Thursday, October 25, 2012

HowTo: Xen 4.1.3 Windows 8 HVM domU with Intel HD4000 VGA Passthrough on Debian Wheezy

Update 05/07/2013:
Despite the HowTo being close to 1 year it applies perfectly to this day. At the time Wheezy was Debian's Testing distribution and has since moved to Stable. Much of it can be used to setup other HVM domU such as Linux. 

Important notice: I've experienced some problems with xen-hypervisor-4.1-amd64 versions 4.1.4-3+deb7u1_amd64 and 4.1.4-3_amd64 which implement some security advisory patches . As a result to have sucessful passthrough I was forced to go back to the previous working version: 4.1.4-2_amd64 which is available at Again, do notice that this package is missing some security patches available in more recent versions.
In this HowTo I'll present the steps required to install Xen 4.1.3 using the xm toolstack on a Debian Wheezy (kernel 3.2.0-3-amd64) dom0, create a Windows 8 HVM domU config and setup VGA/PCI Passthrough for the integrated GPU, USB 2.0 controller and audio.

This HowTo assumes that the reader is comfortable with Linux and Windows operating systems namely Debian GNU/Linux and Windows 7/8 as such it doesn't cover the operating systems installation.

For easier reference the procedure will broken down in the following steps:
1) Hardware requirements
2) Install Xen on Debian Wheezy
3) Configure networking
4) Configure Xen
5) Prioritise Xen boot
6) Create and install Windows 8 HVM domU
7) Assign devices for PCI Passthrough
8) Install GPLPV drivers
9) Advices and impressions

1) Hardware requirements

For PCI passthrough both motherboard and CPU must support VT-d also know as IOMMU IO virtualization.

The hardware used to write this HowTo setup is composed of:
  • Intel Core i7-3770 CPU,
  • Intel DQ77MK Motherboard,
  • 32GB GEIL DDR3 1600 MHz,
  • 200GB Maxtor SATA HDD,
  • Samsung SyncMaster 940BW Monitor.

It should be noted that VT-d and VT-x have been enabled in the motherboard and that the i7-3770 integrated GPU is the computer's sole GPU.

In addition to the above setup I've also used another networked computer so I could SSH into the dom0 and perform the steps identified bellow.

2) Install Xen on Debian Wheezy

The Xen hypervisor is provided by the xen-linux-system package:

  1. $ su
  2. # apt-get update
  3. # apt-get install xen-linux-system

3) Configure networking

There are several ways you can provide network access to domU guest domains, the most common being setting up a network bridge which I'll be covering.

To assign a static IP to the dom0 and define a network bridge named eth0, disable NetworkManager (if installed) and edit /etc/network/interfaces to contain a bridge:

  1. # /etc/init.d/network-manager stop
  2. # update-rc.d network-manager disable
  3. # aptitude install bridge-utils
  4. # vim /etc/network/interfaces auto lo br0 iface lo inet loopback allow-hotplug eth0 iface eth0 inet manual iface br0 inet static bridge_ports eth0 address broadcast netmask gateway
  5. # vim /etc/resolv.conf domain nameserver is the IP chosen to be assigned to the host, and are the typical broadcast and netmask values for a 192.168.1.x network and in my case the gateway is Replace this values according to your own network settings and desires.

4) Configure Xen

The xend daemon employs xend-config.sxp to determines the parameters that Xen should use.

Personally I choose to disable dom0 ballooning, define the dom0 assignable memory and change the keyboard layout (I've changed mine to pt):

  1. # vim /etc/xen/xend-config.sxp (dom0-min-mem 2048) (enable-dom0-ballooning no) (keymap 'pt')

I've restricted the amount of memory assigned to dom0 to 2048 MB. In my case the dom0 is headless and all the hard work is to be done by the non-privileged virtual machines as such I've opted for a comfortable amount of memory to be assigned to the dom0, 2048 MB (2 GB). To this end GRUB needs to pass the appropriate command as the hypervisor boots:

  1. # echo 'GRUB_CMDLINE_XEN="dom0_mem=2G,max:2G"' >> /etc/default/grub
  2. # update-grub2

5) Prioritise Xen boot

By default Wheezy's GRUB lists and boots regular kernels and afterwards the Xen hypervisor.

