sudo /Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/USB

: For users already on 10.13.5 (1.9 GB).

If your installer is an older version of High Sierra, you can jump straight to the final build by downloading the directly from Apple’s website. This ensures all security patches are up to date.

Connect a flash drive (at least 16GB) and rename it to MyVolume .