How to check BBB CPU temperature?



I met problem that the BBB got reboot unusually and doubt it is the CPU temp was too high.
Could you tell me how to check the CPU temp with debian 9.5 and which kind of log can help to debug such problem?


@springzhang, the chip used on the BBB is the AM3358BZCZ100, which is rated for 0-90C, what is the temperature of the environment that you installed the board? The “onboard” Temp Sensor is not available in the current software stack, as it was unreliable. Plug in a serial adapter into J1 and log serial events to see why it’s actually rebooting. The default version of u-boot will dump the Reset Registers, so we can also see what triggered the reset.