How do I switch of the powersave options (screen off etc.)
 

I am running Ubuntu on a mythtv platform. I newly upgraded and switched to fluxbox. I now have this small problem that after some time the screen goes dark and after some time more it completely switches of. I suppose these are also regulated under ACPI? How can I change this stuff from command line since most of the time I do configurating from a second PC via ssh...

'xset -dpms' will disable the energy star features of the monitor (and 'xset +dpms' will turn them back on). There are other options as well, so please check the xset man page.