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03/06/2019

X11 forwarding request failed on channel 0 Error and Solution



I am a new Linux server user. I need to tunnel X over ssh. I type the following command from OS X Unix terminal to login into far_away_machine (a centos server):

ssh -X -o options -A -p 22 user@centos-far-away-server

But, I am getting the following error on screen:

X11 forwarding request failed on channel 0
Last login: Sun Mar 23 15:58:51 2014 from 1.2.3.4

How do I fix “X11 forwarding request failed on channel 0” on Linux or Unix-like systems?

[donotprint][/donotprint]You may get an error when you try to display a server managment app or any other X app. You will be able to run a graphical application on server and get applications display (window) on your desktop using X11 forwarding. The fix this issue make sure OpenSSH SSHD is configured as follows

Fixing forwarding request failed on channel 0 on a Linux/Unix based server

Login to your centos-far-away-server, enter:
$ ssh -A -p 22 user@centos-far-away-server
Edit /etc/ssh/sshd_config file, enter:
$ sudo vi /etc/ssh/sshd_config
Set the following two options:

X11Forwarding yes
X11UseLocalhost no

Save and close the file. Reload the sshd, enter:
$ sudo /etc/init.d/sshd reload
Sample outputs:

Reloading sshd:                                            [  OK  ]

Install X authority file utility

You need to install xauth tool using yum command:
$ sudo yum install xauth
Sample outputs:

Loaded plugins: downloadonly, fastestmirror, security
Loading mirror speeds from cached hostfile
 * base: mirrors.tummy.com
 * epel: mirror.steadfast.net
 * extras: centos-mirror.jchost.net
 * updates: centos.hostingxtreme.com
Setting up Install Process
Resolving Dependencies
--> Running transaction check
---> Package xorg-x11-xauth.x86_64 1:1.0.2-7.1.el6 will be installed
--> Processing Dependency: libXmuu.so.1()(64bit) for package: 1:xorg-x11-xauth-1.0.2-7.1.el6.x86_64
--> Running transaction check
---> Package libXmu.x86_64 0:1.1.1-2.el6 will be installed
--> Processing Dependency: libXt.so.6()(64bit) for package: libXmu-1.1.1-2.el6.x86_64
--> Running transaction check
---> Package libXt.x86_64 0:1.1.3-1.el6 will be installed
--> Finished Dependency Resolution
 
Dependencies Resolved
 
===========================================================================================================
 Package                      Arch                 Version                        Repository          Size
===========================================================================================================
Installing:
 xorg-x11-xauth               x86_64               1:1.0.2-7.1.el6                base                35 k
Installing for dependencies:
 libXmu                       x86_64               1.1.1-2.el6                    base                66 k
 libXt                        x86_64               1.1.3-1.el6                    base               184 k
 
Transaction Summary
===========================================================================================================
Install       3 Package(s)
 
Total download size: 285 k
Installed size: 681 k
Is this ok [y/N]: y
Downloading Packages:
(1/3): libXmu-1.1.1-2.el6.x86_64.rpm                                                |  66 kB     00:00     
(2/3): libXt-1.1.3-1.el6.x86_64.rpm                                                 | 184 kB     00:00     
(3/3): xorg-x11-xauth-1.0.2-7.1.el6.x86_64.rpm                                      |  35 kB     00:00     
-----------------------------------------------------------------------------------------------------------
Total                                                                      1.2 MB/s | 285 kB     00:00     
Running rpm_check_debug
Running Transaction Test
Transaction Test Succeeded
Running Transaction
  Installing : libXt-1.1.3-1.el6.x86_64                                                                1/3 
  Installing : libXmu-1.1.1-2.el6.x86_64                                                               2/3 
  Installing : 1:xorg-x11-xauth-1.0.2-7.1.el6.x86_64                                                   3/3 
  Verifying  : libXmu-1.1.1-2.el6.x86_64                                                               1/3 
  Verifying  : libXt-1.1.3-1.el6.x86_64                                                                2/3 
  Verifying  : 1:xorg-x11-xauth-1.0.2-7.1.el6.x86_64                                                   3/3 
 
Installed:
  xorg-x11-xauth.x86_64 1:1.0.2-7.1.el6                                                                    
 
Dependency Installed:
  libXmu.x86_64 0:1.1.1-2.el6                          libXt.x86_64 0:1.1.3-1.el6                         
 
Complete!

Try ssh command as follows:
$ ssh -X -o options -A -p 22 user@centos-far-away-server
Sample outputs:

Last login: Sun Mar 23 16:25:09 2014 from 1.2.3.4
/usr/bin/xauth:  creating new authority file /home/vivek/.Xauthority

Once you got ~/.Xauthority file, you can run X apps as follows over ssh:
$ xeyes &
$ my-cool-raid-app-manager &

Tip: Finding issues with X over ssh

If you still need hints, run ssh command as follows to debug problems:
$ ssh -v user@server-name-here

Posted by: SXI ADMIN

The author is the creator of nixCraft and a seasoned sysadmin, DevOps engineer, and a trainer for the Linux operating system/Unix shell scripting. Get the latest tutorials on SysAdmin, Linux/Unix and open source topics via RSS/XML feed or weekly email newsletter.

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