[syslinux] ISOLinux, menu.c32 and PXE handoff?

[Sergey Vlasov]

On Tue, Jul 22, 2008 at 07:08:12PM +0400, Sergey Vlasov wrote:
> -----------------------------------------------------------------------
> #!gpxe
> set filename tftp://10.0.0.1/boot/pxelinux.0
> kernel tftp://10.0.0.1/boot/pxelinux.0
> boot
> -----------------------------------------------------------------------
[...]
> This would work if the problematic DHCP server does not send the
> boot filename at all.  If the server sends the boot filename, that
> filename would still be used instead of the name specified in the
> script - in this case you can try
> 
> set net0.dhcp/filename tftp://10.0.0.1/boot/pxelinux.0
> 
> The above command will override the filename in the DHCP response,
> but it would work only for booting from the first network card -
> boot attempts from subsequent interfaces will fail.

There is yet another way to handle a DHCP server sending the boot
filename, which does not break with multiple network cards - you can
set a PXELINUX-specific DHCP option:

-----------------------------------------------------------------------
#!gpxe
set 210:string tftp://10.0.0.1/boot/
kernel tftp://10.0.0.1/boot/pxelinux.0
boot
-----------------------------------------------------------------------

Option 210 is "Path Prefix Option", described in RFC 5071
(doc/rfc5071.txt in syslinux sources).  This option overrides the
guessing of prefix from boot filename in pxelinux.

This gpxe script will also work only if the DHCP server does not
send the option 210 itself (if it does, the only solution is to set
net0.dhcp/210:string instead, which hardcodes the net0 interface).
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