putty vs. ssh -X (why different $DISPLAY needed)

musthero · 02-18-2009, 03:50 PM

Hi guys,

I use one remote machine which I want to be connected to.
I use putty to connect to it and it works if I specify DISPLAY variable

export DISPLAY=my_ip_address:0.0

but if I use my linux desktop to connect to remote machine (ssh -X ...) this way of specifying DISPLAY variable does not work anymore, BUT if I define DISPLAY as follows

export DISPLAY=localhost:13.0

it works!
What is the difference? Why it happens? (the remote machine is same in both cases)

Thanks for any help!

acid_kewpie · 02-18-2009, 04:44 PM

well the X tunneling over ssh should be set up automatic, and i'm not sure why you're having to set that like you are, but the difference is the tunneling itself. you can run the first type under ssh and it *should* work, no reason why not if it does on putty. what if you DON'T do X tunneling?

musthero · 02-19-2009, 12:40 AM

Quote:

Originally Posted by acid_kewpie

well the X tunneling over ssh should be set up automatic, and i'm not sure why you're having to set that like you are, but the difference is the tunneling itself. you can run the first type under ssh and it *should* work, no reason why not if it does on putty. what if you DON'T do X tunneling?

Yes, that's true. If I use ssh -X ... it sets up $DISPLAY automatically but it's not the case with putty where after connection is established $DISPLAY is empty so I need to define it. If I define it as localhost:13.0 it does not work for putty but works for ssh -X in linux

acid_kewpie · 02-19-2009, 01:35 AM

well yes, again that is X forwarding over ssh. putty doesn't do this at all. you setting $DISPLAY in putty is the same as being local to the box and setting it, making X clients connect to any arbitrary server, it's nothing to do with ssh at all. With ssh -X it is, and the X connections are *inside* the ssh tcp connection across the network.

musthero · 02-19-2009, 07:41 PM

Quote:

Originally Posted by acid_kewpie

well yes, again that is X forwarding over ssh. putty doesn't do this at all. you setting $DISPLAY in putty is the same as being local to the box and setting it, making X clients connect to any arbitrary server, it's nothing to do with ssh at all. With ssh -X it is, and the X connections are *inside* the ssh tcp connection across the network.

Yes, it makes sense. Although I do X11 forwarding in putty v0.60 it works perfectly without it! So it seems that this option does not do anything, and it's not equivalent to -X option in ssh as I though before. Putty just doesn't do what it's supposed to, meaning does not do X11 over ssh with X11 forwarding option checked. That's intresting!

Will play with it again...
Thanks for helping me to understand that!