ssh -X X11 forwarding doesn't work

[Seth Arnold]

Trying to use evince over X11 forwarding via ssh -X:

$ ssh -X sec-xenial-amd64 evince sp800-38a.pdf
Failed to connect to Mir: Failed to connect to server socket: No such file or directory
Unable to init server: Could not connect: Connection refused
Cannot parse arguments: Cannot open display:

Client is running 14.04 LTS, unity7 desktop.
Server is running a recent Xenial.

Thanks

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: evince 3.18.2-1ubuntu4
ProcVersionSignature: User Name 4.4.0-16.32-generic 4.4.6
Uname: Linux 4.4.0-16-generic x86_64
ApportVersion: 2.20.1-0ubuntu2
Architecture: amd64
Date: Thu Apr 21 16:15:17 2016
InstallationDate: Installed on 2016-02-11 (70 days ago)
InstallationMedia: Ubuntu 16.04 LTS "Xenial Xerus" - Alpha amd64 (20160210)
ProcEnviron:
 TERM=rxvt-unicode
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: evince
UpgradeStatus: No upgrade log present (probably fresh install)

[Sebastien Bacher (seb128)]

Does it work if you set the DISPLAY env to something?

[Sebastien Bacher (seb128)]

oh, also does it work for other gtk softwares?

(doing a simple ssh -X localhost evince on a xenial system works fine here)

[Alan Mimms (alanm-unforgettable)]

I can use one machine to start an X11 forwarded client on another. I did this to start gnome-terminal on a Ubuntu Server 16.04 from a Kubuntu 16.04 desktop by using

  ssh -Y -f 192.168.0.89 gnome-terminal

This works. Then I look at that gnome-terminal's environment and DISPLAY and SSH_CLIENT variables are properly set:

  DISPLAY=localhost:10.0
  SSH_CLIENT=192.168.0.215 38634 22

Then I look for listeners on TCP port #6010 as is implied by the above DISPLAY envar:

  $ netstat -anl4
  Active Internet connections (servers and established)
  Proto Recv-Q Send-Q Local Address Foreign Address State
  tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN
  tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN
  tcp 0 0 192.168.0.84:22 192.168.0.215:38542 ESTABLISHED
  tcp 0 0 192.168.0.84:22 192.168.0.215:36110 ESTABLISHED
  udp 0 0 0.0.0.0:68 0.0.0.0:*

No such listener. I did this same sort of ssh connection from my desktop Kubuntu to a Raspberry Pi running Raspbian and the rpi has a listener as I would expect it to.

I believe this lack of a listener for the ssh on the remote machine to allow X11 clients to connect back to the server through "screen :10" is what is missing.

In in /etc/ssh/sshd_config on the target Ubuntu 16.04 server machine I have this for X11 forwarding configuration:

  $ cat /etc/ssh/sshd_config | grep -i x11
  X11Forwarding yes
  X11DisplayOffset 10

I have always been able to get this to work with previous Ubuntu releases (14.04, the 15.x series, etc.). This is something specific to changes in Xenial. It looks like the release notes (https://launchpad.net/ubuntu/xenial/+source/openssh/+changelog) include some changes for this area of ssh. Maybe the fix for this (http://www.openssh.com/txt/x11fwd.adv) partially borked ssh's X11 forwarding mechanism?

[Alan Mimms (alanm-unforgettable)]

I just re-read the originator report for this bug. My problem is not exactly the same as his in that I DO get a X11 forwarded client to work but I cannot connect any more of them except through additional X11 forwarded ssh commands from the original client. Should I report this as a separate bug? I think it might be distinct.

[Launchpad Janitor (janitor)]

[Expired for evince (Ubuntu) because there has been no activity for 60 days.]