Need explanations about server-name, next-server...

[Jeremie Le Hen]

Hi list,

On Sun, Mar 04, 2007 at 08:49:40PM +0100, Jeremie Le Hen wrote:
> I have been looking for PXE HOWTOs and I saw numerous options that
> seems to overlap themselves.  I've read what I could in dhcpd.conf(5)
> manpage and glanced at RFC1533 as well but I'm still bewildered.
> 
> Some setups use "server-name", some others "next-server".  I even
> saw "option tftp-server-name" sometimes.  Most of the time they
> all have the same value.
> 
> I think that "server-name" is just a string identifying the DHCP
> server, though I don't really understand the purpose of such an option.
> The "next-server" option seems to describe the IP address (or
> FQDN) or the TFTP server.
> 
> Am I right ?  In this case, what's the usefulness of
> "option tftp-server-name" ?
> 
> I would be glad of someone could point out the reference or a
> description for this.

I think I succeeded to gather enough informations about this to
reply myself, for the record.

* "server-name" is just an informative name, giving the real name
  of the DHCP server.

* "next-server" is the ``address of the server to use in the next step
  of the client's bootstrap process''.  No protocol is specified and
  hence I assume this is implementation-defined.

* "tfp-server-name" is just an informative name as well, when the
  "sname" (server-name) field has been used for DHCP options.

Am I right ?

The use of TFTP protocol is coerced by the PXE specification to
fetch the very first program that will be run on the client.
Then it is up to this first program to do what it want.  For instance,
on NetBSD a "loader" is fetched via TFTP and then the latter will
in turn fetch the kernel using NFS.  It is explicitely stated that:
``the client will assume that this next-server handles both tftp
and nfs.''

Hope this will help.
Best regards,
-- 
Jeremie Le Hen
< jeremie at le-hen dot org >< ttz at chchile dot org >