The system is : Debian 8.1 run on embedded system with ARM7V CPU 2 GB RAM and 4 GB flash.
The system sporadically restart itself couple time in day, before a week with appear very rare.
What is the best way find a reason of such behavior ?
I first would run the last command and see when the restarts were happening, and once I pinpointed a time look in the system logs generally /var/log/messages, that would run out application or OS related issues. POE should be okay, but is the switch powering off the interface? I would also look at the switches logs.