<chapter xmlns="http://docbook.org/ns/docbook"
        xmlns:xlink="http://www.w3.org/1999/xlink"
        xmlns:xi="http://www.w3.org/2001/XInclude"
        version="5.0"
        xml:id="sec-writing-documentation">

<title>Writing NixOS Documentation</title>

<para>
  As NixOS grows, so too does the need for a catalogue and explanation
  of its extensive functionality. Collecting pertinent information
  from disparate sources and presenting it in an accessible style
  would be a worthy contribution to the project.
</para>

<section>
<title>Building the Manual</title>
<para>
  The DocBook sources of the <xref linkend="book-nixos-manual"/> are in the
  <link xlink:href="https://github.com/NixOS/nixpkgs/tree/master/nixos/doc/manual"><filename>nixos/doc/manual</filename></link>
  subdirectory of the Nixpkgs repository. If you make modifications to
  the manual, it's important to build it before committing. You can do
  that as follows:

  <screen>nix-build nixos/release.nix -A manual.x86_64-linux</screen>
</para>

<para>
  When this command successfully finishes, it will tell you where the
  manual got generated. The HTML will be accessible through the
  <filename>result</filename> symlink at
  <filename>./result/share/doc/nixos/index.html</filename>.
</para>
</section>

<section>
<title>Editing DocBook XML</title>

<para>
  For general information on how to write in DocBook, see
  <link xlink:href="http://www.docbook.org/tdg5/en/html/docbook.html">
    DocBook 5: The Definitive Guide</link>.
</para>

<para>
  Emacs nXML Mode is very helpful for editing DocBook XML because it
  validates the document as you write, and precisely locates
  errors. To use it, see <xref linkend="sec-emacs-docbook-xml"/>.
</para>

<para>
  <link xlink:href="http://pandoc.org">Pandoc</link> can generate
  DocBook XML from a multitude of formats, which makes a good starting
  point.

  <example xml:id="ex-pandoc-xml-conv">
    <title>Pandoc invocation to convert GitHub-Flavoured MarkDown to DocBook 5 XML</title>
    <screen>pandoc -f markdown_github -t docbook5 docs.md -o my-section.md</screen>
  </example>

  Pandoc can also quickly convert a single
  <filename>section.xml</filename> to HTML, which is helpful when
  drafting.
</para>

<para>
  Sometimes writing valid DocBook is simply too difficult. In this
  case, submit your documentation updates in a <link
  xlink:href="https://github.com/NixOS/nixpkgs/issues/new">GitHub
  Issue</link> and someone will handle the conversion to XML for you.
</para>
</section>

<section>
<title>Creating a Topic</title>

<para>
 You can use an existing topic as a basis for the new topic or create a topic from scratch.
</para>

<para>
Keep the following guidelines in mind when you create and add a topic:

<itemizedlist>
  <listitem><para>
    The NixOS <link xlink:href="http://www.docbook.org/tdg5/en/html/book.html"><tag>book</tag></link>
    element is in <filename>nixos/doc/manual/manual.xml</filename>.
    It includes several
    <link xlink:href="http://www.docbook.org/tdg5/en/html/book.html"><tag>part</tag>s</link>
    which are in subdirectories.
  </para></listitem>

  <listitem><para>
    Store the topic file in the same directory as the <tag>part</tag>
    to which it belongs. If your topic is about configuring a NixOS
    module, then the XML file can be stored alongside the module
    definition <filename>nix</filename> file.
  </para></listitem>

  <listitem><para>
    If you include multiple words in the file name, separate the words
    with a dash. For example: <filename>ipv6-config.xml</filename>.
  </para></listitem>

  <listitem><para>
    Make sure that the <tag>xml:id</tag> value is unique. You can use
    abbreviations if the ID is too long. For example:
    <varname>nixos-config</varname>.
  </para></listitem>

  <listitem><para>
    Determine whether your topic is a chapter or a section. If you are
    unsure, open an existing topic file and check whether the main
    element is chapter or section.
  </para></listitem>

</itemizedlist>

</para>
</section>

<section>
<title>Adding a Topic to the Book</title>

<para>
  Open the parent XML file and add an <varname>xi:include</varname>
  element to the list of chapters with the file name of the topic that
  you created. If you created a <tag>section</tag>, you add the file to
  the <tag>chapter</tag> file. If you created a <tag>chapter</tag>, you
  add the file to the <tag>part</tag> file.
</para>

<para>
  If the topic is about configuring a NixOS module, it can be
  automatically included in the manual by using the
  <varname>meta.doc</varname> attribute. See <xref
  linkend="sec-meta-attributes"/> for an explanation.
</para>

</section>






</chapter>
