added 0.13.0 config check to install docs

docs/admin/install.rst

@@ -10,6 +10,7 @@ SecureDrop Workstation must be installed on a system running Qubes OS. The insta
 Pre-install tasks:
 ~~~~~~~~~~~~~~~~~~
 
+#. Verify the SecureDrop server configuration
 #. Apply BIOS updates and check settings
 #. Download and verify Qubes OS
 #. Install Qubes OS
@@ -47,6 +48,34 @@ A basic knowledge of the Qubes OS is helpful.
 Pre-install tasks
 -----------------
 
+Verify the SecureDrop server configuration
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+In order to be used with SecureDrop Workstation, your instance must be running the latest version of SecureDrop, and the server configuration must have been updated to allow for HTTP ``DELETE`` requests. The configuration change to enable this was added in the ``0.13.0`` version of SecureDrop, released on May 29 2019. If your instance was created using this or a later version, it has the necessary changes. If not, then the ``./securedrop-admin install`` command must have been run from an Admin Workstation updated with the ``0.13.0`` code or later. To check this:
+
+- Use an Admin Workstation USB to boot into Tails, with the persistent volume unlocked and an administration password set.
+- Navigate to **Applications ▸ System Tools ▸ Terminal** to open a terminal.
+- Verify that the *Journalist Interface* Apache configuration allows for HTTP ``DELETE`` using the following command:
+
+  .. code-block:: sh
+
+    ssh app "sudo cat /etc/apache2/sites-enabled/journalist.conf | grep '^  <LimitExcept GET POST HEAD DELETE>$'"
+
+- If your instance is configured correctly, this command will output two lines as follows:
+
+  .. code-block:: none
+
+     <LimitExcept GET POST HEAD DELETE>
+     <LimitExcept GET POST HEAD DELETE>
+
+- If not, then you will need to:
+
+  - Update the Admin Workstation to the current SecureDrop release version.
+  - Back up the SecureDrop instance.
+  - Verify that the configuration stored on the Admin Workstation is correct by running ``./securedrop-admin sdconfig``.
+  - Update the instance configuration by running ``./securedrop-admin install``.
+
+- When the instance configuration is up to date, continue with the SecureDrop Workstation installation.
+
 Apply BIOS updates and check settings
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 Before beginning the Qubes installation, make sure that your Qubes-compatible computer's BIOS is updated to the latest available version. If you're using the recommended ThinkPad T480, see the :ref:`t480_bios` section in this documentation. The process will be different for other makes and models, and can usually be found on their respective support sites.