You can also use xmodmap [1].

My xmodmap file has things like:

  ! Make Caps Lock be Escape and Scroll Lock be Caps Lock
  remove Lock = Caps_Lock
  keysym Caps_Lock = Escape
  remove Lock = Scroll_Lock
  keysym Scroll_Lock = Caps_Lock
  add Lock = Caps_Lock

After reading this post, I also reverted backspace and bar/backslash:

  keysym BackSpace = backslash bar
  keysym backslash = BackSpace

[1] https://wiki.archlinux.org/index.php/Xmodmap

EDIT: xmodmap link