What's the difference between restarting a machine using the ipmitool subcommands
chassis power cycle versus
chassis power reset?
Reset does a warm boot. Cycle completely powers off the machine then powers it back on, which has the server go through a cold boot.
Here is an explanation in terms of power stats. It comes from here: http://software.intel.com/en-us/forums/showthread.php?t=80403
The "Reset" command performs a warm-reset. The equivalent to the old Ctrl-Alt-Del in DOS. The "power cycle reset" is the same as pressing the power button to turn the machine off, followed by pressing the power button again to turn the machine on. It actually forces the system to transition from a S0 state to a S5 state and back to a S0 state. The "Reset" just transitions from S0 to S0 again. In some cases, the BIOS may require a power off to reload the BIOS if you've updated the BIOS. The PCR can do that, but the simple Reset can't.
The same as the difference between pushing the reset button and power off + power on, i.e. when using reset you skip some of the POST (power on self test).