http://hints.macworld.com/article.php?s ... 3213256255down 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.
ak toto nie, obycajny Power button?
COMMAND + Q can quit the welcome screen and shut it down.
Google:
os x shutdown from login screen