Wake on lan linux команда

Enabling Wake-On-LAN (In Ubuntu 20.10)

Note: The systemd configuration here isn’t quite right, but since this post is kind of long and convoluted I made a standalone update about the systemd configuration file in this post.

Beginning

These are my notes on getting Wake-On-LAN working in Ubuntu 20.10. I have a server that I use to run most of the computation on when I use emacs/jupyter but I have it in a corner upstairs and although it’s only a little walk, I find that the fact that I have to stop what I’m doing and go upstairs to push that little button on the front makes me lazy and so it ends up running more than it has to so I thought I’d enable Wake-On-LAN so I can suspend it and wake it up whenever I need to. I’m only going to use suspend (APM S3). When I tried to use hibernate (S4) it ended up shutting down my machine (S5). Interestingly, my BIOS menu has an option to enable waking up from shutdown, but since my disk is encrypted, and I didn’t set up a separate SSH server, I have to go enter the passphrase to unlock the disk before the operating system can boot up, so it kind of defeats its own purpose.

Middle

Ethtool

The command I used to set up Wake-On-LAN on the remote machine is called ethtool. It’s in the Ubuntu repositories but wasn’t installed on my machine so I had to add it.

Checking the Interface

From what I’ve read, not all ethernet interfaces support Wake-On-LAN (although I’ve never seen one that doesn’t) so a quick check might be useful. First, find the name of your ethernet interface.

My machine shows four interfaces so I’ll just show the output for the interface I’m interested in rather than the whole output for the command.

2: enp4s0: mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether 38:d5:47:79:ab:0b brd ff:ff:ff:ff:ff:ff inet 192.168.86.97/24 brd 192.168.86.255 scope global dynamic noprefixroute enp4s0 valid_lft 84752sec preferred_lft 84752sec inet6 fe80::685d:374d:a577:f787/64 scope link noprefixroute valid_lft forever preferred_lft forever

Ethtool uses the name of the interface, in this case it’s enp4s0 , so we’ll need to note that. Additionally, the machine that I used to wake up the machine needs the MAC address ( 38:d5:47:79:ab:0b ) so it’d be useful to write that down someplace. I’m waking it up from the LAN so the IP address isn’t so important, and to be able to SSH into it I need to know it anyway, so it’s really those two pieces of information that I need. Now to check if it supports Wake-On-LAN.

Ethtool will give you some information if you don’t run it as root but for Wake-On-LAN you need to run it as root. The important lines in the output is near the bottom and it looks something like this if it supports Wake-On-LAN.

Supports Wake-on: pumbg Wake-on: d

The man-page for ethtool tell you what that cryptic pumbg means — the letters are different options that this interface supports for Wake-On-LAN. In this case they are:

There’s an additional option which is what the interface was set on – d – as you can see in the last line of the output. This means Disable (wake on nothing). This option clears all previous options. I don’t have many devices on my network, so I don’t know that there’s a lot of broadcasts, multicasts, etc. that would be waking it up all the time, but since one feature of Wake-On-LAN is that it only wakes the machine when it gets the «Magic Packet», only the g and d options matter. Now that I knew it was supported, it was time to try it out.

Turn It On Temporarily

The ethtool will turn on Wake-On-LAN, but (supposedly) everytime you reboot the machine it will reset to disabled. I haven’t really tested this out, but I’ll document how to make it permanent later, anyway.

sudo ethtool --change enp4s0 wol g

So, as you might guess, we changed the Wake-On-LAN setting to listen for MagicPacket messages. You can check using the ethtool again.

The Wake-on line should have changed to:

Now to suspend the machine so we can test it out.

Test It Out

Now, on my local machine I needed to install wakeonlan. There’s a surprising number of programs to send the Magic Packet, but this just happened to be the one I used.

sudo apt install wakeonlan

The default way to use wakeonlan is apparently to just pass it the MAC address of the computer to wake up, and it will send the Magic Packet out as a broadcast, so that’s what I did.

And then I pinged the machine and I waited. And I waited. And I waited… Eventually I went upstairs and saw that it was still sleeping so I pushed the power button to wake it up and went back downstairs.

Take Two

Something wasn’t right so I SSHd into the server and started up tcpdump to see if the packets were going through.

sudo tcpdump -i enp4s0 '(udp and port 7) or (udp and port 9)'

Which gave me this output:

tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on enp4s0, link-type EN10MB (Ethernet), capture size 262144 bytes

And then I sent the Magic Packet again.

