I needed to build an initrd image and a complementary boot disk with support for my scsi card and for raid0. In the process I noticed that mkinitrd and mkbootdisk work slightly differently and don't agree completely with their respective man pages. Man page for mkinitrd mkinitrd [-fv] [--with=module] [--preload=module] [--omit-scsi-modules] [--version] image kernel-version when executing program however it seems to prefer "--with module" (in my case --with raid0) while man page for mkbootdisk says mkbootdisk [--version] [--noprompt] [--verbose] [--mkinitrdargs <args>] [--device <devicefile>] <kernel> When executing mkbootdisk I found that I needed to specify the initrd options as "--mkinitrdargs --with=module" (here I used --mkinitrdargs --with=raid0)
mkinitrd accepts both --with=foo and --with foo; it always has (according to my reading of our version control logs) and I just tested to make sure that it works.