Wake-on-LAN
Wake-on-LAN (WoL) is a feature to switch on a computer via the network.
Hardware settings
The target computer's motherboard and Network Interface Controller have to support Wake-on-LAN. The target computer has to be physically connected (with a cable) to a router or to the source computer for WoL to work properly. Some wireless cards have support for Wake on Wireless (WoWLAN or WoW).
The Wake-on-LAN feature also has to be enabled in the computer's BIOS. Different motherboard manufacturers use slightly different language for this feature. Look for terminology such as "PCI Power up", "Allow PCI wake up event" or "Boot from PCI/PCI-E".
Note that some motherboards are affected by a bug that can cause immediate or random #Wake-up after shutdown whenever the BIOS WoL feature is enabled.
Software configuration
Enable WoL on the network adapter
Depending on the hardware, the network driver may have WoL switched off by default.
To query this status or to change the settings, install ethtool, determine the name of the network interface, and query it using the command:
# ethtool ''interface'' | grep Wake-on
Supports Wake-on: pumbag Wake-on: d
The Wake-on values define what activity triggers wake up: d (disabled), p (PHY activity), u (unicast activity), m (multicast activity), b (broadcast activity), (ARP activity), and g (magic packet activity). The value g is required for WoL to work, if not, the following command enables the WoL feature in the driver:
# ethtool -s interface wol g
This command might not last beyond the next reboot and in this case must be repeated via some mechanism. Common solutions are listed in the following subsections.
systemd.link
Link-level configuration is possible through systemd-networkd#link files. The actual setup is performed by the udev builtin. Add the option to the network link file:
/etc/systemd/network/50-wired.link
[Match] MACAddress=''aa:bb:cc:dd:ee:ff'' [Link] NamePolicy=kernel database onboard slot path MACAddressPolicy=persistent '''WakeOnLan=magic'''
Also see for more information.
- Only the first matching file is is applied. The content of the default link file
/usr/lib/systemd/network/99-default.linkshipped with systemd has to be included, otherwise the interface might be misconfigured. - To be considered, the file name should alphabetically come before the default
99-default.link. For example50-wired.linkworks. - This configuration applies only to the link-level, and is independent of network-level daemons such as NetworkManager or systemd-networkd.
- In the
Matchsection,OriginalName=can also be used to identify the interface.
systemd service
This is an equivalent of previous option, but uses a standalone systemd service.
Alternatively install the package, then activate this new service by starting .
udev
udev is capable of running any command as soon as a device is visible. The following rule will turn on WOL on all network interfaces whose name matches . The file name is important and must start with a number between 81 and 99 so that it runs after , which renames interfaces with predictable names. Otherwise, would be undefined and the rule would not run.
The $name placeholder will be replaced by the value of the variable for the matched device.
cron
A command can be run each time the computer is (re)booted using "@reboot" in a crontab. First, make sure cron is enabled, and then edit a crontab for the root user that contains the following line:
@reboot /usr/bin/ethtool -s interface wol g
netctl
If using netctl, one can make this setting persistent by adding the following the netctl profile:
/etc/netctl/''profile''
ExecUpPost='/usr/bin/ethtool -s ''interface'' wol g'
NetworkManager
NetworkManager provides Wake-on-LAN ethernet support. One way to enable Wake-on-LAN by magic packet is through nmcli.
First, search for the name of the wired connection:
By following, one can view current status of Wake-on-LAN settings:
Enable Wake-on-LAN by magic packet on that connection:
# nmcli c modify "wired1" 802-3-ethernet.wake-on-lan magic
Then reboot, possibly two times. To disable Wake-on-Lan, substitute with .
The Wake-on-LAN settings can also be changed from the GUI using .
You can disable Wake-on-Lan for all connections permanently by adding a dedicated configuration file :
Enable WoL in TLP
When using TLP for suspend/hibernate, the setting should be set to in /etc/tlp.conf to allow resuming the computer with WoL.
Trigger a wake up
To trigger WoL on a target machine, its MAC address must be known. To obtain it, execute the following command from the machine:
Here the MAC address is .
In its simplest form, Wake-on-LAN broadcasts the magic packet as an ethernet frame, containing the MAC address within the current network subnet, below the IP protocol layer. The knowledge of an IP address for the target computer is not necessary, as it operates on layer 2 (Data Link).
