I did the dd if=CentOS-8.1.1911-x86_64-dvd1.iso of=/dev/sdd to a 16G USB disk then tried to use it on an install. The installer said invalid install media. Any way to verify if the "write" to disk was good ? I got no errors on the dd. I did re-download the iso and did a diff and there was no diff. So I think my iso is OK. Jerry