Back up any existing data on the USB drive, as this process erases it entirely. Step-by-Step Terminal Guide Plug your USB flash drive into your Mac. Open (Finder > Applications > Utilities). Select your USB drive and click Erase .
As of 2026, Apple maintains legacy support pages. The safest way to download macOS Sierra is directly from the Apple Support servers. mac os sierra 1012dmg download free
The screen filled with hundreds of thumbnails. Vivid, beautiful, high-resolution color photographs of a city long gone, captured through his grandfather's artistic eye. Leo leaned back in his chair, the glow of the old screen illuminating his face, realizing that a simple, free download had just rescued a lifetime of memories. Back up any existing data on the USB
Double-click the .pkg and follow the prompts. This does not install the OS yet; it places the "Install macOS Sierra" app into your Applications folder. Select your USB drive and click Erase