If used to wake up a computer over the internet or in a different subnet, it typically relies on the router to relay the packet and broadcast it. In this scenario, the external IP address of the router must be known. Keep in mind that most routers by default will not relay subnet directed broadcasts as a safety precaution and need to be explicitly told to do so.
Applications that are able to send magic packets for Wake-on-LAN:
- gWakeOnLAN — GTK utility to awake turned off computers through the Wake-on-LAN feature.
On the same LAN
If you are connected directly to another computer through a network cable, or the traffic within a LAN is not firewalled, then using Wake-on-LAN should be straightforward since there is no need to worry about port redirects.
In the simplest case the default broadcast address is used:
$ wol target_MAC_address
To broadcast the magic packet only to a specific subnet or host, use the switch:
$ wol -i target_IP target_MAC_address
Across the internet
When the source and target computers are separated by a NAT router, different solution can be envisaged:
- If the router supports WoL, one can rely on it to properly broadcast the packet into the local network.
Otherwise Wake-on-Lan can be achieved via port forwarding. The router needs to be configured using one of these two options:
- Forward a different port to each target machine. This requires any target machine to have a static IP address on its LAN.
- Forward a single port to the broadcast address. Most routers do not allow to forward to broadcast, however if you can get shell access to your router, through telnet, ssh, serial cable or other mean, run the command: This example assumes the network is 192.168.1.0/24 and uses net0 as network interface. Now, forward UDP port 9 to 192.168.1.254. This solution was successfully tested on a Linksys WRT54G running Tomato, and on the Verizon FIOS ActionTec router. For notes on how to do it on a router with DD-WRT firmware, see this tutorial and for a router with OpenWrt firmware, see this tutorial.
In any case, run the following command from the source computer to trigger wake-up:
$ wol -p forwarded_port -i router_IP target_MAC_address
Miscellaneous
Check reception of the magic packets
In order to make sure the WoL packets reach the target computer, one can listen to the UDP port, usually port 9, for magic packets. The magic packet frame expected contains 6 bytes of FF followed by 16 repetitions of the target computer's MAC (6 bytes each) for a total of 102 bytes.
Using netcat
This can be performed by installing on the target computer and using the following command:
# nc --udp --listen --local-port=9 --hexdump
Then wait for the incoming traffic to appear in the terminal.
Using ngrep
Install on the target computer and type the following command:
# ngrep '\xff{6}(.{6})\1{15}' -x port 9
Example of WoL script
Here is a script that illustrates the use of with different machines:
Troubleshooting
Network adapter is still powered off on shutdown
Setting auto negotiation to may help if WOL is configured through nmcli and network adapter is still powered off on shutdown.
Set it using:
# nmcli c modify "wired1" 802-3-ethernet.auto-negotiate yes
Wake-up after shutdown
It is known that some motherboards are affected by a bug that can cause immediate or random wake-up after a shutdown whenever the BIOS WoL feature is enabled (as discussed in this thread for example).
Fix using BIOS Settings
The following actions in the BIOS preferences can solve this issue with some motherboards:
- Disable all references to xHCI in the USB settings (note this will also disable USB 3.0 at boot time)
- Disable EuP 2013 if it is explicitly an option
- Optionally enable wake-up on keyboard actions
Fix by Kernel quirks
The issue can also be solved by adding the following kernel boot parameter: This activates the following quirks:
Battery draining problem
Some laptops have a battery draining problem after shutdown . This might be caused by enabled WOL. To solve this problem, disable it by using ethtool as mentioned above.
# ethtool -s net0 wol d
Realtek
Users with Realtek 8168 8169 8101 8111(C) based NICs (cards / and on-board) may notice a problem where the NIC seems to be disabled on boot and has no Link light. See Network configuration/Ethernet#Realtek no link / WOL problem.
If the link light on the network switch is enabled when the computer is turned off but wake on LAN is still not working, booting the system using the r8168 kernel module at least once and then switching back to the r8169 kernel module included with the kernel seems to fix it at least in the following configurations:
- MSI B85M-E45 motherboard, BIOS version V10.9, onboard Realtek 8111G chipset
For the module you might need to set the s5wol=1 module option to enable the wake on LAN functionality.
alx driver support
For some newer Atheros-based NICs (such as Atheros AR8161 and Killer E2500), WOL support has been disabled in the mainline module due to a bug causing unintentional wake-up (see this patch discussion). A patch can be applied (or installed as a dkms module using the package) which both restores WOL support and fixes the underlying bug, as outlined in this thread.