70 lines
2.2 KiB
Markdown
70 lines
2.2 KiB
Markdown
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---
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obj: concept
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wiki: https://en.wikipedia.org/wiki/Wake-on-LAN
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arch-wiki: https://wiki.archlinux.org/title/Wake-on-LAN
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---
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# Wake on LAN
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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.
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## Magic Packet
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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.
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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).
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### Creating & sending magic packet
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There exists various software for creating magic packets. This is an example in [Python](../programming/languages/Python.md)
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```python
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import socket
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def wol(lunaMacAddress: bytes):
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s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
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s.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
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magic = b'\xff' * 6 + lunaMacAddress * 16
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s.sendto(magic, ('<broadcast>', 7))
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if __name__ == '__main__':
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# pass to wol the mac address of the Ethernet port of the appliance to wakeup
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wol(b'\x00\x15\xB2\xAA\x5B\x00')
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```
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## Setup
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WOL must first be enabled in the UEFI / BIOS of the computer.
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### Setup on [Linux](../linux/Linux.md)
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To check and enable WOL on [Linux](../linux/Linux.md) the tool `ethtool` is used.
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#### Check if WoL is enabled:
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```
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$ ethtool <interface> | grep Wake-on
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Supports Wake-on: pumbag
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Wake-on: d
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```
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If `Supports Wake-on:` only shows `d` WOL is not supported on that interface.
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#### Enable WoL with this command:
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```
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ethtool -s <interface> wol g
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```
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To enable WOL persistently one can use [Systemd](../linux/Systemd.md):
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File: `/etc/systemd/system/wol@.service`
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```toml
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[Unit]
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Description=Wake-on-LAN for %i
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Requires=network.target
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After=network.target
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[Service]
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ExecStart=/usr/bin/ethtool -s %i wol g
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Type=oneshot
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[Install]
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WantedBy=multi-user.target
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```
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Then activate this new service by starting `wol@<interface>.service`.
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