HOW-TO:Set up Wake-on-LAN for Ubuntu

Before you start

First off, the motherboard should support the WOL (Wake On LAN) and it should be enabled in the BIOS. Different BIOS/motherboard do it differently; on ASUS (P5N7A-VM), it's under Power > APM Configuration and in there "Resume On PCIE Wake" and "Resume On LAN(MAC)" should be enabled.

Enable WOL in the OS

Even though WOL works in network layer 2, OS support is still one of the important things to make it work. Even if you see the light on the Ethernet port is on after the halt/shutdown, the OS shuts off the Ethernet internally. One must tell Ethernet controller to WOL when boots up and tell "halt" script not to bring down controller during shut-down.