.xmodmap

 ! undo any meta keys already set
 clear Mod1
 
 ! keycodes 63 and 71 are the left and right COMMAND buttons adjacent to the spacebar; set them to be control keys
 keycode 63 = Control_L
 keycode 71 = Control_R
 
 ! keycodes 66 and 69 are the option/alt keys; assign them as Meta keys
 keycode 66 = Escape NoSymbol Escape
 keycode 69 = Meta_R
 
 ! now tell X11 that the Meta keys act as the Mod1 (meta) modier key; that is, when they are pressed with KEY, it is the same as hitting M-KEY
 add Mod1 = Meta_L Meta_R
 
 ! tell X11 that the Control keys are Control modifiers, so when pressed with u (for example) it is the same as hitting C-u
 add Control = Control_L Control_R