Assuming that the computer is to be running Xen all the time it advisable to change this behaviour and increase Xen's GRUB boot priority so that it's the first on the list and boots by default.

The Debian way to do this is to used dpkg-divert like so:

  1. # dpkg-divert --divert /etc/grub.d/08_linux_xen --rename /etc/grub.d/20_linux_xen
  2. # update-grub2

To undo this necessary:
  1. # dpkg-divert --rename --remove /etc/grub.d/20_linux_xen
  2. # update-grub2

6) Create and install Windows 8 HVM domU

The xm toolstack uses configuration files that define the domain meaning that we need to create a configuration file for our guest VM:

  1. # vim /etc/xen/win8-x64.cfg kernel = 'hvmloader' builder = 'hvm' vcpus = '4' memory = '4096' disk = ['file:/srv/xen/domains/win8-x64.img,hda,w',
    'file:/srv/xen/images/Windows8-ReleasePreview-32bit-English.iso,hdc:cdrom,r'] name = 'win8-x64' vif = [ 'mac=00:16:3E:51:20:4C,bridge=br0,model=e1000' ] on_poweroff = 'destroy' on_reboot = 'restart' on_crash = 'restart' boot = 'dc' acpi = '1' apic = '1' viridian = '1' xen_platform_pci='1' sdl = '0' vnc = '1' vnclisten = '' vncpasswd = '' stdvga = '0' usb = '1' usbdevice = 'tablet'

Do note that a MAC address must be assigned to the virtual interface. The 00:16:3e MAC block is reserved for Xen domains, do the last three digits may be randomly filled in (hex values 0-9 and a-f only).

In this HowTo I'm using file based storage which implies using the dd command to create what will be the domU hard drive. To create a 40GB .img file:

  1. # dd if=/dev/zero of=/srv/xen/domains/win8-x64.img bs=1M count=40960

If you're using LVM use 'phy:/dev/mapper/win8-x64,hda,w' (change according to your own target logical volume) instead of 'file:/srv/xen/domains/win8-x64.img,hda,w'.

For more on the options that the domain configuration file accepts refer to xmdomain.cfg.

There are 2 options when it comes to actually installing Windows 8 on the virtual machine. One method consists in using VNC to connect to the guest virtual machine and installing the operating system from whatever computer you have with a graphical desktop environment. In alternative, one can use VGA Passthrough for the install process altogether.

Choose one of the methods, though the VNC method is preferable as it eases troubleshooting and it's the one documented bellow. To use the VGA Passthrough method jump to step 7 of the HowTo and issue xm create win8-x64.cfg.

After defining Windows 8 domU configuration file execute it and connect through VNC to install Windows 8:

  1. # xm create win8-x64.cfg
  2. $ vncviewer

If running a GUI on dom0 simply vncviwer, however if running from a networked computer replace the localhost with the IP of the said networked computer ( for example).

Proceed to do a Windows install, shutdown the guest VM and backup the .img for future use. To shutdown the Windows 8 HVM domU either use guest's shutdown button or issue:

  1. # xm destroy win8-x64

xm list can be used to find out the domain Id and use it as argument for xm destroy, for example:

  1. xm listName         ID Mem VCPUs State   Time(s)Domain-0     0 4096 8     r-----   34476.9win8-x64     4 4096 4     -b----   301.0
  2. xm destroy 4

Also comment out the cdrom line so that the virtual machine doesn't boot into the Windows installation cdrom every time it boots. For security reasons it is best to disable VNC.

