I was updating a remote pi when it was powered down in the midst. After it was rebooted, it only gives 7 flashes which I think translates to "unable to find/load kernel.img". I took out the sd-card mounted it on a laptop running Debian and /boot has start.elf and boocode.bin but no kernel.img (also no kernel7.img). So, now I am thinking that perhaps I could attempt to boot a kernel placed there manually and then use apt and dpkg to finish try to salvage the broken install. However, I wonder where I could get a precompiled Raspbian kernel.img?
EDIT: it appears I found it.