> On May 24, 2018, at 2:17 PM, Bill <[log in to unmask]> wrote:
> 
> I am creating a custom installation ISO using kickstart.  This install ISO is based on SL 7.2.
> 
> When I burn a DVD from this ISO I can boot from the DVD and the install menu come up as expected.  
> 
> When I use dd to copy the ISO to a USB key and try to boot from the USB key the install menu does not appear and the system boots from the hard drive.  
> 
> I tried using dd to copy the SL7.2 ISO to a USB key.  When I try to boot from this USB key the install menu comes up as expected.
> 
> What files on the SL7.2 have to do with booting from the USB key?

“Any if them”, especially the boot loader, which is normally written *before* the partition information and superblicks for the filesystem. That was what “dd” copies first which file copies would not copy.

> 
> Is there a mkisofs option I should be using to make booting USB key work?

“dd” is your friend. There are many guidelines for building bootable cd’s you could review, but you can probably save a lot of work not using that.