$ gsettings set org.gnome.settings-daemon.plugins.power button-power 'suspend'
$ gsettings set org.gnome.settings-daemon.plugins.power power-button-action 'suspend'
sudo su --login gdm --shell /bin/bash
gdm$ dbus-launch --exit-with-session gsettings set org.gnome.settings-daemon.plugins.power button-power 'suspend'