Hype Blast

Home / updates

X11 forwarding request failed on channel 0

Daniel Martin |

When I do "ssh -X abcserver", I got message "X11 forwarding request failed on channel 0". I checked online and it was suggested to solve it by switching "X11UseLocalhost no" to "X11UseLocalhost yes".

However, both my manager and I don't have this administrative privilege. I am wondering, except this solution, whether there is another option to solve the issue ? I also don't have sudo privilege to directly install X11 on the server.

My local platform is:

Linux version 3.16.0-4-amd64 ()
(gcc version 4.8.4 (Debian 4.8.4-1) ) #1 SMP Debian 3.16.7-ckt25-2+deb8u3 (2016-07-02)

The remote platform is:

Linux version 3.13.0-88-generic (buildd@lgw01-16)
(gcc version 4.8.4 (Ubuntu 4.8.4-2ubuntu1~14.04.3) )
#135-Ubuntu SMP Wed Jun 8 21:10:42 UTC 2016
6

5 Answers

Adding the -v option to ssh when trying to log in will give a lot of debug information which might give a clue to exactly what the problem is, like for instance

debug1: Remote: No xauth program; cannot forward with spoofing.

which in my case installing xauth on the server fixed the issue.

1

I had to edit the sshd config file on the remote server to fix the issue. It worked on Ubuntu 16.04 Server:

$ sudo vim /etc/ssh/sshd_config
Set `X11UseLocalhost no`

Save the file.

$ sudo service sshd restart
$ exit

Now it works!

$ ssh -X user@remotehost
$ xclock
4
  1. sudo apt install xauth
  2. change the line #AddressFamily any to AddressFamily inet in /etc/ssh/sshd_config
  3. sudo service ssh restart

This is enough on Ubuntu 18.04 LTS.

After login with ssh -X (or after activating the PuTTY / KiTTY option "Enable X11 forwarding") you should see that the environment variable DISPLAY is automatically defined to localhost:10.0 or similar. After first successful login (with a functional X11 forwarding) the file .Xauthority will be generated. Another positive sign of success.

If you are interested to see and to understand the details of X11 forwarding within your session you can try with lsof -i -P|grep ssh.

2

1.make sure that during ssh -X root@server you have root permission.

2.update the /etc/ssh/sshd_config and make sure this line is uncommented

 X11Forwarding yes

3.systemctl restart sshd

4.exit from server

5.ssh -X root@server

6.virt-manager

1

In my case, as superuser, editing /etc/ssh/sshd_config on the remote host and changing the following line fixed it.

From

#X11Forwarding no

to

X11Forwarding yes

Then: pkill -HUP sshd on the remote host to make sshd reload its config, which also closes the sshd session.

1

Your Answer

Sign up or log in

Sign up using Google Sign up using Facebook Sign up using Email and Password

Post as a guest

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

You Might Also Like