  1. # vim /etc/xen/win8-x64.cfg kernel = 'hvmloader' builder = 'hvm' vcpus = '4' memory = '4096' disk = ['file:/srv/xen/domains/win8-x64.img,hda,w',
    #'file:/srv/xen/images/Windows8-ReleasePreview-32bit-English.iso,hdc:cdrom,r'] name = 'win8-x64' vif = [ 'mac=00:16:3E:51:20:4C,bridge=br0,model=e1000' ] on_poweroff = 'destroy' on_reboot = 'restart' on_crash = 'restart' boot = 'dc' acpi = '1' apic = '1' viridian = '1' xen_platform_pci='1' sdl = '0' vnc = '0' vnclisten = '' vncpasswd = '' stdvga = '0' usb = '1' usbdevice = 'tablet'

7) Assign devices for PCI Passthrough

A domU can be made aware and directly access and use PCI devices with full privileges. To accomplish that the PCI devices need to be hidden from the dom0 and not be forwarded to any other domUs.

Using the xm toolstack this is achieved loading the pci_stub kernel module, identifying the PCI devices that are to be forwarded, unbinding the device from dom0 and bind it to pci_stub thus allowing it to be assigned in the domU config file.

  1. # lspci 00:00.0 Host bridge: Intel Corporation Xeon E3-1200 v2/3rd Gen Core processor DRAM Controller (rev 09) 00:02.0 VGA compatible controller: Intel Corporation Xeon E3-1200 v2/3rd Gen Core processor Graphics Controller (rev 09) 00:14.0 USB controller: Intel Corporation 7 Series/C210 Series Chipset Family USB xHCI Host Controller (rev 04) 00:16.0 Communication controller: Intel Corporation 7 Series/C210 Series Chipset Family MEI Controller #1 (rev 04) 00:16.3 Serial controller: Intel Corporation 7 Series/C210 Series Chipset Family KT Controller (rev 04) 00:19.0 Ethernet controller: Intel Corporation 82579LM Gigabit Network Connection (rev 04) 00:1a.0 USB controller: Intel Corporation 7 Series/C210 Series Chipset Family USB Enhanced Host Controller #2 (rev 04) 00:1b.0 Audio device: Intel Corporation 7 Series/C210 Series Chipset Family High Definition Audio Controller (rev 04) 00:1c.0 PCI bridge: Intel Corporation 7 Series/C210 Series Chipset Family PCI Express Root Port 1 (rev c4) 00:1c.6 PCI bridge: Intel Corporation 7 Series/C210 Series Chipset Family PCI Express Root Port 7 (rev c4) 00:1d.0 USB controller: Intel Corporation 7 Series/C210 Series Chipset Family USB Enhanced Host Controller #1 (rev 04) 00:1e.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev a4) 00:1f.0 ISA bridge: Intel Corporation Q77 Express Chipset LPC Controller (rev 04) 00:1f.2 SATA controller: Intel Corporation 7 Series/C210 Series Chipset Family 6-port SATA Controller [AHCI mode] (rev 04) 00:1f.3 SMBus: Intel Corporation 7 Series/C210 Series Chipset Family SMBus Controller (rev 04) 02:00.0 Ethernet controller: Intel Corporation 82574L Gigabit Network Connection 03:03.0 FireWire (IEEE 1394): LSI Corporation FW322/323 [TrueFire] 1394a Controller (rev 70)

I'll be forwarding 00:02.0 VGA compatible controller, 00:1b.0 Audio device and 00:1d.0 USB controller. To know the exact numbering of the devices run lspci -n:

  1. # lspci -n 00:00.0 0600: 8086:0150 (rev 09) 00:02.0 0300: 8086:0162 (rev 09) 00:14.0 0c03: 8086:1e31 (rev 04) 00:16.0 0780: 8086:1e3a (rev 04) 00:16.3 0700: 8086:1e3d (rev 04) 00:19.0 0200: 8086:1502 (rev 04) 00:1a.0 0c03: 8086:1e2d (rev 04) 00:1b.0 0403: 8086:1e20 (rev 04) 00:1c.0 0604: 8086:1e10 (rev c4) 00:1c.6 0604: 8086:1e1c (rev c4) 00:1d.0 0c03: 8086:1e26 (rev 04) 00:1e.0 0604: 8086:244e (rev a4) 00:1f.0 0601: 8086:1e47 (rev 04) 00:1f.2 0106: 8086:1e02 (rev 04) 00:1f.3 0c05: 8086:1e22 (rev 04) 02:00.0 0200: 8086:10d3 03:03.0 0c00: 11c1:5811 (rev 70)

For each PCI to be forwarded create a pci-stub Id, unbind it from the dom0 and bind to pci-stub. xm pci-list-assignable-devices is useful in confirming if the device has been added to the pool of devices that can be assigned to a guest domain.

