/usr/bin/thumbpdf is in texlive-latex-recommended 2015.20160320-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/bin/../share/texlive/texmf-dist/scripts/thumbpdf/thumbpdf.pl
/usr/bin/../share/texlive/texmf-dist/scripts/thumbpdf/thumbpdf.pl