# [Tex/LaTex] Only name of section in header + underlined

I'm now trying to tweak the headers of my book document. I only need the name of the section in the header and I want it to be underlined and no uppercase letters!

\documentclass{book}
\usepackage[german]{babel}
\usepackage[utf8]{inputenc}
\usepackage{graphicx}
\usepackage{caption}
\usepackage{booktabs,dcolumn}
\usepackage[figureposition=bottom]{caption}
\usepackage{fancyhdr}
\usepackage{underlin}
\pagestyle{fancy}
\fancyhf{}
\newcolumntype{d}[1]{D{.}{.}{#1}}
\newcommand*{\mc}[1]{\multicolumn{1}{c}{#1}}
\newcommand*{\mcTwo}[1]{\multicolumn{2}{c}{#1}}
\setlength\parindent{0pt}
\begin{document}
\chapter {Einleitung}
\section{Motivation}
zz
\clearpage
zz
\end{document}


So, I just need it to be underlined. And to remove Kapitel 1 so just the name of the section.

Note the image in your question does not use the same text as the headings in the source which makes testing a bit difficult, but I think you want something like this. You had loaded fancyhdr but were not using it as you had specified an underline page style defined by a different package. I removed all packages not relevant to the question to make a more _M_inimal example.

\documentclass{book}
\usepackage[german]{babel}
\usepackage[utf8]{inputenc}

\usepackage{fancyhdr}

\fancyhf{}
\pagestyle{fancy}

\renewcommand{\chaptermark}[1]{
\markboth{#1}{}}

\begin{document}
\chapter {Einleitung}
\section{Motivation}
zz
\clearpage
zz
\end{document}