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Wake-on-LAN

Wake-on-LAN switches a computer on over the network. Another computer on the same network sends a short message, a “magic packet”, to the network card of the switched-off machine, and the machine starts as if you had pressed its power button.

bromigOS keeps Wake-on-LAN on for wired network cards, by itself. You don’t need to run anything. It stays on across restarts, after an update, and when you plug the cable into another port.

BRODEC’s Power on button on your phone uses it: it asks your lab, or another of your machines on the same network, to send the packet for you.

What it needs

  • An Ethernet cable. Wi-Fi can’t wake a powered-off desktop: the Wi-Fi card is off with the rest of the machine. Connect a cable from the machine’s network port to your router or switch.

  • A network card that supports it. Almost every desktop’s built-in network port does.

  • The setting in the BIOS (UEFI). bromigOS can’t change it for you. Start the machine and press Delete or F2 while it starts, then:

    BoardWhere the setting is
    ASUSAdvanced → APM Configuration → Power On By PCI-E: Enabled, and ErP Ready: Disabled
    MSISettings → Advanced → Wake Up Event Setup → Resume By PCI-E Device: Enabled, and Power Management Setup → ErP Ready: Disabled
    GigabyteSettings → Platform Power → Wake on LAN: Enabled, and ErP: Disabled
    ASRockAdvanced → ACPI Configuration → PCIE Devices Power On: Enabled, and Deep Sleep: Disabled
    DellPower Management → Wake on LAN/WLAN: LAN Only, and Deep Sleep Control: Disabled
    HPAdvanced → Power-On Options → S4/S5 Wake on LAN: Enable
    LenovoPower → Wake on LAN: Automatic, and turn off Enhanced Power Saving Mode
    OthersLook for “Wake on LAN”, “Power On By PCI-E” or “Resume by PCI-E Device” and turn it on; turn “ErP” or “Deep Sleep” off

  • Power at the wall. A machine needs standby power to wake. A power strip that is switched off, or the switch on the back of the power supply, cuts it.

An encrypted disk stops at its passphrase screen after waking, as it does when you press the power button. The machine is on but waits until someone types the passphrase at it, so it doesn’t come online by itself.

See whether it’s on

bromigos wol status

It lists each wired network card: whether Wake-on-LAN is on, whether a cable is in, and whether the system lets the card wake the machine.

For power users

bromigOS ships these in bromigos-core, on the desktop and on bromigOS Server alike:

FileWhat it does
/usr/lib/NetworkManager/conf.d/50-bromigos-wake-on-lan.confNetworkManager’s default for wired connections: ethernet.wake-on-lan=64 (the “magic” flag). Every connection whose own setting is default follows it
/usr/lib/udev/rules.d/81-bromigos-wake-on-lan.rulesFor each wired card as it appears (at boot, or plugged in): allows the card to wake the machine (device/power/wakeup) and runs ethtool -s <card> wol g. It works without NetworkManager too (bromigOS Server on systemd-networkd)
/usr/lib/bromigos/bin/bromigos-wolbromigos wol status [--json], and sudo bromigos wol apply [CARD…], which turns it on now. The package’s install step runs apply on every install and update
/run/bromigos/wake-on-lan.jsonWhat each wired card says about Wake-on-LAN, written as root by apply and by the udev rule (bromigos wol record). Only root can read that from the network card, so programs that run as you, like BRODEC’s Power on check, read this file instead. No secrets

Only real wired Ethernet cards count: not Wi-Fi, bridges, VPNs or containers’ interfaces.

Check a card by hand (enp3s0 is an example name; ip link lists yours):

nmcli -f 802-3-ethernet.wake-on-lan connection show "Wired connection 1"
cat /sys/class/net/enp3s0/device/power/wakeup     # enabled
ethtool enp3s0 | grep Wake-on                     # Wake-on: g

To turn it off, mask both:

sudo ln -s /dev/null /etc/udev/rules.d/81-bromigos-wake-on-lan.rules
sudo touch /etc/NetworkManager/conf.d/50-bromigos-wake-on-lan.conf   # an empty file shadows the default
sudo ethtool -s enp3s0 wol d

Or keep it on in general and off for one connection: nmcli connection modify "Wired connection 1" 802-3-ethernet.wake-on-lan ignore.

How it’s built: docs/wake-on-lan.md.