\input{preambule}
\begin{document} 
  \maketitle
  \setcounter{secnumdepth}{5} % a virer
  \etocsetnexttocdepth{5} % à virer
  \tableofcontents % idem
  \frontmatter
    \input{frontmatter}
  \mainmatter
   \input{mainmatter}
  \backmatter
    \input{backmatter}
\end{document}