chg: [documentation] Added information about how to start the website…

… with systemd.

docs/installation.rst

@@ -207,3 +207,37 @@ You can stop it with
 
 With the default configuration, you can access the web interface on http://0.0.0.0:10001,
 where you will find the API and can start playing with it.
+
+
+Launching the website with systemd
+----------------------------------
+
+Create a file ``/etc/systemd/system/vulnerability-lookup-web.service`` with the following contents:
+
+
+.. code-block:: ini
+
+    [Unit]
+    Description=Vulnerability Lookup webservice
+    After=network.target
+
+    [Service]
+    User=<username>
+    WorkingDirectory=/home/<username>/vulnerability-lookup
+    ExecStart=/bin/sh -c '<path-to-virtualenv>/bin/gunicorn -b 127.0.0.1:5000 -w 4 website.app'
+    Restart=always
+
+    [Install]
+    WantedBy=multi-user.target
+
+
+- Appropriately adjust the ``User`` and ``WorkindDirectory``
+- Replace ``<path-to-virtualenv>`` with the path indicated by the command ``poetry shell``.
+
+
+.. code-block:: bash
+
+    $ sudo systemctl daemon-reload
+    $ sudo systemctl enable vulnerability-lookup-web.service
+    $ sudo systemctl start vulnerability-lookup-web.service
+    $ systemctl status vulnerability-lookup-web.service