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?

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

am a new Linux server user. I need to tunnel X over ssh. I type the following command on a CentOS/RHEL based remote host to get display on a local desktop:

ssh -X user@server1.cyberciti.biz

xeyes &

firefox &

But, I am getting an error that read as follows:

**error**: Failed to contact configuration server; some possible causes are that you need to enable TCP/IP networking for ORBit, or you have stale NFS locks due to a system crash. See http://projects.gnome.org/gconf/ for information. (Details – 1: Failed to get connection to session: /bin/dbus-launch terminated abnormally without any error message)

How do I fix this error on a newly formatted/installed RHEL or CentOS Linux 6.x server?

You need to install D-Bus. It is nothing but a message bus system, a simple way for applications to talk to one another. In addition to interprocess communication, D-Bus helps coordinate process lifecycle; it makes it simple and reliable to code a “single instance” application or daemon, and to launch applications and daemons on demand when their services are needed. You also need to install Fonts on a CentOS/RHEL based system.

To fix /bin/dbus-launch terminated abnormally without any error message on a CentOS/RHEL

Type the following yum command to install D-Bus and Fonts:

$ sudo yum install dbus-x11

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 dbus-x11.x86_64 1:1.2.24-7.el6_3 will be installed

–> Finished Dependency Resolution

Dependencies Resolved

===========================================================================================================

Package                 Arch                  Version                           Repository           Size

===========================================================================================================

Installing:

dbus-x11                x86_64                1:1.2.24-7.el6_3                  base                 40 k

Transaction Summary

===========================================================================================================

Install       1 Package(s)

Total download size: 40 k

Installed size: 28 k

Is this ok [y/N]: y

Downloading Packages:

dbus-x11-1.2.24-7.el6_3.x86_64.rpm                                                  |  40 kB     00:00

Running rpm_check_debug

Running Transaction Test

Transaction Test Succeeded

Running Transaction

Installing : 1:dbus-x11-1.2.24-7.el6_3.x86_64                                                        1/1

Verifying  : 1:dbus-x11-1.2.24-7.el6_3.x86_64                                                        1/1

Installed:

dbus-x11.x86_64 1:1.2.24-7.el6_3

Complete!

To install Fonts, type:

$ sudo yum groupinstall  Fonts

Now, you can run and tunnel X over ssh:

$ ssh -X user@server1.cyberciti.biz

$ xeyes

$ firefox

‘m installing FreeBSD 10 Xorg and xfce4 desktop. But, getting the following error:

(EE) Failed to load module “fbdev” (module does not exist, 0)

How do I fix this problem on FreeBSD 10 amd64 based system?

You need to install the X.Org xf86-video-fbdev driver. This can be installed using either ports or binary package using the pkg command.

Fixing (EE) Failed to load module “fbdev” (module does not exist, 0) on a FreeBSD Xorg

Open the Terminal app and login as root user using su – command:

su –

Install the xf86-video-fbdev via the port

Type the following command:

# cd /usr/ports/x11-drivers/xf86-video-fbdev/

# make install clean

Install the xf86-video-fbdev via the binary package

Type the following command:

# pkg install x11-drivers/xf86-video-fbdev

OR

# pkg install xf86-video-fbdev

Sample outputs:

Updating repository catalogue

The following 1 packages will be installed:

Installing xf86-video-fbdev: 0.4.4_4

The installation will require 28 KB more space

11 KB to be downloaded

Proceed with installing packages [y/N]: y

xf86-video-fbdev-0.4.4_4.txz        100%   11KB  11.1KB/s  11.1KB/s   00:00

Checking integrity… done

[1/1] Installing xf86-video-fbdev-0.4.4_4… done

Test new Xorg config

First, create an Xorg config file:

# Xorg -configure

This will generate a file named /root/xorg.conf.new which attempts to load the proper drivers for the detected hardware. Next, test that the automatically generated configuration file works with the graphics hardware by typing:

# Xorg -config xorg.conf.new -retro

If the test is successful, copy the configuration file to /etc/X11/xorg.conf:

# cp xorg.conf.new /etc/X11/xorg.conf

References

FreeBSD handbook: Chapter 6. The X Window System