Differences

This shows you the differences between two versions of the page.

--- other:x_conf [2022/08/09 17:19] – [On a Windows computer with WSL+Linux and an X server installed] jypeter
+++ other:x_conf [2024/07/10 10:54] (current) – [Using X forwarding in a Windows Powershell] jypeter
@@ Line 1: / Line 1: @@
 ====== Installing and configuring an X server ======
+<WRAP center round tip 60%>
+This detailed and easy-to-understand page will help you **set up things correctly on your own**, and help you **understand what you are doing**
+Or you can ask somebody to quickly configure everything for you, and keep on believing that things work by magic...
+</WRAP>
 ===== What is an X server? =====
@@ Line 7: / Line 15: @@
   * An //X server// **is** basically a program running on your **local** computer that understands the [[https://en.wikipedia.org/wiki/X_Window_System_core_protocol|X Windows System protocol]] used by **Linux computers** (**local** computer, or **remote** Linux servers) to generate graphics, and that can //render// (i.e. display) the graphics generated **remotely** on your **local** computer
+  * This page will mention a //''DISPLAY'' variable// several times: the X server needs this in order to know **where to display the graphics**!
 ===== What do we mean exactly with Local and Remote computers? =====
@@ Line 16: / Line 24: @@
   * The **remote computer or server** is another computer that you also want to interact with (using the screen+mouse+keyboard of your local computer)
+    * [[other:ssh#connecting_to_servers_commonly_used_by_lsce_users|Some servers used by LSCE users]]
     * We only consider on this page the case of a **remote //Linux// machine** that **requires a local running //X server//**
@@ Line 33: / Line 42: @@
 ===== Using an X server on Windows =====
-There are several available options
+There are several available X servers, and applications that will allow //X forwarding// from a remote server to your local X server
+==== Using X forwarding in a Windows Powershell ====
+**You have to type ''$env:DISPLAY = "localhost:0"'' before connecting** using ''ssh -Y remote server'' (''-X'' will not work), in order to have the ''DISPLAY'' variable correctly defined on the remote server
+<code>PS C:\> ssh -X obelix
+[...]
+ >echo $DISPLAY
+DISPLAY: Undefined variable.
+ >logout
+Connection to obelix closed.
+PS C:\> $env:DISPLAY
+PS C:\> $env:DISPLAY = "localhost:0"
+PS C:\> $env:DISPLAY
+localhost:0
+PS C:\> ssh -X obelix
+[...]
+Warning: untrusted X11 forwarding setup failed: xauth key data not generated
+[...]
+ >echo $DISPLAY
+DISPLAY: Undefined variable.
+PS C:\> ssh -Y obelix
+[...]
+Warning: No xauth data; using fake authentication data for X11 forwarding.
+[...]
+ >echo $DISPLAY
+localhost:42.0
+ >xterm&
+[1] 30038
+</code>
 ==== Installing VcXsrv ====
@@ Line 108: / Line 150: @@
 </WRAP>
+The ''XQuartz'' //X server// will be automatically started, if a graphical application needs it!
+Check the [[https://support.apple.com/guide/terminal/script-management-with-launchd-apdc6c1077b-5d5d-4d35-9c19-60f2397b2369/mac|launchd documentation]] if you need more details
+<code>$ launchctl list | grep quartz
+         -	0	org.xquartz.startx</code>
 ===== Configuration on the remote Linux server =====
@@ Line 124: / Line 171: @@
 The idea is to:
-  * Open a terminal and check that the ''DISPLAY'' environment variable is correctly defined on the local machine
+  * Open a terminal and check that the ''DISPLAY'' environment variable is defined on the local machine
     * If we use [[other:win10wsl|WSL]], we also check that we can start an application using graphics in ''WSL''
   * Connect to the remote machine
@@ Line 137: / Line 184: @@
   * ''xterm &'': the **recommended test application**. It will open a new terminal on the remote machine
   * ''xeyes &'', ''xclock &'', ''gvim &'', ''gedit &'', ''eog &'', ''evince &'', ... : other //standard// applications, that may be installed (or not)
-==== On a Linux computer ====
-Some basic commands in a terminal
+The test may fail, due to the [[other:x_conf#nothing_works|usually expected errors]]
+==== On a Linux computer or a Mac ====
+Open a //terminal// ([[other:ssh#a_recommended_terminal_for_mac|terminal on a Mac]]) and use some basic commands to check things
 <code>[Local] $ hostname
@@ Line 218: / Line 267: @@
 [Remote] $ xterm &</code>
 ===== Troubleshooting =====
 ==== Nothing works! ====
 That's unfortunate, but:
-  * Have you turned on your computer?
