Comment 10 for bug 1652270

I got the breaking-update automatically via unattended-upgrades -- no human intervention of any kind. Simply rebooted the RPi3 after the holidays and it failed to come back up.

To fix it, I used "qemu-user-static"'s ARM emulation to get a chroot into the SD card's system on my laptop, and then I did "apt-get purge linux-image-4.4.0-1038-raspi2 linux-headers-4.4.0-1038-raspi2 linux-raspi2-headers-4.4.0-1038" so that it'd force the older kernel to be the latest (make sure you do in fact have the older kernel package installed -- "dpkg -l | grep linux-image").

That also purged the "linux-image-raspi2" metapackage, so I'm not likely to get any further automatic kernel updates (which really is a bad thing, given that they're likely to contain security fixes), but until this is fixed, I'm not willing to risk it (need the box to be up and running more urgently).