docs: Remove old cruft from Debian package page

Part of #1398

docs/debian.rst

@@ -26,30 +26,19 @@ Running as a system service
 ===========================
 
 The Debian package comes with an init script. It starts Mopidy as a system
-service running as the ``mopidy`` user, which is created by the package.
+service running as the ``mopidy`` user. The user is created by the package.
 
-The Debian package version 0.18.3-1 and older starts Mopidy as a system
+The Debian package might ask if you want to run Mopidy as a system service. If
-service by default. Version 0.18.3-2 and newer asks if you want to run Mopidy
+you don't get the question, your system is probably configured to ignore
-as a system service, defaulting to not doing so.
+questions at that priority level during installs, and defaults to not enabling
+the Mopidy service.
 
-If you're running 0.18.3-2 or newer, and you've changed your mind about whether
+If you didn't get the question or if you've changed your mind about whether or
-or not to run Mopidy as a system service, just run the following command to
+not to run Mopidy as a system service, just run the following command to
 reconfigure the package::
 
     sudo dpkg-reconfigure mopidy
 
-If you're running 0.18.3-1 or older, and don't want to use the init script to
-run Mopidy as a system service, but instead just run Mopidy manually using your
-own user, you need to disable the init script and stop Mopidy by running::
-
-    sudo update-rc.d mopidy disable
-    sudo service mopidy stop
-
-This way of disabling the system service is compatible with the improved
-0.18.3-2 or newer version of the Debian package, so if you later upgrade to a
-newer version, you can change your mind using the ``dpkg-reconfigure`` command
-above.
-
 
 Differences when running as a system service
 ============================================
@@ -59,20 +48,9 @@ from a regular Mopidy setup you'll want to know about.
 
 - All configuration is in :file:`/etc/mopidy`, not in your user's home
   directory. The main configuration file is :file:`/etc/mopidy/mopidy.conf`.
-  You can do all your changes in this file.
+  This is the configuration file with the highest priority, so it can override
-
+  configs from all other config files. Thus, you can do all your changes in
-- Mopidy extensions installed from Debian packages will sometimes install
+  this file.
-  additional configuration files in :file:`/usr/share/mopidy/conf.d/`. These
-  files just provide different defaults for the extension when run as a system
-  service. You can override anything from :file:`/usr/share/mopidy/conf.d/` in
-  the :file:`/etc/mopidy/mopidy.conf` configuration file.
-
-  Previously, the extension's default config was installed in
-  :file:`/etc/mopidy/extensions.d/`. This was removed with the Debian
-  package mopidy 0.19.4-3. If you have modified any files in
-  :file:`/etc/mopidy/extensions.d/`, you should redo your modifications in
-  :file:`/etc/mopidy/mopidy.conf` and delete the
-  :file:`/etc/mopidy/extensions.d/` directory.
 
 - The init script runs Mopidy as the ``mopidy`` user. The ``mopidy`` user will
   need read access to any local music you want Mopidy to play.
@@ -97,11 +75,6 @@ from a regular Mopidy setup you'll want to know about.
 
       sudo mopidyctl local scan
 
-  Previously, you used ``sudo service mopidy run <subcommand>`` instead of
-  ``mopidyctl``. This was deprecated in Debian package version 0.19.4-3 in
-  favor of ``mopidyctl``, which also work for systems using systemd instead of
-  sysvinit and traditional init scripts.
-
 - Mopidy is started, stopped, and restarted just like any other system
   service::