?wiki:initramfs-tools is used in Debian to build the initramfs that contains the early userspace and the needed kernel modules to be able to mount any possible root.

Boot

Boot with rootdelay=9 to shorten the time of waiting for the root device to come up. Also it adds time to scsi device to settle before calling mdadm or lvm thus excluding potential races.

Debug Howto

Ok now you landed in the initramfs debug shell. The following steps should help to narrow down the problem.