[ale] Exported Display

[hirsch at zapmedia.com]

Jeff Hubbs writes:
 > >
 > > From the ssh man page:
 > >
 > > If the ForwardX11 variable is set to ``yes'' (or, see the description 
 > > o the -X and -x options described later) and the user is using X11 
 > > (the DISPLAY environment variable is set), the connection to the X11 
 > > display is automatically forwarded to the remote side in such a way 
 > > that any X11 programs started from the shell (or command) will go 
 > > through the encrypt­ed channel, and the connection to the real X 
 > > server will be made from the local machine.  The user should not 
 > > manually set DISPLAY. Forwarding of X11 connections can be configured 
 > > on the command line or in configurationfiles.
 > >
 > Hm, can you run this past me again?  I'm not catching the reason why 
 > "The user should not manually set DISPLAY."  I do what I do basically 
 > just using ssh instead of telnet like I used to.  

If you use ssh -X, or enable it in your config file, then there is no
need to set the DISPLAY variable.  The act of sshing in will set it
appropriately.

The reason not to do it by hand is that you are apt to set it to
something like localmachinename:0 instead of remotemachinename:10.  If
you do that then your X traffic is all in the clear rather than ssh
encrypted.  It also may not work if you are behind a firewall and the
remote machine isn't.  

Even if you are clever and set it to remotemachinename:10, if someone
else ssh's in to the same machine first, you need to know to set it to
remotemachinename:11, otherwise you will end up trying to display on
this other user's desktop.

--Michael

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