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We are using Oracle Secure Global desktop to provide remote access to the Solaris desktop. It sets the DISPLAY variable to unix:10.0.

It seems to be working as if the DISPLAY was set to localhost:10.0. What does "unix" mean here?

Is it a common usage or something specific to SGD? As far as I know, usually DISPLAY is set in the form [hostname or IP]:[screen].

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Looks to me like unix just might be the hostname of the computer X11 is sending it's display to. –  maxmackie Sep 9 '11 at 14:43

1 Answer 1

It's reasonably common to see this. It means "use a unix-domain socket" instead of a TCP/IP socket. These "unix domain" sockets show up in the file system. For instance, on my old Slackware 11.0 system, the Unix domain socket has the file name /tmp/.X11-unix/X0

12 % ls -ltr /tmp/.X11-unix
total 0
srwxrwxrwx 1 root users 0 2011-07-19 18:07 X0=

Note the 's' in the mode: that's "socket". I seem to recall other X11s putting the unix-domain socket in /tmp/ directly.

Using a unix-domain socket for X11 traffic can be quite a bit faster, and probably a lot more secure than flinging the traffic over TCP-IP

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Shouldn't it be unix/:10 then? The format is [transport/]host:[:]server[.screen], with host blank for local. (The extra optional : is to support the old method for differentiating tcp from decnet) –  Random832 Sep 9 '11 at 16:33
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@Random832 I'm not sure what the exact syntax is, but X.org Xlib accepts unix:0 as a synonym of unix/:0. –  Gilles Sep 9 '11 at 23:46
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To add to this answer: using a unix socket means that the X server and the client are running on the same machine. Under most modern X implementations, this allows the client and the server to operate via shared memory instead of via network-style messages. Shared memory enables many optimisations, which are especially important when viewing video or drawing 3D images. –  Gilles Sep 9 '11 at 23:48
    
@Gilles Is this documented anywhere? I went and looked up the source (what I thought was the source), since the format wasn't well-documented, and it doesn't seem to support this being a synonym –  Random832 Sep 10 '11 at 2:39
    
I was under the impression that those optimisations are triggered whenever the local host is used as a display server, even if TCP is used. I remember reading this in some manual back in the XFree86 days. –  Alexios May 2 '12 at 6:55

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