/usr/ is in libgfsgl-dev 20121130+dfsg-1build2.
This file is owned by root:root, with mode 0o755.
..
/usr/include/
/usr/include/gerris/
/usr/include/gerris/batch/
/usr/include/gerris/batch/render.h
/usr/include/gerris/gl/
/usr/include/gerris/gl/gfsgl2D.h
/usr/include/gerris/gl/gfsgl3D.h
/usr/include/gerris/gl/gfsgl.h
/usr/include/gerris/gl/trackball.h
/usr/include/gerris/view/
/usr/include/gerris/view/gfkgl3D.h
/usr/include/gerris/view/gfkgl.h
/usr/include/gerris/view/glade/
/usr/include/gerris/view/glade/interface.h
/usr/include/gerris/view/glade/callbacks.h
/usr/include/gerris/view/glade/support.h
/usr/include/gerris/view/gfkgl2D.h
/usr/share/
/usr/share/doc/
/usr/share/doc/libgfsgl-dev/
/usr/share/doc/libgfsgl-dev/copyright
/usr/lib/
/usr/lib/x86_64-linux-gnu/
/usr/lib/x86_64-linux-gnu/gerris/
/usr/share/doc/libgfsgl-dev/changelog.Debian.gz
/usr/lib/x86_64-linux-gnu/libgfsgl2D.so
/usr/lib/x86_64-linux-gnu/gerris/libgfsview2D.so
/usr/lib/x86_64-linux-gnu/gerris/libgfsview3D.so
/usr/lib/x86_64-linux-gnu/libgfsgl3D.so