[HOWTO] SGI tftp boot with ARCLoad

[Julien BLACHE <jblache@debian.org>]

Hi,

As promised last month, here's a quick howto on how to tftp boot an
SGI machine using ARCLoad.

This should be usable to load d-i using ARCLoad instead of the current
tip22/tip32 images. That way, the tip22/tip32 images would no longer
be needed, which would help the d-i build and simplify things if, for
some reason, you need to use a modified initrd.

I haven't tested booting d-i; if somebody (tbm ?) can provide a d-i
kernel and initrd for r4k-ip22, I'll happily test that.

So, here's how it works.


On the tftp server:
-------------------

 - arc.cf: the arcload config file
 - arcload.ecoff: ARCLoad itself, here for 32bit PROM, use arcload64
   otherwise.
 - vmlinux-2.6.24-1-r4k-ip22: 2.6.24 kernel


Arcload config (arc.cf):
------------------------

append "root=/dev/sda3";
append "ro";
append "console=ttyS0";

ip22 {
        2624 {
                description "Debian GNU/Linux Sid 2.6.24";
                image "bootp():/vmlinux-2.6.24-1-r4k-ip22";
        }

        single {
                description "Single-user debug mode";
                append "single";
        }
}

(this is a minimal config file; with the d-i initrd, obviously you
want to change root= to something else)


Booting:
--------

Set the following PROM variables:

>> setenv OSLoadFilename ip22(2624)

Name of the option to boot. IP22 machine, 2624 option. Options can be
combined, like ip22(2624,single).

ARCLoad can also detect the machine type itself (see the ARCLoad
doc[1] for details, and the sample config files shipped in the
package, notably the CD config example).

>> setenv OSLoadPartition bootp():

This tells ARCLoad to load its config from the tftp server.

Now, run ARCLoad itself, and watch the machine boot:

>> bootp():/arcload.ecoff



This needs to be tested with a d-i kernel and initrd; it should work
but there's still the possibility that the initrd couldn't be loaded
properly in memory like we experienced with tip22 recently.

To add an initrd to the mix, add
  initrd "bootp():/initrd-bla-bla-bla"
in the 2624 section in the config used above.

The arcload package ships a sample config for CD booting; this too
could help d-i. The CD boot sample is a good example of using ARCLoad
platform detection capabilities.


If anybody's interested in going further with arcload, I'll provide
all the needed support.

JB.

[1] <http://www.linux-mips.org/wiki/ARCLoad>

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 Julien BLACHE <jblache@debian.org>  |  Debian, because code matters more 
 Debian & GNU/Linux Developer        |       <http://www.debian.org>
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