Suppose I have a few machines, all connected to a monitor and all running linux. I want to be able do the following: Start an application on computer A and then move its window to computer B if necessary. Once the application window was moved it B should be able to use it like any other window (Similar to ssh-forwarding). Now A and B should be able to put the window back to A.

I found xpra, but I don't think this is what I need. It lets me open remote windows, but AFAIK I can't move my windows between computers.

Is there any tool out there that can do what I want? The world of X-programs is big, so there should be something.

  • 1
    From what I can tell the application needs to be started using xpra in order for you to move it while running. Did you start your application with xpra?
    – Centimane
    Commented Sep 8, 2016 at 18:05
  • @Dave I'm just reading the manpage of xpra, trying to understand the mechanisms.
    – Sirac
    Commented Sep 8, 2016 at 18:11
  • 2
    Possible duplicate of Sharing an X server (session) across computers
    – eadmaster
    Commented Mar 1, 2018 at 14:56

1 Answer 1


As Dave says, xpra is ideal for this. You need to start an xpra session on the system where your application will be run (not displayed):

xpra start :20

(20 must be a free X display number — I usually start at 20, that leaves room for multiple local X servers and incoming forwarded X sessions using SSH.)

Then you start your application on display 20:

DISPLAY=:20 myapp &

To display your application, you attach to it with xpra:

xpra attach :20

You can do this over SSH too:

xpra ssh:user@host:20

You can run multiple applications in one xpra session. xpra offers tons of possibilities, including forwarding PulseAudio, sharing the clipboard, forwarding files...

By default, attaching from one machine detaches the session from any others, so you don't need to remember to detach.

  • 1
    Ok, that sounds good. What I still miss is a way to put an window into that :20 display. I might be using firefox normally and a few minutes later I want to put it on another machine. Still, xpra already looks good, maybe it also has the final option I'm looking for, that is to open the window on computer B without B typing anything.
    – Sirac
    Commented Sep 8, 2016 at 18:58
  • AFAIK there's no way to "steal" an application from your standard X display to move it to the xpra display; you need to start it on the xpra display. Once you've done that you can move it around. If you attach to an xpra session running on A from computer B, any application added to that display will show up on B — so you can subsequently start Firefox from A on the xpra display, and it will show up on B without any action on B. Commented Sep 8, 2016 at 19:07
  • Ok, I'n beginning to like it. For now, I might xpra start :20 at startup, xpra attach :20 after that and open all exchangable programs there. I'm using i3, do you know if I can somewhere set the DISPLAY so that all my programs open up on :20?
    – Sirac
    Commented Sep 8, 2016 at 22:16
  • For completeness: Using --sharing during xpra start and xpra attach gives you the possibility to use shared sessions, although you have to test it for speed. Also, on i3 you can use i3-input -F 'exec --no-startup-id DISPLAY=:20 %s' to exec an command on display :20.
    – Sirac
    Commented Sep 9, 2016 at 1:23

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