+  * Have you turned on your computer? :-P
-  * Do you have network access, and an account on a remote server?
+  * Do you have network access, and an account on a remote server? :-?
   * Have you run the [[other:x_conf#testing|Tests]]?
-  * Have you installed and configured the //X server// correctly? Is it really running?
+  * Have you [[other:x_conf|installed and configured the X server]] correctly? Is it really running?
   * Have you configured [[other:putty_conf|PuTTY]] and/or other required applications correctly ?
-  * Is the ''DISPLAY'' variable defined correctly on the local and remote computer?
+  * Are you [[other:x_conf#using_x_forwarding_in_a_windows_powershell|using Windows Powershell correctly]]?
+  * Is the [[other:x_conf#what_is_an_x_server|DISPLAY variable]] defined correctly on the local and remote computer?
-=== When DISPLAY is not defined correctly ===
+==== Error when there is no X server running ====
+If the ''DISPLAY'' variable is defined, but there is **no X server**, you will get a ''Can't open display: localhost://[SOME VALUE]//'' error
+<code>$ xterm &
+xterm: Xt error: Can't open display: localhost:23.0</code>
+Time to [[other:x_conf|read this page again]]...
+==== Error when there is no space left in your home directory ====
+If there is no space left in your home directory (usually the home directory of the remote server), or if you have exceeded your [[other:newppl:starting#which_disks_should_you_use|home disk quota]], you will get an error similar to [[#error_when_there_is_no_x_server_running|Error when there is no X server running]]
+<code>$ xterm &
+xterm: Xt error: Can't open display: localhost:23.0</code>
+**Solution**: clean the content of your //home//!
+==== Error when DISPLAY is not defined correctly ====
 If the ''DISPLAY'' **variable is not defined (correctly)**, you will get a ''Can't open display: //[NO VALUE DISPLAYED HERE]//'' error
@@ Line 239: / Line 313: @@
 $ echo $DISPLAY
+$ setenv DISPLAY CRAP_DISPLAY
+$ xterm
+xterm: Xt error: Can't open display: CRAP_DISPLAY
 </code>
-Make sure that you are using ''ssh -X'' or ''ssh -Y'', or that [[other:putty_conf#changing_some_useful_settings|PuTTY is configured]] with ''Enable X11 forwarding''
+  * Make sure that you are using ''ssh -X'' or ''ssh -Y'', or that [[other:putty_conf#changing_some_useful_settings|PuTTY is configured]] with ''Enable X11 forwarding''
-=== When there is no X server running ===
+  * If you use ''ssh'' in a **Windows Powershell**, read [[other:x_conf#using_x_forwarding_in_a_windows_powershell|Using X forwarding in a Windows Powershell]]
+==== Can't start a graphical application by clicking on its desktop shortcut ====
+Check the shortcut and run the command directly in a terminal to check the error message
+There is a good chance that [[other:x_conf#error_when_there_is_no_x_server_running|you have forgotten to start the X server!]]
-If the ''DISPLAY'' variable is defined, but there is **no X server**, you will get a ''Can't open display: localhost://[SOME VALUE]//'' error\\ <code>$ xterm &
-$ connect localhost port 6000: Connection refused
-xterm: Xt error: Can't open display: localhost:12.0</code>
-Time to [[other:x_conf|read this page again]]...
 ==== OpenGL related settings ====