In /boot/grub/menu.lst, duplicate from

title          Debian GNU/Linux, kernel 2.6.11-1-k7
root           (hd0,5)
kernel         /boot/vmlinuz-2.6.11-1-k7 root=/dev/sda6 ro
initrd         /boot/initrd.img-2.6.11-1-k7
savedefault
boot

to

title          Debian Sarge with GRML kernel
root           (hd0,5)
kernel         (hd0,2)/boot.grml/isolinux/linux26 root=/dev/sda6 ro
initrd         /boot/initrd.img-2.6.11-1-k7
savedefault
boot

$ dir /lib/modules/
drwxr-xr-x   6 root root 472 04-01 10:05 2.6.11-1-k7/

mount /dev/sda7 /mnt/os1/
rsync -vua /mnt/os1/lib/modules/ /lib/modules/

$ dir /lib/modules/
drwxr-xr-x   6 root root 472 04-01 10:05 2.6.11-1-k7/
drwxr-xr-x  12 root root 712 07-09 16:09 2.6.16-grml/

documented on: 2006.07.10