In trying to build a custom kickstart ISO for CentOS 8, I'm tripping on getting the installer to run. The ISO is bootable now, but the boot process hangs at where I think the installer should be starting.

In adding the customized kickstart file, I need to edit two files to reference that kickstart file at boot time.

  • For BIOS installations, this page tells me to edit isolinux/isolinux.cfg to add ks=cdrom:/ks.cfg to the ends of the lines starting with append.
  • For UEFI installations, this page suggested editing EFI/BOOT/grub.cfg to add inst.ks=cdrom:/ks.cfg to the ends of the lines starting with linuxefi.

Either or both of those modifcations caused the installer boot process to hang. However, if I added a /ks.cfg to the root of the ISO and executed mkisofs without modifying those files, I could get a default installer. So, something about adding [inst.]ks=cdrom:/ks.cfg to those two files is causing the ISO installer to hang, and the plain existance of the kickstart file is not a factor.


The old ways of doing things don't work in CentOS 8. The range of options for looking up and executing from a kickstart file have expanded. This has forced the inst.ks option to be more detailed than before. The first clue came from Red Hat's Advanced Boot Options documentation. It says,

If you specify a device and not a path, the installation program looks for the Kickstart file in /ks.cfg on the device that you specify.

But, [inst.]ks=cdrom:/ks.cfg doesn't actually specify a device! If you look at those append or linuxefi lines, you'll see an entry for the stage2 installer:


Note that it specifies a device TYPE of hd. The specific hd device for the stage2 installer is identified by LABEL=CentOS-8-3-2011-x86_64-dvd. So, given the Red Hat blockquote above, the CORRECT way to specify the kickstart file named ks.cfg in the root of the ISO is


If you want to use a different name for your kickstart file, you can add


using whatever filename suits your use case. For more information on the format of the ISO boot options, check this out.

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