set ubuntu screen saver idle time
After searching for a very long time, I got some answer at last:
first method is to use gsettings
gsettings set org.gnome.settings-daemon.plugins.power sleep-display-ac 600
gsettings set org.gnome.settings-daemon.plugins.power sleep-display-battery 600
gsettings set org.gnome.desktop.session idle-delay 600
gsettings set org.gnome.desktop.screensaver idle-activation-enabled 'true'
gsettings set org.gnome.desktop.screensaver lock-enabled 'true'
gsettings set org.gnome.desktop.screensaver lock-delay 900
another way is:
vim ~/.gconf/desktop/gnome/%gconf.xml
<?xml version="1.0"?>
<gconf>
<entry name="idle_delay" mtime="1282047258" type="int" value="2"/>
</gconf>
which indicate default idle time is 2
minutes. Interesting!