I'm able to login to sever using

ssh -X Hostip

but when i run the command xclock it give me this error

Error: Can't open display: localhost:11.0

I check my Display value using

echo $DISPLAY

and the result is

localhost:11.0

And X11 forwarding is set to YES in sshd_config file

X11Forwarding yes
X11DisplayOffset 10
X11UseLocalhost yes

Any advice what I'm missing here?

  • 2
    Have you tried -Y instead of -X? – Flup Jul 22 '13 at 11:35
  • 2
    Also, make sure you understand the implications of using -Y instead of -X. You may also want to look at xhost. – a CVn Jul 22 '13 at 11:36
  • 1
    For RedHat/CentOS 7 (at least), you need the xorg-x11-xauth package, as per my answer here: unix.stackexchange.com/questions/138936/… – Mike S Apr 22 '16 at 20:12

Use -Y. From the man page on ssh:

-Y Enables trusted X11 forwarding. Trusted X11 forwardings are not subjected to the X11 SECURITY extension controls.

If you're still having problems though, you can try setting $DISPLAY to your local box's IP:

$ export DISPLAY='<ip_address>:11.0'

It may work to set it as

$ export DISPLAY='127.0.0.1:11.0'

People seem to have this problem commonly when ssh'ing from Mac OS X. You may also want to set

X11UseLocalhost no

in this case as well.

  • 1
    Using XQuartz I was unable to use the -Y flag. "X11 connection rejected because of wrong authentication." – Erik Feb 21 '14 at 4:01
  • 2
    even after trying your other suggestions, I'm unable to open a display. – Erik Feb 21 '14 at 4:04
  • 1
    Neither one of these worked for me either. I needed to install XWindow support in my Centos 7 server (minimal) with: yum groupinstall "X Window System" -y – Mark Edington Dec 29 '15 at 16:19
  • @MarkEdington this is because RedHat/CentOS require the xorg-x11-xauth package, as per my answer here: unix.stackexchange.com/questions/138936/… – Mike S Apr 22 '16 at 20:11

Credit to https://unix.stackexchange.com/a/12772/61349 for their diagnostic instructions.

Ensure you're ssh client is requesting X11 Forwarding with the -v flag

ssh example.com -X -v

And look for thespecific message:

debug1: Requesting X11 forwarding with authentication spoofing.

Another telltail problem sign is the lack of the DISPLAY environment variable beign set for you. If its blank/unset, there is something wrong. At least according to the same post credited above, these variables are set for you automatically.


I was using an SSH Control Master my ssh connections like so:

Host <hostname>
    ControlMaster auto
    ControlPath ~/.ssh/control/%r@%h:%p
    ControlPersist 10m

My earlier ssh connection did not request X11Firwarding, therefore future ssh call's options weren't being used. So for me,

ssh -X was just being ignored altogether

If you aren't seeing "Requesting X11 Forwarding", but you do see the muxer reusing sessions;

debug1: auto-mux: Trying existing master
debug1: mux_client_request_session: master session id: 10

Then you need to exit your current ControlMaster for that connection and reconnect with the -X/-Y flag.

To Stop your ControlMaster

ssh -O check <hostname>

Master running (pid=2758)

(This will exit all active connections using the ControlMaster)

ssh -O exit <hostname>

Exit request sent.

this worked for me:

Change

X11UseLocalhost yes

to

X11UseLocalhost no
  • Thanks, Don. that worked for me also. I gave you an upvote. I believe the problem interfering with the default was that the specific machine is xhost enabled. – L. D. James Dec 22 '15 at 0:21
  • 5
    on guest? host? which configuration file? thx to complete your answer – Philippe Gachoud Jul 20 '16 at 8:22

When trying to forward to XQuartz on macOS, I fixed the issue by running the ssh command (ssh -Y in my case) from the XQuartz terminal (opened by right-clicking the XQuartz icon in the dock and clicking Applications > Terminal).

What fixed this for me is simply installing xauth, once done it worked like a charm!

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