A USB flash drive of at least 8GB . (Back up data on the drive first, as this process erases it).
softwareupdate --fetch-full-installer --full-installer-version 10.12 10.12 sierra download
Note: This works on macOS High Sierra or newer. If the command fails, use the manual URL method. A USB flash drive of at least 8GB
(Look for the Sierra 10.12 link under "Use a web browser") 10.12 sierra download
sudo /Applications/Install\ macOS\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume --applicationpath /Applications/Install\ macOS\ Sierra.app
Ensure you are using the hidden link provided in Phase 1. Searching manually in the App Store search bar rarely works for OS versions older than Mojave.
: You must be running at least OS X Lion 10.7.5 to upgrade directly. 🛠️ How to Install macOS Sierra - Technical Specifications - Apple Support