Re: specifiying a preseed url by dhcp
On Tue, Nov 30, 2004 at 03:12:04AM -0500, Joey Hess wrote:
The message is indeed fiveteen months old.
> 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
> dhcp.
>
> 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
> file.
>
> 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
Meanwhile we have `netcfg` identifing itself during DHCP-request
and `network-preseed` getting the preseed/url from the DHCP-lease.
Together they solve the above described problem,
they make DHCP preseeding possible.
Cheers
Geert Stappers
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