Re: Info : Using a PowerMac G5 as a server

Surprisingly, the Linux kernel does a very good job on this machine in
terms of hardware support and stability : everything works perfectly.
But the global OS fails pathetically in the two said points.
Here are my findings so far, I hope it will help people in the same situation :

1/ Booting a PowerMac G5 headless

This hasn't so much to do with Linux per se, but rather with Yaboot
which seems to be the de-facto standard bootloader on the OpenFirmware
platform.
For some reason, at some point in the booting process, yaboot relies
on a screen being present. If no screen is attached, it will hang. So
much for headless booting.
Now I've figured out several workarounds :
 -> Fake a screen by plugging in a resistor into your VGA port (or to
your DVI port using an adapter). This sure works, but it's rather
redneck
 -> For some reason, the part of yaboot that actually depends on the
script is the "ofboot.b" forth script. This scripts' purpose is to
give you an option of booting off of a CD. I really don't get it since
OpenFirmware itself lets you boot off of a CD just by pressing "C" on
boot. So basically if you skip ofboot.b, you're good to go. When
installing yaboot with ybin, ybin sets the "boot-device" variable in
OpenFirmware to point to ofboot.b. So if you point boot-device
straight to the yaboo binary, you should be able to boot headless
without any issue. Here are several ways to do it :

You may want to Tony Breeds. I'm not sure what happen when ofboot.b
tries to "fixup" the input/output devices, but we could certainly make
it easier for ofboot.b to be optional.

       - Go to the OpenFirmware prompt (Command-Option-O-F on boot),
and type "setenv boot-device=hd:2,yaboot" (modify the hd:2
accordingly), then "boot"
       - You might be able to achieve the same effect using the
"nvram" tool straight from linux
       - I think simply removing the "magicboot" line off of
yaboot.conf might fix it as well

IOW, it _is_ possible to boot a PowerMac G5 headless on Linux without
any hardware modification.

Yeah but I think OF gets into all kind of funny state if you try to open
the graphics device with nothing connected, and that's an OF bug, it
shouldn't happen.

2/ Rebooting automagically after a power failure

Now this is less fun : I still don't have any solution to offer. To
understand the situation, you should know that this has to be set in
the power-management chip.
Previous PowerMacs used a "PMU" chip, which was fully supported. All
you had to do was to echo "server_mode=1" to /proc/pmu/options.

Thing is, G5's use a new chip, named "SMU". And AFAIK, there's no such
option for those machines…

Yes, there is. We reverse engineered that a while back and somebody even
wrote a little tool to control it, though I don't remember where that
can be found... If necessary, we can try to dig again, the RE wasn't
that hard.

Cheers,
Ben.

So if anyone ever knows any element of answer on this, I'd be really
interested !

Kind regards,

 - Romain
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