  1. # modprobe pci_stub
  2. # echo "8086 1e26" > /sys/bus/pci/drivers/pci-stub/new_id
  3. # echo "0000:00:1d.0" > /sys/bus/pci/devices/0000\:00\:1d.0/driver/unbind
  4. # echo "0000:00:1d.0" > /sys/bus/pci/drivers/pci-stub/bind
  5. # xm pci-list-assignable-devices 0000:00:1d.0
  6. # echo "8086 0162" > /sys/bus/pci/drivers/pci-stub/new_id
  7. # echo "0000:00:02.0" > /sys/bus/pci/devices/0000\:00\:02.0/driver/unbind
  8. # echo "0000:00:02.0" > /sys/bus/pci/drivers/pci-stub/bind
  9. # xm pci-list-assignable-devices 0000:00:02.0 0000:00:1d.0
  10. # echo "8086 1e20" > /sys/bus/pci/drivers/pci-stub/new_id
  11. # echo "0000:00:1b.0" > /sys/bus/pci/devices/0000\:00\:1b.0/driver/unbind
  12. # echo "0000:00:1b.0" > /sys/bus/pci/drivers/pci-stub/bind
  13. # xm pci-list-assignable-devices 0000:00:02.0 0000:00:1b.0 0000:00:1d.0

Do note that the devices won't be available in the dom0, that's why typical VGA Passthrough setups involve 2 or more graphics cards forwarding the more powerful to the domU alongside an USB controller and audio (I'll cover Secondary Display Adapter PCI passthrough in a future post). In this case only the CPU's integrated GPU is present so as soon has 00:02.0 VGA compatible controller is hidden for the dom0 it can't be used by it and thus the only way to be access is via another computer using SSH for example.

Update the domU's configuration file with the devices that are to be used and start the Windows 8 domU by issuing xm create win8-x64.cfg.

  1. # vim /etc/xen/win8-x64.cfg kernel = 'hvmloader' builder = 'hvm' vcpus = '4' memory = '4096' disk = [ 'file:/srv/xen/domains/win8-x64.img,hda,w', #'file:/srv/xen/images/Windows8-ReleasePreview-32bit-English.iso,hdc:cdrom,r' ] name = 'win8-x64' vif = [ ',mac=00:16:3E:51:20:4C,bridge=br0,model=e1000' ] on_poweroff = 'destroy' on_reboot = 'restart' on_crash = 'restart' boot = 'dc' acpi = '1' apic = '1' viridian = '1' xen_platform_pci='1' sdl = '0' vnc = '0' vnclisten = '' vncpasswd = '' stdvga = '0' usb = '1' usbdevice = 'tablet' pci = [ '00:1d.0', '00:1b.0' , '00:02.0' ]
  2. # xm create win8-x64.cfg

Also consider creating a script to automate loading pci-stub and unbinding/binding the  PCI devices.

8) Install GPLPV drivers

Developed by James Harper, GPLPV drivers allow swapping the QEMU emulated devices for paravirtualized devices. With these new devices I/O speeds are improved as Windows will use the network and block backend drivers present in the dom0.

Signed GPLPV drivers are available at Windows 8 32-bit can be downloaded at while 64-bit drivers are available at
Vista2008 in the drivers' installer filename means that it applies to the recent Windows releases (e.g. Vista/2008/7/8).

9) Advices and impressions

I've written some pieces of advices and impressions over using XEN over at with some specific Intel HD4000 VGA Passthrough so make sure to read them.

Wheezy's stock kernel doesn't contain xen-acpi-processor as it was introduced during Linux kernel 3.4.x as such power management is lacking. In this scenario, consider compiling the kernel or in alternative installing Debian Experimental's kernel. The latter option implies editing /etc/apt/sources.list to cover the experimental branch and instructing apt-get to install the kernel package from the experimental distribution.

