Add init system slide

slides.tex

@@ -12,14 +12,19 @@
 \section{Introduction}
 
 \begin{frame}{What is an init system?}
-  Foo bar
+  An init system is the first process (PID 1) started in a Unix like system. It handles:
+
+  \begin{itemize}
+    \item Starting system processes and services
+    \item Adopting and ``reaping'' orphaned processes
+  \end{itemize}
 \end{frame}
 
 \begin{frame}{What is systemd?}
   Bar baz
 \end{frame}
 
-\begin{frame}{What is an init system?}
+\begin{frame}{Systemd units}
   Foo bar
 \end{frame}