I'm not the administrator, so I'm not in the sudo list. How can I shut down the computer from command line without sudo? As I can shut down the computer from GUI, I must be able to get the privilege from somewhere... Thanks.
The privilege to shut down or restart without root is managed by ConsoleKit.
While the mechanism for how this works is changing as a result of systemd and logind, sending the following ConsoleKit message should still work to shut down without root:
/usr/bin/dbus-send --system --print-reply --dest="org.freedesktop.ConsoleKit" /org/freedesktop/ConsoleKit/Manager org.freedesktop.ConsoleKit.Manager.Stop