As opções em questão parecem estar definidas no próprio kernel. Esta documentação do kernel abrange:
rd.lvm.lv=
only activate the logical volumes with the given name. rd.lvm.lv can be specified multiple times on the kernel command line.
rd.luks=0
disable crypto LUKS detection
rd.luks.uuid=
only activate the LUKS partitions with the given UUID. Any "luks-" of the LUKS UUID is removed before comparing to . The comparisons also matches, if is only the beginning of the LUKS UUID, so you don’t have to specify the full UUID. This parameter can be specified multiple times.
rd.md=0
disable MD RAID detection
rd.md.imsm=0
disable MD RAID for imsm/isw raids, use DM RAID instead
rd.md.ddf=0
disable MD RAID for SNIA ddf raids, use DM RAID instead
rd.md.conf=0
ignore mdadm.conf included in initramfs
rd.md.waitclean=1
wait for any resync, recovery, or reshape activity to finish before continuing
rd.md.uuid=
only activate the raid sets with the given UUID. This parameter can be specified multiple times.
rd.lvm.uuid
parece não ser suportado.