/usr/share/texmf/web2c/texmf.cnf is in texlive-base 2017.20180305-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/texmf/web2c/../../texlive/texmf-dist/web2c/texmf.cnf
/usr/share/texmf/web2c/../../texlive/texmf-dist/web2c/texmf.cnf