…And nothing happened. For some reason the packets weren’t getting picked up by the machine. Luckily, wakeonlan lets you pass in an IP address as an option. The man page recommends using a broadcast address, but I have the IP addresses of my machines on the LAN reserved on my router/access-point so I just passed in the full address (I did try the LAN broadcast and it worked too).

wakeonlan -i erebus 38:d5:47:79:ab:0b

I have my machine’s IP address aliased in my /etc/hosts file so erebus is just an alias for the machine’s IP address. The subnet broadcast version looked like this.

wakeonlan -i 192.168.86.255 38:d5:47:79:ab:0b

The output from tcpdump for the first packet looked like this.

tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on enp4s0, link-type EN10MB (Ethernet), capture size 262144 bytes 20:47:11.689587 IP 192.168.86.141.34805 > erebus.discard: UDP, length 102

So, something was different. I suspended the machine again and sent the Magic Packet and this time it worked. Go figure.

Making It Permanent

Set It Up

The reasons that I said earlier that the Wake-On-LAN setting «supposedly» is temporary is that:

1. I haven’t really re-booted that machine to test it out (I have rebooted, but I haven’t disable the systemd service that I’m documenting here).
2. The machine that I’m typing this on had Wake-On-LAN enabled and it doesn’t have a systemd service enabled.

But, really, I don’t remember even enabling Wake-On-LAN on this machine so maybe it just was the default and I didn’t realise it… another thing I should look into one of these days. Anyway, to make a service that always enables Wake-On-LAN the first step is to find the path to ethertool .

In my case the path was /sbin/ethtool , so once you know this you can create a file at /etc/systemd/system/wol.service (I think you can use another systemd sub-folder, and you can name the file anything you want, within reason, but this one seems to work well enough). In this file you put settings that look something like this:

[Unit] Description=Enable Wake On Lan [Service] Type=oneshot ExecStart = /sbin/ethtool --change enp4s0 wol g [Install] WantedBy=basic.target

The only thing specific to my machine is enp4s0 , the name of the ethernet interface, although it’s possible that the path to the ethtool executable might be different too… but it should be the same on Ubuntu 20.10, anyway.

Enable The Service

To enable it you can do this:

sudo systemctl daemon-reload sudo systemctl enable wol.service

Where wol.service is the name of the file you created with the settings. You can check its status if you want.

End

So, that’s how I got one machine working with Wake-On-LAN. Hopefully I won’t have to look so hard the next time. Here’s the pages that I stole this from.

• TechRepublic on using ethtool and setting up a systemd service for this (don’t use the systemd file here, though).
• Stack Overflow on how to suspend and hibernate from the command-line
• Stack Overflow on what the difference is between suspend and hibernate
• Stack Overflow on using tcpdump to look for the Magic Packets on the remote machine
• Stack Overflow on editing remote files as root with emacs (not documented here, but maybe later)
• Stack Overflow on editing a local file as root with emacs (not used here, but I can never remember the syntax)

Источник

WakeOnLan

This page explains how to enable use of Wake-on-LAN (WoL) in systems that have Ubuntu installed.

Introduction

Wake-on-LAN enables users to turn on a computer across a network from another network device. It can be very useful in situations where computers are not all next to each other or there are a lot of machines. WoL works by sending a packet of data called a Magic Packet™ to the target machine. When the packet is received, the target machine’s network device (Network Interface Controller or NIC) wakes-up the rest of the machine.

Setting Up Wake-on-LAN

In order to use WoL it must be supported and enabled as necessary in the BIOS, NIC and other network hardware (routers, switches etc). You may also need to configure some software if things don’t work out-of-the-box.

Enabling WoL in the BIOS

This section may differ depending on whether or not you have a NIC integrated into your motherboard.

Using an Integrated NIC

To enable WoL in the BIOS, enter the BIOS setup and look for something called «Wake up on PCI event», «Wake up on LAN» or similar. Change it so that it is enabled. Save your settings and reboot.

Using a Non-Integrated NIC

If your NIC is not integrated into your motherboard, you will still have to configure your BIOS to allow devices to wake up your computer. Boot your computer and enter the BIOS settings menu. In one of the sub-menus there will hopefully be the option to allow USB and/or PCI devices to wake-up the computer. Enable the setting that is appropriate for your NIC. Save your settings and reboot.

PCI NICs sometimes require a cable connection to the power supply in order to stay awake when the computer is off/asleep. Check your manual to see if yours does and install if necessary.

Enabling WoL in the NIC

Determining whether the NIC supports WoL

First, determine which NIC will be used, and then check whether it supports the Magic Packet™ using

where is the device name of your NIC, e.g. eth0. This command will output some information about your the capabilities of your NIC. If this output contains a line similar to the following:

where contains the letter g, the NIC should support the WoL Magic Packet™ method (for the other letters look at man ethtool).

shahar@shahar-backup:~$ cat /etc/network/interfaces # This file describes the network interfaces available on your system # and how to activate them. For more information, see interfaces(5). # The loopback network interface auto lo iface lo inet loopback # The primary network interface auto eth0 iface eth0 inet static address 10.0.0.1 netmask 255.255.255.0 gateway 10.0.0.138 up ethtool -s eth0 wol g