The i3 window manager, the 2017 Thinkpad X1 Carbon, and XF86MonBrightnessUp XF86MonBrightnessDown

Here is how to get the Fn F6 and Fn F5 keys working on a brand new 2017 Thinkpad X1 Carbon.

The keys are already correctly mapped to, respectively, XF86MonBrightnessUp and XF86MonBrightnessDown, but there is nothing assigned to these keys. Try this:

A create a /etx/X11/xorg.conf with

Section "Device"
    Identifier  "Card0"
    Driver      "intel"
    Option      "Backlight"  "intel_backlight"
EndSection

See Debian bug #651741 for some more information.

B in ~/.i3/conf add:

bindsym XF86MonBrightnessDown exec "xbacklight -dec 10"
bindsym XF86MonBrightnessUp exec "xbacklight -inc 10"

See pastebin code

C Restart i3 with Mod R, or restart X.