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Here's what I need to do. I need to be playing a movie over HDMI to a television screen for my friends while I'm hacking on some personal projects over VGA to a smaller monitor. It's imperative that the screens be separate, as I have a work monitor application running on the VGA screen which will be taking screenshots at random and it'd be nice to not have the screenshots be half Megamind and half Eclipse. I've heard that you can run a different X session on each screen, but I don't know how to do it. Essentially, I need VLC in fullscreen on one screen and my full desktop environment on the other. I'm running Linux Mint 11 (Ubuntu 11.04) 64bit.

Is there a way to do this? If so, could I make it so I could switch the X session my mouse is associated with in order to control the movie?

Naftuli Kay
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2 Answers2

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What you want is a multiseat Xxorg configuration. I don't know which distro you're using, so I'll just link to the xorg Wiki entry. X is well suited for this, since 20+ years ago many institutions did this with all of their Unix machines.

One limitation: You won't be able to use the same keyboard and mouse for both displays.

Chris Stryczynski
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Klox
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  • I've edited the question above to include my distro: Linux Mint 11/Ubuntu 11.04 64bit. Will I be able to at the least use a terminal to interface with the other display? – Naftuli Kay Aug 24 '11 at 19:25
  • The xorg Wiki links to this Ubuntu page: https://help.ubuntu.com/community/MultiseatX I'm not sure what you're thinking of when you mention interfacing the other display, but if you want to control VLC from your other X server, you could use the VLC HTTP control interface (or another VLC control interface): http://www.videolan.org/doc/play-howto/en/ch04.html#id590873 – Klox Aug 24 '11 at 19:51
  • So, essentially `export DISPLAY=:2 && vlc myfile` would start VLC on the other screen, then I could use the HTTP plugin to control it. Makes sense. I'll see if I can get something working here. – Naftuli Kay Aug 24 '11 at 20:16
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    Not true on the keyboard and mouse issue. You can use `synergy` to use the same keyboard and mouse across multi-seat X displays either on the same machine or even network machines. – Caleb Aug 24 '11 at 20:55
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    @TK: Shorter command that also does what you want, without the side effect you probably don't want: `DISPLAY=:2 vlc myfile`. This changes the DISPLAY variable for the `vlc` command only, without stomping on the starting shell's DISPLAY variable. This is even more useful if you background VLC so you can keep using that terminal window. – Warren Young Aug 24 '11 at 21:14
  • Winning! Is there a way to start the separate X server without having to keep logging out? It'd be nice to be able to keep things going without having to keep rebooting or killing the main X. I only need to do this setup once, I won't be using multihead often after today. – Naftuli Kay Aug 24 '11 at 21:16
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I just wrote a quick little tip on how to set up and run separate xsessions on 2 monitors. Check it out http://www.nu2upc.com/linux-tips/configuring-dual-displays/

First let me explain what I am going to accomplish to see if this meets your needs. I am going to be running 2 monitors, 1 is connected via VGA and the other by DVI. The VGA monitor is to be connected to screen 0 as monitor 0 on xsession 0, and the DVI being on 1.

Problem that I ran into is that the system was automatically assigning 0 to the DVI monitor therefore not giving me the results that I desired.

Solution was to simply unplug the DVI monitor, reboot and start with a clean xorg.conf file. I opened up nvidia-settings checked to see that my VGA monitor was configured the way I wanted, then I plugged in my DVI monitor, clicked on “X Server Display Configuration” then “Detect Displays” and it found the DVI monitor. I then set DVI monitor to be right of my VGA monitor and clicked on “Configure” and selected “Separate X Screen” then ensured that all other settings were as I like. I clicked on “Save X Configuration File” and said yes to merge the changes. Then I rebooted my system. and viola! I now have my 2 displays running each in a separate xsessions!

Léo Lam
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Chuq
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