Unable to find LuCi controller file under /lua/luci

Hi All,

I am trying to change openwrt LuCi web content from target board (The image is compiled after enabling LuCI in the "make menuconfig" configuration menu), but I can't find Luci "controller" folder under /usr/lib/lua/luci directory as suggested by others. Under "/usr/lib/lua/luci" directory, I can only see cbi/ mode/ sys/ template/ tools/ and view/ folders.

Infor:
DISTRIB_RELEASE='SNAPSHOT'
DISTRIB_REVISION='r23414-ed816fba8'

Please advice, thanks.