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diff --git a/nixpkgs/nixos/doc/manual/from_md/development/assertions.section.xml b/nixpkgs/nixos/doc/manual/from_md/development/assertions.section.xml
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--- a/nixpkgs/nixos/doc/manual/from_md/development/assertions.section.xml
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@@ -1,58 +0,0 @@
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xml:id="sec-assertions">
-  <title>Warnings and Assertions</title>
-  <para>
-    When configuration problems are detectable in a module, it is a good
-    idea to write an assertion or warning. Doing so provides clear
-    feedback to the user and prevents errors after the build.
-  </para>
-  <para>
-    Although Nix has the <literal>abort</literal> and
-    <literal>builtins.trace</literal>
-    <link xlink:href="https://nixos.org/nix/manual/#ssec-builtins">functions</link>
-    to perform such tasks, they are not ideally suited for NixOS
-    modules. Instead of these functions, you can declare your warnings
-    and assertions using the NixOS module system.
-  </para>
-  <section xml:id="sec-assertions-warnings">
-    <title>Warnings</title>
-    <para>
-      This is an example of using <literal>warnings</literal>.
-    </para>
-    <programlisting language="bash">
-{ config, lib, ... }:
-{
-  config = lib.mkIf config.services.foo.enable {
-    warnings =
-      if config.services.foo.bar
-      then [ ''You have enabled the bar feature of the foo service.
-               This is known to cause some specific problems in certain situations.
-               '' ]
-      else [];
-  }
-}
-</programlisting>
-  </section>
-  <section xml:id="sec-assertions-assetions">
-    <title>Assertions</title>
-    <para>
-      This example, extracted from the
-      <link xlink:href="https://github.com/NixOS/nixpkgs/blob/release-17.09/nixos/modules/services/logging/syslogd.nix"><literal>syslogd</literal>
-      module</link> shows how to use <literal>assertions</literal>.
-      Since there can only be one active syslog daemon at a time, an
-      assertion is useful to prevent such a broken system from being
-      built.
-    </para>
-    <programlisting language="bash">
-{ config, lib, ... }:
-{
-  config = lib.mkIf config.services.syslogd.enable {
-    assertions =
-      [ { assertion = !config.services.rsyslogd.enable;
-          message = &quot;rsyslogd conflicts with syslogd&quot;;
-        }
-      ];
-  }
-}
-</programlisting>
-  </section>
-</section>