[syslinux] Re: Q: passing DHCP options to the booted linux-kernel?

[Ph. Marek]

> > That would be perfect, especially, if the kernel understood this value
> > too :-)
>
> Why should the kernel care about it?
At least in 2.4.x the option "kernel IP autoconfiguration" uses the "ip=" 
parameter, which specifies the ip- and gateway-address, netmask and 
dhcp-server.
This configuration will be valid ONLY on the network interface which got this 
information; therefore, only this interface can be configured.
So there needs to be a way to tell the kernel about that.

> > Thanks a lot, I'll be hoping for that.
> > If you've got a patch for something around 2.4.20 I'm ready to test.
> > (I'll need a newer pxelinux too, I suppose).
>
> The ipconfig/nfsroot stuff in the kernel is going away for 2.5, so I'm
> not particularly interested in hacking on it since it's a dead end
> anyway.  It's all moving to userspace in 2.5, and you can do it in
> userspace in 2.4 as well by using an initrd and pivot_root.
I know. I currently use a self-written program which checks the line-status of 
the interfaces (via MII-registers), and if only 1 cable is plugged into the 
cards, this card is configured.

My fear is mostly that using userspace for a lot of things tends to need more 
and more libraries, which I have to present on a boot floppy for 
not-PXE-enabled machines - there space is very valuable.
And no, I can't use NFSroot- I have to use some network drivers which can't be 
compiled into the kernel but are modules, so I need userspace to load them.

So in the long term you're right - just passing an argument specifying the 
hardware address from pxelinux to the kernel should be sufficient for most 
cases (except when two cards share the hardware address *). As 2.5 will get a 
klibc (although I have to admit that I don't really know what that means - is 
that a minimal substitute for libc?) I hope that my needed userspace 
libraries set will get smaller.


Regards

Phil


*) No, it's not a 1/2^48 chance. I know some machines which record a UAA 
across reboots, and if these are set for ease of network management ... 
conflicts happen.