# mkinitrd /boot/initrd-2.6.18-194.el5.img `uname -r` -f

# command to include a module
mkinitrd -v -f /boot/initrd-`uname -r`.img `uname -r` --preload=scsi_dh_rdac
# -f /boot/initrd-`uname -r`.img is the new initrd you are creating and -f says to overwrite if it exists.
# `uname -r` means create an initrd to suit the currently running kernel

# command to check if initrd has a specific module
zcat initrd-2.6.18-194.el5.img | cpio -it| grep -i scsi_dh_rdac