[syslinux] pxelinux search order for configuration file
Schlomo Schapiro
schlomo at schapiro.org
Sun Feb 5 06:59:30 PST 2012
Hi,
On 5 February 2012 15:44, Christoph Hanle <christoph.hanle at leinpfad.de>wrote:
> Hi Everyone.
> is there a need to have on searching the configuration file the request
> for the "odd ip addresses" ?
> Let me explain:
> from /doc/pxelinux.txt :
> ...
> Next, it will search for the config file using its own IP address
> in upper case hexadecimal, e.g. 192.0.2.91 -> C000025B
> (you can use the included progam "gethostip" to compute the
> hexadecimal IP address for any host.)
>
> If that file is not found, it will remove one hex digit and try
> again. Ultimately, it will try looking for a file named "default"
> (in lower case).
>
> As an example, if the boot file name is /mybootdir/pxelinux.0, the
> UUID is b8945908-d6a6-41a9-611d-**74a6ab80b83d, the Ethernet MAC
> address is 88:99:AA:BB:CC:DD and the IP address 192.0.2.91, it will
> try:
>
> /mybootdir/pxelinux.cfg/**b8945908-d6a6-41a9-611d-**74a6ab80b83d
> /mybootdir/pxelinux.cfg/01-88-**99-aa-bb-cc-dd
> /mybootdir/pxelinux.cfg/**C000025B
> /mybootdir/pxelinux.cfg/**C000025
> /mybootdir/pxelinux.cfg/C00002
> /mybootdir/pxelinux.cfg/C0000
> /mybootdir/pxelinux.cfg/C000
> /mybootdir/pxelinux.cfg/C00
> /mybootdir/pxelinux.cfg/C0
> /mybootdir/pxelinux.cfg/C
> /mybootdir/pxelinux.cfg/**default
> ...
> Why is there the need, or is there any practical usage to request for:
> C000025, C0000, C00 an C ?
>
AFAIKT the idea is to have different boot configurations for different
subnets. Indeed, C, C0 etc. might be a bit extreme.
My personal solution to this problem is to always return a valid boot
configuration to the first request (the one with the UUID). If you do HTTP
booting then this is much easier to achieve as you can have a simple CGI or
PHP script determine what to do. With TFTP booting you need a TFTP server
with dynamic content generation. I once found one and decided that this
won't work as well as via HTTP.
Regards,
Schlomo
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