X11 Forwarding: GUI appears in the remote server instead of client

Question

I have two machines, PC1 and PC2. in PC1 I have Msys2 and Xming installed on Windows 7 while in the second machine PC2 I have Windows 10 with Ubuntu 18.04 on WSL (Windows Subsystem for Linux), Xming is also installed. I configured both machines to use ssh and the necessary configurations for X11 forwarding in (/etc/ssh/sshd_config). in PC1 I have also to set DISPLAY variable:

export DISPLAY=localhost:0

I want to ssh from PC1 to PC2 but I have one problem: The following command works fine:

ssh -Y username@PC2 gedit

it shows gedit on PC1 as expected. But when I ssh to PC2 then I start gedit:

$ ssh -Y username@PC2  # Now I am logged in to PC2
$ gedit

The GUI appears in PC2 instead of PC1

Could you please explain what's going wrong with the second way?

You pretty much never need to set `DISPLAY` manually. And if you have a configuration file which replaces a correct `DISPLAY` variable with an incorrect one you have set manually, it can cause things to break. — kasperd, Jun 02 '18 at 23:21
@Ignacio In PC2 (ubuntu 18.04 on wsl with xming, DISPLAY=:0) — s.ouchene, Jun 03 '18 at 00:26
@kasperd : the DISPLAY variable sometimes must be set in my case if it is not set the GUI doesn't appear — s.ouchene, Jun 03 '18 at 00:31
And that's why it displays on PC2. You need to let sshd set `$DISPLAY` appropriately. — Ignacio Vazquez-Abrams, Jun 03 '18 at 00:33
@Ignacio: in PC2 when I installed Xming I added `export DISPLAY=:0` in `~/.bashrc` to be able to use Xming — s.ouchene, Jun 03 '18 at 00:37
That's nice and all, but it's interfering with showing the GUI on PC1. — Ignacio Vazquez-Abrams, Jun 03 '18 at 00:38
@Navaro That line is your problem. You shouldn't have put it there in the first place. — kasperd, Jun 03 '18 at 07:10
@IgnacioVazquez-Abrams & @kasperd: Thank you very much, I solved that by removing `export DISPLAY=:0` from PC2 `.bashrc`. In PC1, before connecting, I have to `export DISPLAY=localhost:0`. That solves the problem. — s.ouchene, Jun 03 '18 at 08:35

score 3 · Accepted Answer · answered Jun 03 '18 at 17:58

3

X forwarding over SSH is dependent on sshd setting the value of $DISPLAY appropriately, so forcing an override on the remote system will interfere. If you must set it regardless then only set it if it doesn't already have a value:

: ${DISPLAY:=:0}

answered Jun 03 '18 at 17:58

Ignacio Vazquez-Abrams

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X11 Forwarding: GUI appears in the remote server instead of client

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