Thank you for the answer, but now i have a problem with screenblank. it 
is started at boot, after the inactivity-timeout, it shut down the 
screen, but when i hit the keyboard, nothing happen on the four 
terminals. i must start X  to relight my screen ? i have read the man 
page and the frame buffer device don't exist. when i try to ./MAKEDEV fb 
it answer to me " unknown device".

anybody have an idea.