:

This will download a file named InstallMacOSX.dmg . Extract the Installer: Open the DMG file. Run the .pkg installer found inside.

Visit the official Apple Support Download Page for older macOS versions.

sudo /Applications/Install\ macOS\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume --applicationpath / Apple Support Community Create a bootable installer for macOS - Apple Support