Say I have a log which captures something really interesting as happening during boot. I want to know, was it just a reboot, or complete power off-and-on. What are the definite signs of cold reboot?
Unless the server has an out of band management system like IPMI I dont think there is any way to tell the difference between a reboot by hitting the reset button and a power off.
If it was a reboot done by the OS that will be in the logs right before the reboot. Same if you told the os to shutdown.
So if the power cycle was done through the os it will be in the logs. Might even show it in the output of who or last.