drakboot "INTERNAL ERROR: unknown device"

1: obviously, run strace drakboot > /tmp/trace 2>&1

2: less /tmp/trace, look for the missing device (in my case it was sdd):

 openat(AT_FDCWD, "/boot/grub2/install.sh", O_RDONLY|O_LARGEFILE|O_CLOEXEC) = 12

ioctl(12, TCGETS, 0xbfb7147c)           = -1 ENOTTY (Inappropriate ioctl for device)

_llseek(12, 0, [0], SEEK_CUR)           = 0

fstat64(12, {st_mode=S_IFREG|0755, st_size=22, ...}) = 0

read(12, "grub2-install /dev/sdd", 8192) = 22

read(12, "", 8192)                      = 0

3: edit /boot/grub2/install.sh and replace the wrong disk reference.

Push-button ON/OFF

In order to start the Peltier-based car freezer and to make sure that it turn off and stays OFF after the car stopped (a big Peltier is a huge battery drain!), I've made this 4-relay based circuit. No or "as little as possible" electronics in the car is the best approach - only the aerospace is harder for electronics than automotive - the best solution might involve some relays and, maybe, a couple of diodes, but stay away from amateurish electronics in the car! This is the diagram I draw on the back of a napkin (as usual) :)