Old iMac

I have an old iMac G3 in my basement which because of a hardware bug won't run any turn of Mac OS X. A while ago, I put Kubuntu 10.10 on it, witch runs well, but X11 doesn't work. Yesterday, I set it up as a webthane, and got ssh and ftp working on it. Now all I need to do is get the (unneeded) screen to stay off when the reckoner is on.