I believe that is all generated via the buildinstall script from the 
anaconda-runtime rpm under /usr/lib/anaconda-runtime.

If memory serves it spits out usage information if you don't provide any 
args.

Pat

On 04/18/2017 02:48 PM, Mark Stodola wrote:
> Is there a resource/information/script on generating the initrd.img 
> used in the SL5 installation media?  I'm trying to inject kernel-lt 
> from ELrepo in place of the usual one.  Replacing vmlinuz is easy, but 
> I'm not sure where to start getting the initrd updated with the 
> appropriate kernel modules.
>
> I already know how to unpack the initrd, but I'm unsure how/where the 
> modules included in it are selected, gathered, and supporting files 
> created.
>
> -Mark