Xen is at version 4.1.3 in Debian Wheezy's repository however the recent 4.2.0 release is already available in the experimental branch. And with the 4.2.0 comes xl, the new toolstack set to replace xm.

In the coming weeks I'll update this HowTo with the required steps to combine Debian Experimental Xen and Linux kernel packages with the testing distribution.

Update 05/07/2013:
I've moved on from HD4000 VGA passthrough and am currently using PCI passthrough on 2 AMD cards (HD7850 and HD5450) with much success. The HD5450 is assigned to a Fedora 19 domU while the HD7850 is assigned to a Windows 8 domU (Catalyst drivers aren't installed) for my gaming fix. 
Stability of the setup: rock solid. dom0 is typically online for 1 to 2 months without rebooting, the Fedora 19 is hardly rebooted or shutdown while the Windows 8 domU is shutdown at night. Aside from these domU another Windows 8 domU is allways on.

Thursday, August 16, 2012

Tip: Assign Xen dom0 memory on Debian Wheezy

Though Xen can manage memory with the ballon driver it is considered good practice to limit/restrict the amount of memory assigned to dom0. Doing so will stop the  Linux kernel from wasting memory.

To do so you'll need to pass the appropriate boot parameter for both the Xen hypervisor and Linux.

As an example, let's assume you want to assign 2GB to your dom0 here's how:
  1. $ su
  2. # echo 'GRUB_CMDLINE_XEN="dom0_mem=2G,max:2G"' >> /etc/default/grub
  3. # update-grub2

The above steps were executed on Debian Wheezy running Xen 4.1.3 but should translate as well to any other distribution running Xen 4.1.2 or latter and GRUB2. Users of GRUB will need to edit grub.conf and pass down the boot parameters in an analogous manner.

Tuesday, July 17, 2012

Tip: Fixing "gnome-screenshot" (No such file or directory) on CentOS 6.3

While pressing Prnt Scrn to take a window screenshot I got awarded with "cool" Metacity message window stating the following:

  1. There was an error running gnome-screenshot:Failed to execute child process "gnome-screenshot" (No such file or directory)

I'm running a fresh CentOS 6.3 system installed using the x86_64 Live CD which shortly after installing it noticed that it didn't came with Disk Usage Analyzer. Putting the error message and the missing application points the problem to the package that provides both gnome-utils.

To fix the problem and also install the other missing applications:
  1. $ su
  2. # yum install gnome-utils -y

And that's it!

Tip: Blacklisting kernel modules on CentOS 6.3

While trying the kernel-ml from the ELRepo repository I noticed that it ships with the pcspkr.ko kernel module which is in my opinion pretty annoying. 

To unload a kernel module, for instances pcspkr.ko, simply issue the rmmod command with the kernel module as argument. However this will only take place for the current session, the next time you reboot the machine hte kernel module will load. To prevent this we need to blacklist it by adding it to /etc/modprobe.d/blacklist.conf.

Putting everything together:

  1. $ su
  2. # rmmod -v pcspkr
  3. # echo "blacklist pcspkr" >> /etc/modprobe.d/blacklist.conf

On step 1 we've changed to superuser, on step 2 the kernel module (pcspkr was selected as an example) was removed from the current session and on step 3 we've prevented it from loading at boot.

As a side note, to list the currently loaded kernel modules run lsmod.

Sunday, July 15, 2012

Tip: Remove xen-runtime from kernel-xen repository

Lately I've been messing with Xen.

