# gsettings get org.gnome.desktop.session idle-delay
# gsettings get org.gnome.desktop.screensaver lock-delay
# gsettings get org.gnome.desktop.screensaver lock-enabled
change the settings
# gsettings set org.gnome.desktop.session idle-delay 180
# gsettings set org.gnome.desktop.screensaver lock-delay 300
# gsettings set org.gnome.desktop.screensaver lock-enabled true