* 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.