CentOS

I'm trying to install from the CentOS 6.9 DVD install, I want to specify a kickstart file to use but I can't seem to pull up the usual boot prompt. I tried escape at the menu below, nothing happens. Pressing c for cmd line gives me the grub prompt instead.

Well, there aren't that many choices that you could try.. How about e?

Tried that, e only allows you to edit the kernel and initrd lines of the 3 options shown in the menu.

UPDATE: So I tried the DVD on an older server as a sanity check and I get the screen below which I don't get on the other newer server, this is the normal screen I've seen before with previous CentOS 6.x installers, pressing escape here gives me the boot prompt. So this issue here is related to the new server, it's UEFI based so I guess that's somehow the cause?

Maybe CentOS 6.9 doesn't support the graphics card in your new server?

All that display is done using the most basic video modes available and should work on just about any card.

Is this a UEFI system?

You can add the ks parameters either through 'e' (add new lines if you don't want to add the parameters to the end of kernel/initrd lines), or 'a' from the main menu which will display a convenient "grub append>" prompt. I don't see where the difficulty is.

To update my problem, I found the settings in the UEFI bios to revert it to legacy BIOS system. It behaves as expected using those settings, I get the second screenshot shown above when I boot from CentOS 6.9 dvd. So it's not a video driver issue. CentOS 6.9 iso file apparently behaves differently if you boot from a UEFI system versus BIOS.

Yes, UEFI vs BIOS does look different, but that should not matter. The command line editing functionality is present in both.