setterm -blank nn will tell the console driver to blank the
screen after nn minutes of inactivity. (With nn = 0, screensaving
is turned off. In some old kernels this first took effect after the next
keyboard interrupt.)
The s option of xset(1) will set the X screensaving parameters.
The video hardware powersaving modes can be enabled/disabled
using the setvesablank program given in the starting comment of
/usr/src/linux/drivers/char/vesa_blank.c.