/usr/lib/x86_64-linux-gnu/libnss_files.so is in libc6-dev 2.19-0ubuntu6.
This file is owned by root:root, with mode 0o777.
It is a symlink to /lib/x86_64-linux-gnu/libnss_files.so.2
/lib/x86_64-linux-gnu/libnss_files.so.2