PXE boot: add manual section and note in changelog

nixos/doc/manual/installation/installing-pxe.xml

@@ -0,0 +1,48 @@
+<section 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-booting-from-pxe">
+
+<title>Booting from the <quote>netboot</quote> media (PXE)</title>
+<para>
+  Advanced users may wish to install NixOS using an existing PXE or
+  iPXE setup.
+</para>
+<para>
+  These instructions assume that you have an existing PXE or iPXE
+  infrastructure and simply want to add the NixOS installer as another
+  option. To build the necessary files from a recent version of
+  nixpkgs, you can run:
+</para>
+<programlisting>
+nix-build -A netboot nixos/release.nix
+</programlisting>
+<para>
+  This will create a <literal>result</literal> directory containing: *
+  <literal>bzImage</literal> – the Linux kernel *
+  <literal>initrd</literal> – the initrd file *
+  <literal>netboot.ipxe</literal> – an example ipxe script
+  demonstrating the appropriate kernel command line arguments for this
+  image
+</para>
+<para>
+  If you’re using plain PXE, configure your boot loader to use the
+  <literal>bzImage</literal> and <literal>initrd</literal> files and
+  have it provide the same kernel command line arguments found in
+  <literal>netboot.ipxe</literal>.
+</para>
+<para>
+  If you’re using iPXE, depending on how your HTTP/FTP/etc. server is
+  configured you may be able to use <literal>netboot.ipxe</literal>
+  unmodified, or you may need to update the paths to the files to
+  match your server’s directory layout
+</para>
+<para>
+  In the future we may begin making these files available as build
+  products from hydra at which point we will update this documentation
+  with instructions on how to obtain them either for placing on a
+  dedicated TFTP server or to boot them directly over the internet.
+</para>
+
+</section>