diff --git a/content.tex b/content.tex
index 63ba0d7..9dfb6e8 100644
--- a/content.tex
+++ b/content.tex
@@ -149,12 +149,24 @@ KERNEL=="i2c-1", MODE="0777"
 To enable spi interface edit \texttt{/boot/config.txt}. \\
 Uncomment \texttt{\#device\_tree\_param=spi=on}
 
+\subsubsection{GPIO}
+Create an udev rule to enable others than root accessing the gpio files:
+\begin{lstlisting}
+/etc/udev/rules.d/98-gpio.rules
+
+SUBSYSTEM=="gpio*", PROGRAM="/bin/sh -c 'chown -R root:gpio\
+/sys/class/gpio; chmod -R 0777 /sys/class/gpio; chown -R \
+root:gpio /sys/devices/virtual/gpio; chmod -R 0777 \
+/sys/devices/virtual/gpio'"
+\end{lstlisting}
+
 \subsection{tools}
 \begin{itemize}
 \item \texttt{fakeroot}
 \item \texttt{gcc}
 \item \texttt{git}
 \item \texttt{make}
+\item \texttt{patch}
 \item \texttt{python2, python2-pip}
 \item \texttt{wget}
 \end{itemize}