Re: [Etherboot-developers] DHCP option 175

[Michael B. <mb...@fe...>]

On Wed, 22 May 2002, Christoph Plattner wrote:
> In my opinion, ASCII text is always preferred. For DHCPD maintainence
> binary data is not a good idea ! And the byte space is definitive not
> critical in this point (3 or 8 bytes ....)

I have a slight preference for ASCII text, but it's not really a big
issue: you can just use some of the functions listed in dhcp-eval(5) to
generate the ASCII equivalent from the binary data.

> But is the whole stuff really a good idea ?
> Is it important to know the interface on the client side ?

Yes, if it affects the kernel+initrd that the client should use.

> Normally an admin should know the components, ...
> On the other hand, PCs are quickly exchanged ...

IMO, anything that decreases maintenance requirements from O(n) or above
down to O(1) is a good thing.

> But should the loaded image not independent of the NIC ?
> A Linux kenrel for example should have all needed NIC
> drivers compiled in.

Most distributions ship with modularized kernels.  Since it's possible to
use these kernels to boot diskless terminals via Etherboot (with an
appropriate initrd), why should we force users to recompile their kernel?

> Using PCI ID is perhaps not the best idea ! Perhaps it is a
> better idea to give "keywords" at boot ROM compile time,
> which is passed as tag 175.
> Example:
> I have a new PC with onboard 3COM another with onboard i82559
> and one with a classic rtl8139 NIC inserted. Then I have to
> build the 3 boot ROMs, like
> make bin32/3c900.rom KEY175="NEWPC_TYPE_1"
> make bin32/eepro100.rom KEY175="NEWPC_TYPE_2"
> make bin32/rtl8139.rom KEY175="OLDPC_TYPE_1"

This is more than O(1); it requires the administrator to manually maintain
parts of dhcpd.conf that could be handled completely automatically.  Using
the PCI IDs means that an administrator need never touch or even look at
the Etherboot-specific parts of dhcpd.conf.


I think this scheme could work well alongside the send-the-PCI-ID scheme.
Etherboot can always send the PCI ID and for most cases this is all that
will be needed.  The dhcpd server can be configured such that Etherboot
clients will work instantly without any manual changes required by the
administrator.  For the few cases when the PCI ID is insufficient to
determine the card configuration, an additional (vendor-encapsulated)
option can be used to pass an arbitrary keyword defined at build time in
the way you describe.

Michael