[ubuntu] How to disable suspend / screen blank when lid closes ?

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http://ubuntuforums.org – I want to disable suspend/ screen blank so that the laptop (ASUS F6J running Karmic 9.10) remains on once the lid is closed. I use a monitor plugged into the laptop when I work at home and want to stack the laptop on a small shelf. I use the machine on ac power all the time to am not worried about batteries. I have switched of the laptop screen in System/Preferences/Display but naturally enough it still suspends when the lid is closed. If possible it would be best if the screen remain off while the machine is running with the lid down.I have been able to to this using FreeBSD and did no (Hardware)