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technology/internet/Wake on LAN.md

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+---
+obj: concept
+wiki: https://en.wikipedia.org/wiki/Wake-on-LAN
+arch-wiki: https://wiki.archlinux.org/title/Wake-on-LAN
+---
+
+# Wake on LAN
+Wake-on-LAN (WoL or WOL) is an Ethernet or Token Ring computer networking standard that allows a computer to be turned on or awakened from sleep mode by a network message.
+
+## Magic Packet
+The magic packet is a frame that is most often sent as a broadcast and that contains anywhere within its payload 6 bytes of all 255 (FF FF FF FF FF FF in hexadecimal), followed by sixteen repetitions of the target computer's 48-bit MAC address, for a total of 102 bytes.
+
+Since the magic packet is only scanned for the string above, and not actually parsed by a full protocol stack, it could be sent as payload of any network- and transport-layer protocol, although it is typically sent with [UDP](UDP.md).
+
+### Creating & sending magic packet
+There exists various software for creating magic packets. This is an example in [Python](../programming/languages/Python.md)
+```python
+import socket
+
+def wol(lunaMacAddress: bytes):
+    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+    s.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
+
+    magic = b'\xff' * 6 + lunaMacAddress * 16
+    s.sendto(magic, ('<broadcast>', 7))
+
+if __name__ == '__main__':
+    # pass to wol the mac address of the Ethernet port of the appliance to wakeup
+    wol(b'\x00\x15\xB2\xAA\x5B\x00')
+```
+
+## Setup
+WOL must first be enabled in the UEFI / BIOS of the computer.
+
+### Setup on [Linux](../linux/Linux.md)
+To check and enable WOL on [Linux](../linux/Linux.md) the tool `ethtool` is used.
+
+#### Check if WoL is enabled:
+```
+$ ethtool <interface> | grep Wake-on
+Supports Wake-on: pumbag
+Wake-on: d
+```
+
+If `Supports Wake-on:` only shows `d` WOL is not supported on that interface.
+
+#### Enable WoL with this command:
+```
+ethtool -s <interface> wol g
+```
+
+To enable WOL persistently one can use [Systemd](../linux/Systemd.md):
+
+File: `/etc/systemd/system/wol@.service`
+```toml
+[Unit]
+Description=Wake-on-LAN for %i
+Requires=network.target
+After=network.target
+
+[Service]
+ExecStart=/usr/bin/ethtool -s %i wol g
+Type=oneshot
+
+[Install]
+WantedBy=multi-user.target
+```
+
+Then activate this new service by starting `wol@<interface>.service`.