WOL: how does it work?

Claude Pignol cpignol at seismiccity.com
Fri Sep 7 14:23:27 PDT 2001

I think the wake up depends on how the node enter the  sleeping state.
May be you could try this with the original kernel of Beowulf 27bz-7
power down remotely a node:
bpctl -S Node_Number -s pwroff

The node shutdown and the power off but the NIC is alive
Don't remove the power plug. (Important)

send the magic packet

ether-wake -i eth4 00:E0:81:03:21:DD

It should wake up the node
If not add the kernel parameter
to the slave node kernel

And restart the whole process.

This works fine for me (but It's not the same motherboard)
I hope this could help


Martin Siegert wrote:

>I am trying to get wake-on-lan (WOL) to wirk on my Beowulf cluster
>and until now I failed. Admittedly I don't know much about WOL, thus
>this failure may just be due to some stupid mistake on my part.
>Here is the problem: Each node draws a current of about 1.5A (I measured
>that a few days ago). Since I have about 70 of those, booting all nodes
>at once will draw all of the sudden a current of more than 100A. The
>people who run our machine room don't allow me to do that (probably for
>good reason). Thus I decided on the following approach:
>The bios for the motherboard that I'm using (Tyan Thunder K7) allows
>two setting for what to do after a power failure when the power comes
>back on: a) stay off or b) power on.
>Instead of choosing b) for all nodes (wich would cause the aforementioned
>problem)  I want to choose b) only for the master node and a) for all slaves.
>Then use WOL from the master node to wake up the slave sequentially
>using a script and the ether-wake program from
>Unfortunately, I have been unable to wake up a node. Here is what I do:
>"halt" a node. Detach the power cable. Reattach the power cable.
>At this point the lights on the two onboard NICs (the Tyan web site
>and the printing on the chips say that those are 3c920, the 3c59x driver
>identifies them as 3c980; I don't know whether that is relevant; the NICs
>work fine) come on. A Tyan technician told me that WOL on the Thunder K7 is
>always on, no special BIOS setup would be needed. They also told me that I
>have to use a 2.4.x kernel because only those would support APCI. I don't
>understand why the kernel is important here: when the node is halted
>what difference does the kernel make for the receiving of the magic WOL
>packet that is supposed to wake up the box? Anyway, I compiled a
>2.4.9-ac8 kernel with APIC enabled, which I use with the "noapic"
>kernel option in /etc/lilo.conf. I have also tried the stock RH 7.1
>2.4.3-12smp kernel without any difference with respect to WOL (i.e.,
>no success).
>After reattaching the power cable I then send the magic packet from
>the master node:
>./ether-wake -i eth4 00:E0:81:03:21:DD
>where 00:E0:81:03:21:DD is the MAC address of one of the onboard NICs
>on the node. tcpdump shows that the packet actually is sent. Also the
>lights in the NICs on the sending and receiving end flash, but otherwise
>nothing happens.
>What's wrong? Any suggestions are most appreciated.
>Martin Siegert
>Academic Computing Services                        phone: (604) 291-4691
>Simon Fraser University                            fax:   (604) 291-4242
>Burnaby, British Columbia                          email: siegert at sfu.ca
>Canada  V5A 1S6
>Beowulf mailing list, Beowulf at beowulf.org
>To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf

Claude Pignol SeismicCity, Inc. <http://www.seismiccity.com>
2900 Wilcrest Dr.    Suite 470  Houston TX 77042
Phone:832 251 1471 Mob:281 703 2933  Fax:832 251 0586

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