I only point these things out because I feel it's somewhat irresponsible *ever* to say "Wrong there is no risk. Regardless, this is pretty minor with regard to security. But it's easier now, say, to pull an alley-oop, in which the attacker might install malicious code remotely using a nonauthenticated exploit, and then convince an unauthorized employee over the phone to reboot the server using one of these methods. An Open Firmware password is much stronger against this kind of attack. Of course, this is a very small measure of defense. Wait for a few seconds, then press the power button again to turn on your Mac. Previous security guidelines advised against enabling these buttons, as a small measure of defense against two general scenarios: in one, the attacker has modified binary code on the system by remote means (buffer overflow, filesystem tricks, etc.), and needs to reboot to apply the changes in the other, the attacker wants access to protected data on the machine and intends to reboot from a custom hard disk or CD (think: Knoppix), or put the machine in TDM mode with their laptop. Press and hold the power button for 10 seconds, then release the button. There is *always* some risk associated with allowing a machine to shut down or reboot. And, obviously, you must have unchecked the "Show the Restart, Sleep, and Shut Down buttons" option in that same area.] I just think this seems like a very handy timesaver - note that you must have the "Display login window as" area of the Login Options section of the Accounts preferences pane set to "Name and password" for this to work. If this is a home machine, more than likely the power button on the CPU will be reachable, which would let one do the same thing (without being at the login screen, for that matter). If this is a public kiosk machine, the login screen will be unreachable. Some may claim this is a security hole of sorts I don't believe it is, as being able to shut down or restart from the login screen implies that you can actually reach that screen in the first place. If you don’t want your Mac to completely shut down, you can set your Mac to automatically enter sleep mode instead. [ robg adds: While testing this one, I found you can also use >sleep to enter sleep mode. Do this for both the hard drive device, and your boot volume. Open Disk Utility and use it to run a Repair Disk routine, available in the First Aid tab when you select your hard drive. As far as I can tell, this only works in Tiger. Hold the Command - R keys down at the boot chimes to load your Mac into Recovery Mode. How do you shut down or restart your Mac when you are at the login screen and the Restart and Shut Down buttons are disabled? It's simple just type >shutdown or >restart as the user name, then click the Log In button. First, I must give credit to my colleague for finding this today.
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