GUI内终端执行如下指令，或者加入开机启动脚本内

gsettings set org.gnome.settings-daemon.plugins.power button-power shutdown

will change your the behaviour of the power button of your system from interactive (default) to immediate normal shutdown.

The command is gsettings set org.gnome.settings-daemon.plugins.power button-power <option>

Available options are:

• blank: does nothing
• suspend: makes your system suspend
• shutdown: starts a normal issued shutdown procedure
• hibernate: hibernates your system
• nothing: does nothing
• log out: log your user out