When the power comes back, your server will remain quiet unless you tell your servers to come back to life by themselves.
There are 2 things you must do in the BIOS to make this happen.
- Tell the server to bootup after a power failure. This is the AC Power Loss Restart option in the BIOS. This should be set to On.
- Ignore a missing keyboard. There is an area in the BIOS that handles halting on errors. It should be set so that it ignores keyboard errors. If this is not ignored, the server will wait for the user to press F1.