After installing Xubuntu 14.04 on my Thinkpad W510, generating /etc/X11/xorg.conf with nvidia-settings and adding the EnableBrightnessControl line to the Devices section and rebooting did not work (it worked in Xubuntu 12.10). Instead, I had to create a /usr/share/X11/xorg.conf.d/10-nvidia-brightness.conf file and add the Devices section to that. It's described in this blog post:
For my future reference, and possibly others:
After installing Xubuntu 14.04 on my Thinkpad W510, generating /etc/X11/xorg.conf with nvidia-settings and adding the EnableBrightnes sControl line to the Devices section and rebooting did not work (it worked in Xubuntu 12.10). Instead, I had to create a /usr/share/ X11/xorg. conf.d/ 10-nvidia- brightness. conf file and add the Devices section to that. It's described in this blog post:
http:// blog.pearce. org.nz/ 2012/08/ enabling- external- monitor- on-lenovo. html
You should probably change the BoardName to whatever it is for your system (mine is "Quadro FX 880M").