Update Agenda.md

Agenda.md

@@ -49,7 +49,7 @@ Course material repository:  https://gitlab.dkrz.de/pythoncourse/material/
             <li>editor</li>
         </ul>
     </td>
-    <td style="vertical-align:top">  </td>
+    <td style="vertical-align:top"> [intro to linux](./introduction_linux.md) </td>
     <td style="vertical-align:top">1.0</td>
     <td style="vertical-align:top">Jannek<br>practice with Ralf</td>
   </tr>