* Document DHCP preseeding. Note that this documents it as of netcfg 1.24

  and preseed 1.13.

1 files changed, 38 insertions, 5 deletions

diff --git a/en/appendix/preseed.xml b/en/appendix/preseed.xml
index 3c6b0110b..2fa067b3e 100644
--- a/en/appendix/preseed.xml
+++ b/en/appendix/preseed.xml
@@ -278,11 +278,11 @@ load it.
 
 </para><para>
 
-For the other preseeding methods you need to tell the installer what file to
-use when you boot it. This is done by passing the kernel a boot parameter,
-either manually at boot time or by editing the bootloader configuration file
-(e.g. <filename>syslinux.cfg</filename>) and adding the parameter to the end
-of the append line(s) for the kernel.
+For the other preseeding methods you need to tell the installer what file
+to use when you boot it. This is normally done by passing the kernel a boot
+parameter, either manually at boot time or by editing the bootloader
+configuration file (e.g. <filename>syslinux.cfg</filename>) and adding the
+parameter to the end of the append line(s) for the kernel.
 
 </para><para>
 
@@ -323,6 +323,39 @@ questions even if the preseeding below misses some.
 
 </para>
   </sect2>
+  
+  <sect2 id="preseed-dhcp">
+  <title>Using a DHCP server to specify preseed files</title>
+<para>
+
+It's also possible to use DHCP to specify a preseed file to download from
+the network. DHCP allows specifying a filename. Normally this is a file to
+netboot, but it it appears to be an URL then installation media that
+support network preseeding will download the file from the URL and use it
+as a preseed file. Here is an example of how to set it up in the dhcpd.conf
+for version 3 of the ISC DHCP server (the dhcp3-server Debian package).
+
+</para>
+
+<informalexample><screen>
+if substring (option vendor-class-identifier, 0, 3) = "d-i" {
+	filename "http://host/preseed.cfg";
+}
+</screen></informalexample>
+
+<para>
+Note that the above example limits this filename to DHCP clients that identify
+themselves as "d-i", so it will not affect regular DHCP clients, but only
+the installer. You can also put the text in a stanza for only one particular
+host to avoid preseeding all installs on your network.
+
+</para><para>
+A good way to use the DHCP preseeding is to only preseed values specific to
+your network, such as the Debian mirror to use. This way installs on your
+network will automatically get a good mirror selected, but the rest of the
+installation can be performed interactively. Using DHCP preseeding to fully
+automate Debian installs should only be done with care.
+</para>
 
   <sect2 id="preseed-bootparms">
   <title>Using boot parameters to supplement preseeding</title>