From b15cb324ab9e3f292bf079fc9b5d3ec4a27e8f70 Mon Sep 17 00:00:00 2001
From: Pavel Jirasek <pavel.jirasek@vsb.cz>
Date: Thu, 28 Jun 2018 13:53:23 +0200
Subject: [PATCH] Tip

---
 .../graphical-user-interface/x-window-system.md            | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/docs.it4i/general/accessing-the-clusters/graphical-user-interface/x-window-system.md b/docs.it4i/general/accessing-the-clusters/graphical-user-interface/x-window-system.md
index e6f4756b5..2b3809ad5 100644
--- a/docs.it4i/general/accessing-the-clusters/graphical-user-interface/x-window-system.md
+++ b/docs.it4i/general/accessing-the-clusters/graphical-user-interface/x-window-system.md
@@ -28,10 +28,15 @@ Then log in as usual.
 In order to display graphical user interface GUI of various software tools, you need to enable the X display forwarding. Log in using the -X option in ssh client:
 
 ```console
- local $ export DISPLAY=localhost:0.0
  local $ ssh -X username@cluster-name.it4i.cz
 ```
 
+!!! tip
+    If unable to execute graphical sofware showing error message "cannot open display" then try export DISPLAY variable before log in using the -X option in ssh client:
+```console
+ local $ export DISPLAY=localhost:0.0
+```
+
 ## Verify the Forwarding
 
 To verify the forwarding, type
-- 
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