Linux screen brightness / backlight

$ xrandr --output LVDS1 --brightness 0.9

bmark -title="Kernel/Debugging/Backlight - Ubuntu Wiki" https://wiki.ubuntu.com/Kernel/Debugging/Backlight 

bmark -title="Unable to change brightness in Lenovo B570 laptop" http://ubuntuforums.org/showthread.php?t=1827810

bmark -title="Backlight - ArchWiki" https://wiki.archlinux.org/index.php/Backlight

bmark -title="How to change brightness on linux desktop through the command line? - Super User" http://superuser.com/questions/256084/how-to-change-brightness-on-linux-desktop-through-the-command-line

vbmark -title="opensuse - How to change the Monitor brightness on Linux? - Stack Overflow" http://stackoverflow.com/questions/6625836/how-to-change-the-monitor-brightness-on-linux