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Re: Wake-on-LAN



* Timothy Murphy <gayleard eircom net> [20090405 22:46]:
> Roberto Ragusa wrote:
> 
> Thanks very much.
> 
> > Wake On LAN should actually be able to wake a system up
> > from power off state, so it should reasonably work
> > for suspended systems too.
> > 
> > As a first thing, the NIC LED (or the LED on the ethernet switch)
> > should be on; it will be on even when the system is switched off,
> > if WOL is active.
> 
> Surprisingly, it is on when I "shutdown -h" the machine,
> but off when I set the machine to hibernate.

That's because the drivers deal with ACPI states S3 and S4 different
to S5.

You *can* wake the system up from S3/S4, but you need to issue a
command first.

# echo -n LAN > /proc/acpi/wakeup

Once you have done this, then you can suspend/hibernate and WOL the
system. The patch for this should be in CentOS 5.3.

Also, different drivers may behave differently in this respect. I only
know of e1000/e1000e behaving correctly with this as I've not tested
it on other hardware.

> > Then WOL has to be enabled. You can trust the BIOS
> > or, better, run
> > 
> >   ethtool eth0
> > 
> > and you will get something like
> > 
> >   Supports Wake-on: pumbag
> >   Wake-on: g
> 
> I had forgotten about ethtool.
> I do indeed get "Wake-on: g"
> which I see means "Wake on MagicPacket".
> 
> So I must see if and hopefully how
> I can send the machine a "MagicPacket".

ether-wake <MAC> is what I used when I did all the testing on
this. It's a tool that generates the exact packet needed.

-- 
Anders Rayner-Karlsson <anders trudheim co uk>
All-Round Linux Tinkerer, RHCE and PITA DeLuxe


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