/usr/lib/x86_64-linux-gnu/liblua5.1-posix.so is in lua-posix-dev 31-2build1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/liblua5.1-posix.so.1.0.0
/usr/lib/x86_64-linux-gnu/liblua5.1-posix.so.1.0.0