Use tools likeRufus/balenaEtcher (forWindows) orEtcher(forLinux) to create a bootable USB drive from your custom ISO. balenaEtcher Interface If you want to share your custom ISO, consider uploading it to a file-sharing service or hosting it on a personal website. If you followed all the ...
Click onChoose Startup Diskand then pick any bootable drive you've got attached. The Mac will restart and it will boot from that drive. It will now boot from any drive you connect over USB or Thunderbolt so you can keep an emergency clone ready to go at any time. Now you've don...