In the script /etc/grml/fai/grml/grml_cleanup_chroot, the latest kernel version is detected by 
looking in the /lib/modules/ and reverse sorting the entries by locale. This hits a bug when 
directories that are not associated with a specific kernel version are placed in /lib/modules. I 
patched this file to look at /boot/vmlinuz-* rather than /lib/modules. My patch does expect the 
kernel image to start with vmlinuz, but this should be a safe assumption as this is they way 
kernel-package will name the file. Like the original method, it is locale dependent. 

I am attaching the patch.