Open Terminal and enter the following command: sudo /Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume
Press Enter and authenticate. The system will download the 5.2GB installer directly from Apple’s content delivery network. Once complete, you will find Install macOS High Sierra.app in your Applications folder. Mac Os High Sierra Download Dmg
Double-click your downloaded DMG file to mount it. Open Terminal and enter the following command: sudo