Then, follow Apple's official documentation to properly create a bootable installer.
A full High Sierra installer should be roughly 5.2GB . download macos high sierra 10.13.6 dmg mac
hdiutil create -o /tmp/HighSierra -srcfolder "/Applications/Install macOS High Sierra.app" -format UDZO download macos high sierra 10.13.6 dmg mac
This guide provides everything you need to know. We will cover why this specific build (10.13.6) is critical, where to find a legitimate DMG file, how to create a bootable USB installer, and how to troubleshoot common installation issues. download macos high sierra 10.13.6 dmg mac