In the process of using the kernel-xen repository I came across the following situation while attempting to uninstall xen-runtime:
  1. # yum remove xen-runtime
    Loaded plugins: fastestmirror, refresh-packagekit, security
    Setting up Remove Process

    Resolving Dependencies

    --> Running transaction check
    ---> Package xen-runtime.x86_64 0:4.1.2-8.el6 will be erased
    --> Finished Dependency Resolution
    Dependencies Resolved
      Package Arch Version Repository Size
    ================================================================== Removing:
      xen-runtime x86_64 4.1.2-8.el6 @kernel-xen 8.0 M

    Transaction Summary
    Remove 1 Package(s)

    Installed size: 8.0 M
    Is this ok [y/N]: y
    Downloading Packages:
    Running rpm_check_debug
    Running Transaction Test
    Transaction Test Succeeded
    Running Transaction
    Error in PREUN scriptlet in rpm package xen-runtime
    xen-runtime-4.1.2-8.el6.x86_64 was supposed to be removed but is not!
      Verifying : xen-runtime-4.1.2-8.el6.x86_64 1/1

      xen-runtime.x86_64 0:4.1.2-8.el6
  2. # rpm -e xen-runtime
    /var/tmp/rpm-tmp.LcPd6z: line 5: /bin/systemctl: No such file or directory
    error: %preun(xen-runtime-4.1.2-8.el6.x86_64) scriptlet failed, exit status 127

To remove the little bastard the --nopreun needs to be passed down to rpm -e. By doing so the execution of the %preun scriptlet is turned off thus allowing rpm to uninstall the offending package, like so:
  1. # rpm -e --nopreun xen-runtime


Now I can go back to messing with Xen ;)

Saturday, July 14, 2012

HowTo: Install Adobe Flash Player using Repoforge on CentOS 6.3

To install Adobe Flash Player on RHEL or CentOS 6.3 using the Repoforge repository, you'll need to change to root, import repository's GPG key, install the repository file and install the Adobe Flash Player package.

If you're running a 32 bits system:
  1. $ su
  2. # rpm --import
  3. # rpm -Uvh
  4. # yum install flash-plugin

On the other hand, if you have a 64 bits install issue the following commands:
  1. $ su
  2. # rpm --import
  3. # rpm -Uvh
  4. # yum install flash-plugin

Launch Mozilla Firefox and in the address bar enter about:plugins. An Shockwave Flash entry should be available.

If you point to System -> Preferences you'll notice that a new entry named Adobe Flash Player is now available.

You can test if the plugin is working by visiting or by firing up a random Youtube clip.

If you'd prefer to using Adobe's own YUM repository follow the steps described in and for 64 and 32 bit systems, respectively.

Monday, July 9, 2012

HowTo: Enable Wake-on-LAN on CentOS / SL 6.3

Wake-on-LAN also know as WOL is the ability to switch on a computer that is connected to a network (local or not) by means of a special network message called a magic packet. This magic packet contains the MAC address of the destination computer. If the destination computer has a network interface card that support WOL then the system wakes up.

In this post I'll describe how to setup a CentOS destination computer so that it can be turned on from another computer. This procedure is also applicable to RHEL and its clones such as Scientific Linux and Oracle Unbreakable Linux.

For sake of simplicity I've broken down the procedure into a few steps:
1) Enable WOL in BIOS
2) Collect network interface information
3) Enable WOL for the next shutdown
4) Make WOL always enabled
5) Wake up the computer from local network
6) Wake up the computer from internet
7) Troubleshooting

1) Enable WOL in BIOS

These days pretty much all integrated or otherwise NICs support Wake-on-LAN, however more often than not you'll need to enable it in the BIOS. There are literally hundreds of BIOS around but look for the typical options: "Enable Wake-on-LAN", "Enable Wake on PCI" and "Enable Power of PCIE Devices".

2) Collect network interface information

Start by checking if the destination computer network card support Wake-on-LAN with ethtool:
  1. $ ifconfig
    eth0      Link encap:Ethernet  HWaddr 00:11:AA:22:BB:22 
              inet addr:  Bcast:  Mask:
              inet6 addr: fc70::151:8daa:fbab:f14a/64 Scope:Link
              UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
              RX packets:563668 errors:0 dropped:0 overruns:0 frame:0
              TX packets:317604 errors:0 dropped:0 overruns:0 carrier:0
              collisions:0 txqueuelen:1000
              RX bytes:813741621 (776.0 MiB)  TX bytes:68592900 (65.4 MiB)
              Interrupt:22 Base address:0xa000

