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I use VirtualBox to run a Ubuntu x64 guest under a Vista x64 host with a 19" and 15" monitor.

I enable seamless mode in VirtualBox, but the windows don't actually move anywhere other than the desktop of the Ubuntu guest.

I'd also like fullscreen mode to display across both monitors.

How can I do this?

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up vote 16 down vote accepted

According to this forum post and looking through the VirtualBox release notes this is only available to Windows Guests. I know the latest 3 release introduced huge improvements on the 3D rendering side and with OpenGL. I would assume this would be available in the near future.

And according to the 4.0 release notes, the feature is available!

Guest Additions: support for multiple virtual screens in Linux and Solaris guests using X.Org server 1.3 and later
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As of 4.0 Beta 2, this feature is now available to clients running version 1.3+... if you are feeling adventurous. – Goyuix Dec 9 '10 at 23:50
Now that 4.0.2 is out, this feature is in, right? No need to be adventurous? – Nate Parsons Feb 3 '11 at 19:11
I just tried it and multiple monitors works fine for me with Ubuntu 10.10 -I didn't even know Virtual Box 4.x added support for Linux guests - I gave up on checking with every release. – jmohr Feb 3 '11 at 20:33
@drhorrible Thanks for updating my answer, I forgot about this altogether and haven't used VirtualBox in about a year. – BinaryMisfit Feb 3 '11 at 20:36
No problem, I'm just coming back after learning this feature is present, very excited! This is my first step towards going to Linux as primary. – Nate Parsons Feb 3 '11 at 20:49

My solution involves running Ubuntu in headless mode and connecting through the Remote Desktop Connection tool. The display is full screen (no toolbars or menus) and spans both of my monitors. Here's what I did:

  1. Double video memory to 16 MB in VirtualBox display settings for the machine. Also enable "Remote Display" server. For some reason I couldn't use the default port of 3389.
  2. Run the machine in headless mode like this:

    VBoxHeadless.exe --startvm "Ubuntu 10.4 64-bit"

  3. Connect to the machine using the Remote Desktop Connection tool that comes with Windows.

    mstsc /span /v:

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Assuming you have the guest additions... You can get an approximate full screen across 2 monitors if you edit your xorg.conf file (I run FC11... I'm not sure if ubuntu uses xorg.conf?) and then just manually stretch the window to fill both. This definitely isnt ideal, but it does get you more visible desktop space.

I have two monitors in windows they run at 1440x900 and 1280x1024 respectively. The setup below allows a max screen size of 32000x32000.

You then just have to change the display and drag it out.

 Default xorg.conf for Xorg 1.5+ without PCI_TXT_IDS_PATH enabled.
# This file was created by VirtualBox Additions installer as it
# was unable to find any existing configuration file for X.

Section "Device"
        Identifier      "Configured Video Device"
        Driver          "vboxvideo"

Section "Screen"
    Identifier	"Default Screen"
    Monitor		"Generic Monitor"
    Device		"VirtualBox graphics card"
    DefaultDepth	24
    SubSection "Display"
      Depth	24
      Modes		"1440x900" "1280x1024" "2720x1024"
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The fullscreen display in both monitors can be easily done.
Luke Dubber managed it and it is explained here:
1 - Install VirtualBox (its free, Windows, Linux and Mac)
2 - Once you have created your virtual machine (VM) edit your settings.
3 - Go to Display section and increase the Monitor Count.
4 - Make sure to increase your Video Memory. If you don’t it won’t work (I should know, took me a bit to figure out that was my issue). I would go with the maximum 128MB if possible.
5 - Install your OS (you can do this before step 3).
6 - Make sure to install the VirtualBox guest additions.
7 - Then reboot and once you are back in you should be able to use more than one.
To read from original link Click here:
Or go to the home page of Luke Dubber

The seamless mode is something I'm battling with also and haven't seen an answer to yet.

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This should be a comment - and it should link to the actual article:… – Jon Jun 15 '15 at 3:51
While this link may answer the question, it is better to include the essential parts of the answer here and provide the link for reference. Link-only answers can become invalid if the linked page changes. – MariusMatutiae Jun 15 '15 at 5:35

As of VirtualBox 3.2.4, multiple monitor support is still only available for Windows guest operating systems. See the "Guest multi-monitor support" item in the Known Limitations chapter of the VirtualBox manual.

For Windows guests, apparently you just have to adjust the monitor count in the display settings or run in seamless mode. This post contains more details.

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