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specifiying a preseed url by dhcp

Since it looks like hppa automated installs cannot be done with a
preseed url in the kernel boot parameters, due to size restrictions, I
took at look at ways to deliver the information about preseeding via

First, how kickstart does it: I was under the impression before that
kickstart allowed specifying the kickstart file to use in the dhcp
configuation, and that this would work with PXE booting. Well, sort of.
Kickstart will look at the dhcp next-server and filename fields in the
dhcp response, and try to use something like next-server:/filename
(nfs) as the kickstart file. However, I don't see how this can be used
for PXE booting, since we need filename there to point to the file to
boot, and if next-server is set, it is used as the tftp server. The
filename field is also used when netbooting sparc, hppa, etc. So
overloading it to be used for preseeding doesn't seem good. In fact all
the kickstart pxe boot setups I've found specify the kickstart file via
a ks= kernel boot option to avoid this.

Next I looked at the dhcp rfcs. The dhcp options seemed like the obvious
way to get an url passed from dhcp to d-i. I looked at using option 43,
the vendor defined option, since its use is quite close to how d-i would
work. However, at least the debian dhcp package does not allow option-43
in dhcpd.conf.

We could pick an option in the 128-254 range and use it, but we might be
violating rfc2939 by doing so, since it requires that these "MUST NOT be
defined for use by any publicly distributed DHCP server, client or relay
agent implementations". I'm not sure how much wiggle room there is in
"client" -- it's not like d-i's dhcp client would know about the option,
though d-i would, and we'd have to put something like "request option-nnn" in
dhclient.conf. There's always the potential that whatever private use
option number we choose will be used at some installation site for
something else.

We could add a boot option to make d-i look at a particular dhcp option
for preseeding, and leave it up to the admin. preseed/dhcp_opt=128. This
might still run out of kernel command line space on hppa (it's very
small) and it's a lot of layers of indirection to get to the preseed

We could go through the process to get an option numer assigned by iana.
I don't have the time or the patience, but if someone does this is
probably the best way.

see shy jo

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