macOS Sierra is no longer receiving security updates. It is considered "End of Life" by security standards. Using it for banking or accessing sensitive data is highly discouraged.
createinstallmedia tool to copy the installer files. Create a blank disk image: hdiutil create -o /tmp/Sierra -size 8G -layout SPUD -fs HFS+J Mount the image: hdiutil attach /tmp/Sierra.dmg -noverify -mountpoint /Volumes/SierraISO Copy the installer files: sudo /Applications/Install\ macOS\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/SierraISO --applicationpath /Applications/Install\ macOS\ Sierra.app --nointeraction Unmount the image: hdiutil detach /Volumes/SierraISO Convert DMG to ISO: hdiutil convert /tmp/Sierra.dmg -format UDTO -o ~/Desktop/Sierra.cdr Rename to .iso: mv ~/Desktop/Sierra.cdr ~/Desktop/Sierra.iso Alternative: Using Third-Party Tools If you prefer a graphical interface or are working on Windows, you can use specialized software: Mist (macOS): An open-source tool that automates the downloading and creation of bootable macOS installers and ISOs. createinstalliso (GitHub): A community-made script available on GitHub specifically designed to create bootable ISO images from macOS installer apps. DMG Editor (Windows): Tools like DMG Editor can help burn macOS disk images to USB or convert formats on a PC. Would you like the mac os sierra iso