    lo        Link encap:Local Loopback 
              inet addr:  Mask:
              inet6 addr: ::1/128 Scope:Host
              UP LOOPBACK RUNNING  MTU:16436  Metric:1
              RX packets:8 errors:0 dropped:0 overruns:0 frame:0
              TX packets:8 errors:0 dropped:0 overruns:0 carrier:0
              collisions:0 txqueuelen:0
              RX bytes:480 (480.0 b)  TX bytes:480 (480.0 b)
  2. $ su
  3. # ethtool eth0
    Settings for eth0:
        Supported ports: [ MII ]
        Supported link modes:   10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
        Supports auto-negotiation: Yes
        Advertised link modes:  10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
        Advertised pause frame use: No
        Advertised auto-negotiation: Yes
        Speed: 100Mb/s
        Duplex: Full
        Port: MII
        PHYAD: 1
        Transceiver: external
        Auto-negotiation: on
        Supports Wake-on: g
        Wake-on: d
        Link detected: yes

The "Supports Wake-on: g" string means that the NIC does in fact support Wake-on-LAN while "Wake-on: d" is a sign that the feature is not turned activated in the operating system.

Do notice that the target of ethtool was eth0 which is my destination computer's network interface name.

To use Wake-on-LAN we need to identify the NIC MAC address to which end ifconfig can be used:
  1. # ifconfig | grep HWaddreth0 Link encap:Ethernet HWaddr 00:11:AA:22:BB:22

3) Enable WOL for the next shutdown

To command the operating system to enable WOL for the eth0 network interface run:
  1. # ethtool -s eth0 wol g

Issuing ethtool again now returns "Wake-on: g" so now we have WOL enabled:
  1. # ethtool eth0
    Settings for eth0:
        Supported ports: [ MII ]
        Supported link modes:   10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
        Supports auto-negotiation: Yes
        Advertised link modes:  10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
        Advertised pause frame use: No
        Advertised auto-negotiation: Yes
        Speed: 100Mb/s
        Duplex: Full
        Port: MII
        PHYAD: 1
        Transceiver: external
        Auto-negotiation: on
        Supports Wake-on: g
        Wake-on: g
        Link detected: yes

4) Make WOL always enabled

To have WOL always enabled the operating system needs to be told that eth0 (this is my NIC's interface name, don't forget to change according to your own system) WOL is supposed to be active.

There are 2 methods to achieve this, one employs adding ethtool -s eth0 wol g command to /etc/rc.d/rc.local while the other consists in creating a network script and enabling the network service.

Choose one of the methods, personally I'd go for the /etc/rc.d/rc.local method as it requires less typing ;)

Method A

  1. #echo '/usr/sbin/ethtool -s eth0 wol g' >> /etc/rc.d/rc.local

Method B
  1. # vim /etc/sysconfig/network-scripts/ifcfg-eth0
    ONBOOT=yesETHTOOL_OPTS="wol g"
  2. # chkconfig network on

5) Wake up the computer from local network

From the computer that will be used to send the magic WOL packet, install and run wakelan:

  1. # yum install wakelan
  2. # rehash
  3. # wakelan 00:11:AA:22:BB:22

6) Wake up the computer from internet

This involves enabling port forwarding of UDP port 9 to the destination computer in the router's administration webpage. To fully benefit from WOL you should configure a dynamic DNS service.

Afterwards to issue the wake up command you can use websites such as, Android applications (Wake on Lan) or any other Wake-on-LAN application (every Unix-like system as an alternative available). Just make sure to use your dynamic DNS provided address and the destination computer's MAC.

7) Troubleshooting

While troubleshooting Wake-on-LAN I've noticed that if you use GRUB without timeout set and poweroff the computer while on the operating system selection menu, the next time you try to use Wake-on-LAN it won't work. So make sure you have GRUB with a timeout set (which is the case will all default installation of GRUB).

If the computer is disconnected from the power supply you'll need to boot the computer and turn off again so that the NIC assumes the WOL definitions.