Underlining section titles [duplicate]

Question

Is there a good way by specifying it in the preamble, to underline my section titles (not chapter titles), instead of having to do \chapter{\underline{Section Title}} for all chapter titles in the body?

I would like it as something like in this picture below:

Thanks!

Answer 1

This is a quick way using sectsty

\documentclass{book}
\usepackage{sectsty}
\sectionfont{\underline\normalfont\normalsize\centering}
\usepackage{lipsum}
\begin{document}
\chapter{This is a chapter}
\section{This is your section}
\lipsum[1]
\end{document}