/usr/share/doc/texlive-doc/luatex/lua-visual-debug/strut.png is in texlive-luatex 2012.20120611-5.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/texlive-doc/luatex/lua-visual-debug/../../../texlive-luatex/luatex/lua-visual-debug/strut.png