I have never used Wake-On-Lan feature before. This is my first time to try remotely waking up a Linux computer.

In the remote computer, I did the following:
1. enable WOL in BIOS
2. execute 'ethtool -s eth0 wol g' to enable WOL in NIC
3. Now the response of 'ethtool eth0' is
In the local computer, I did the following:
1. ssh <remote_computer>
2. shutdown -h now
when the remote computer was shutdown. I perform
3. I sent magic packet with 'wakeonlan -i 192.168.0.255 <MAC>'
the remote computer is powered up. This is great.

However, if I 'ssh' to and 'shutdown -h now' the remote computer, and on the remote side I plugged out the power supply socket (fully power down) for a few minutes and plug in the power supply socket again, I could see the LED in NIC was lit up. At this situation, I could never wake up remotely. In other words, the plug out power socket will disable the WOL feature. I experiment many times, the situation is repeated.

I don't know if this is a correct result. I would appreciate if someone could answer me.

There's a known problem with WOL.
The kernel developers are "working on it".
See this other (recent) thread: http://www.linuxquestions.org/questi...-issue-678917/

Yes, this is a correct result.

Whenever you enable wake-on-LAN (WOL) with ethtool, the NIC responds by setting up its registers to make ready for entering a low power state (PCI D3 state) on shutdown, sleep, or hibernation. Power to the NIC is supplied by the PCI or PCIe bus, and even when you power off your computer, at least one voltage source, called Vaux, is left active. (Depending upon your particular system, you may also have a second voltage source active, called Vcc.) This is the power source the NIC uses to stay alive when your computer is shut down.

However, when you unplug your computer -- or open the rocker switch (if you have one) on the exterior of your power supply -- you remove *all* PCI power, including Vaux, causing the NIC to lose those register settings and revert to default values on power up.

Of course, WOL is dependent upon the kernel's correctness in handling PCI power management, and upon your NIC driver's correctness in setting up the registers and preparing for transition to the PCI D3 power state. From time to time, one or both get broken, but *usually* not in a stable release kernel.

@jcliburn:

Thanks for the update and detailed information.

WoL is currently broken on my LAN (Target to WoL = kernel 2.6.15-52-386, "kubuntu"), but I expect the clever people will get it fixed soon.

Meanwhile, I wish I knew how to power down that PC, and still be able to wake it up later without having to climb 3 flights of stairs and press the little button. WoL would be perfect.

It isn't that important, but I wish it worked.