usb boot - USB thumb drive with CentOS 7 not booting

I am trying to create a custom bootable CentOS 7 ISO that boots from USB.

1. I have downloaded the CentOS minimal DVD



2. I have used dd to put the ISO onto the thumbdrive:

   
   

   dd if=CentOS-7-x86_64-Minimal-1511.iso of=/dev/sdb bs=4MB
   




3. I have tried multiple options to boot from DVD like changing boot order and disabling/enabling UEFI bios but it just does not boot from the thumb drive. The ISO works fine if I burn it to DVD.

What can I do to get it to boot?

Answer

When generating a custom centos ISO, to get it to boot in a usb stick, isohybrid required.

In my case I was using isohybrid but I the variable I was using as the iso path was wrong. As a result isohybrid was failing