> Gotta ask though...hypervisors for cars??? Why? (That is a genuine question)
Exactly. I used to do automotive (8-bit micros, Lucas Automotive, first rolling and temporally coded remote locking). I made sure if you ran a coarse file across between the battery terminal and the terminal clamp it was supposed to connect to making lots of electronics very unhappy and things under the bonnet click our unit would still recover with the correct alarm state and let you start the car (if unlocked of course). Modern stuff is bloated enough with heavy operating systems. Why anybody would want to introduce a hypervisor, which let's face it is just operating system spaghetti, beats me.
As for backups as somebody said snapshotting at the block device level might work but isn't really satisfactory. How about ZFS or another filesystem with snapshotting built-in ?