HowTo: Enable Wake-on-LAN on Gentoo

Wake-on-LAN also know as WOL is the ability to switch on a computer that is connected to a network (local or not) by means of a special network message called a magic packet. This magic packet contains the MAC address of the destination computer. If the destination computer has a network interface card that support WOL then the system wakes up.

In this post I'll describe how to setup a Gentoo destination computer so that it can be turned on from another computer.

For sake of simplicity I've broken down the procedure into a few steps:
1) Enable WOL in BIOS
2) Install ethtool
3) Collect network interface information
4) Enable WOL for the next shutdown
5) Make WOL always enabled
6) Wake up the computer from local network
7) Wake up the computer from internet
8) Troubleshooting

1) Enable WOL in BIOS

These days pretty much all integrated or otherwise NICs support Wake-on-LAN, however more often than not you'll need to enable it in the BIOS. There are literally hundreds of BIOS around but look for the typical options: "Enable Wake-on-LAN", "Enable Wake on PCI" and "Enable Power of PCIE Devices".

2) Install ethtool

Take emerge for a spin and install sys-apps/ethtool. ethtool is an utility for examining and tuning ethernet-based network interfaces.

1. # emerge ethtool
2. # rehash

3) Collect network interface information

To use Wake-on-LAN we need to identify the NIC MAC address. For example, in my computer the MAC address is 00:aa:11:bb:22:cc.

1. # ifconfigeth0      Link encap:Ethernet  HWaddr 00:aa:11:bb:22:cc 
          inet addr:192.168.1.3  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fa10::120:1aef:ffeb:b78a/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:129199 errors:0 dropped:0 overruns:0 frame:0
          TX packets:165680 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:58680158 (55.9 MiB)  TX bytes:26252276 (25.0 MiB)
          Interrupt:10 Base address:0xa000

lo        Link encap:Local Loopback 
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

Check if the NIC does support the Wake-on-LAN feature:

1. # ethtool eth0Settings for eth0:
Supported ports: [ MII ]
Supported link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
Supported pause frame use: No
Supports auto-negotiation: Yes
Advertised link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
Advertised pause frame use: No
Advertised auto-negotiation: Yes
Speed: 100Mb/s
Duplex: Full
Port: MII
PHYAD: 1
Transceiver: external
Auto-negotiation: on
Supports Wake-on: g
Wake-on: d
Link detected: yes

The "Supports Wake-on: g" string means that the NIC does in fact support Wake-on-LAN while "Wake-on: d" is a sign that the feature isn't active.

4) Enable WOL for the next shutdown

To command the operating system to enable WOL for the eth0 network interface run:

1. # ethtool -s eth0 wol g

Issuing ethtool again now returns "Wake-on: g" so now we have WOL enabled:

1. # ethtool eth0
Settings for eth0:
Supported ports: [ MII ]
Supported link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
Supported pause frame use: No
Supports auto-negotiation: Yes
Advertised link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
Advertised pause frame use: No
Advertised auto-negotiation: Yes
Speed: 100Mb/s
Duplex: Full
Port: MII
PHYAD: 1
Transceiver: external
Auto-negotiation: on
Supports Wake-on: g
Wake-on: g
Link detected: yes

5) Make WOL always enabled

To have WOL always enabled Gentoo needs to be told that eth0 WOL is supposed to be active.

Assuming your're using OpenRC (which you should) add ethtool -s eth0 wol g to /etc/local.d/wol.start:

1. # echo "ethtool -s eth0 wol g" > /etc/local.d/wol.start
2. # chmod +x /etc/local.d/wol.start

The /etc/local.d/ directory contains scripts which are to be run when local service is started or stopped, so by adding a script with an executable script with a .start extension, it will be run when the local service is started at boot.

6) Wake up the computer from local network

From the computer that will be used to send the magic WOL packet, install and run net-misc/wakeonlan:

1. # emerge wakeonlan
2. # rehash
3. # wakeonlan -i 192.168.1.255 00:50:8d:eb:a7:8a

Replace 192.168.1.255 with the broadcast from your network. 192.168.1.255 is the broadcast address for a 192.168.1.x subnet which is the case of my local network.

7) Wake up the computer from internet

This involves enabling port forwarding of UDP port 9 to the destination computer in the router's administration webpage. To fully benefit from WOL you should configure a dynamic DNS service.

Afterwards to issue the wake up command you can use websites such as http://wakeonlan.me, Android applications (Wake on Lan) or any other Wake-on-LAN application (every Unix-like system as an alternative available). Just make sure to use your dynamic DNS provided address and the destination computer's MAC.

8) Troubleshooting

While troubleshooting Wake-on-LAN I've noticed that if you use GRUB without timeout set and poweroff the computer while on the operating system selection menu, the next time you try to use Wake-on-LAN it won't work. So make sure you have GRUB with a timeout set (which is the case will all default installation of GRUB).

If the computer is disconnected from the power supply you'll need to boot the computer and turn off again so that the NIC assumes the WOL definitions.