Install

Install xbindkeys:

• For ArchLinux: pacman -S xbindkeys;
• For i3 on Ubuntu: sudo apt install xbindkeys xbacklight.

Usage

1. Start xbindkeys when X startup: for ArchLinux: add xbindkeys before "exec i3" in ~/.xinitrc; for i3 on Ubuntu: add xbindkeys into ~/.xsessionrc;

2. Get a template: xbindkeys -d > ~/.xbindkeysrc;

3. Detect key definition: xbindkeys -k;

4. Add output from last command to ~/.xbindkeysrc;

5. Reload new configs: pkill xbindkeys; xbindkeys;

6. Verify the setup.

As an example, add the following lines into ~/.xbindkeysrc to increase and decrease LCD brightness of Thinkpad T440p:

"xbacklight -dec 10"
    XF86MonBrightnessDown

"xbacklight -inc 10"
    XF86MonBrightnessUp

Ref:

• Xbindkeys

• http://www.butlerpc.net/blog/2011/01/using-xbindkeys-on-ubuntu-linux-to-remap-key-commands/