//shutdown 關機命令/重啟/取消
(root 權限)
shutdown /*好慢，要等一會*/
sudo shutdown -h now
sudo poweroff

sudo halt

shutdown -r
sudo shutdown -r now
sudo reboot

shutdown -c
sudo shutdown -c

For Ubuntu 15.04 and later:
(This is due to Ubuntu's shift in using systemd instead of Upstart)

systemctl poweroff

systemctl reboot

systemctl suspend

systemctl hibernate

systemctl hybrid-sleep
Since hibernate is normally disabled by default in Ubuntu systems, you can enable this by checking this answer: http://askubuntu.com/a/617254/101985