A note to the enforced rebooting of 3.0 / 3.1 systems, a possible cause is,
in addition to the kernel config, the device tree configuration of the tegra watchdog timer. Since version 3.0 the timer´s heartbeat is set to 120 seconds.
Within this time interval the system software, e.g. systemd, has to send at least
one ping to the watchdog device, otherwise the system reboots after a hardware
reset. In order to avoid that with systemd, in /etc/systemd/system.conf the option RuntimeWatchdogSec must be set to a non-zero value, e.g. 40s :
(See man page of systemd-system.conf)
systemd will now send a ping to the hardware every 20 seconds.
Perfect, you saved my day! Now it runs stable and smooth. I had to tweak also /etc/resolv.conf from Xenial image to make networking work.
However, all kernels seem to be running single core only. /proc/cpuinfo reports only one processor. Is there any tweak to utilize all 8 cores of A57 & A53?