Remote x-server with ssh -X

Question

I am trying to start a remote gnome session using: ssh -X [email protected] gnome-session

Both client and server are Ubuntu version 12.04

I get the following (and not a lot happens)...

GNOME_KEYRING_CONTROL=/tmp/keyring-3aeNAh
GPG_AGENT_INFO=/tmp/keyring-3aeNAh/gpg:0:1
GNOME_KEYRING_PID=3573
GNOME_KEYRING_CONTROL=/tmp/keyring-3aeNAh
GPG_AGENT_INFO=/tmp/keyring-3aeNAh/gpg:0:1
GNOME_KEYRING_CONTROL=/tmp/keyring-3aeNAh
GPG_AGENT_INFO=/tmp/keyring-3aeNAh/gpg:0:1
SSH_AUTH_SOCK=/tmp/keyring-3aeNAh/ssh
GNOME_KEYRING_CONTROL=/tmp/keyring-3aeNAh
GPG_AGENT_INFO=/tmp/keyring-3aeNAh/gpg:0:1
SSH_AUTH_SOCK=/tmp/keyring-3aeNAh/ssh

(gnome-settings-daemon:3572): color-plugin-WARNING **: failed to get contents of /sys/class/dmi/id/board_version: Failed to open file '/sys/class/dmi/id/board_version': No such file or directory

** (gnome-settings-daemon:3572): WARNING **: You can only run one xsettings manager at a time; exiting

** (gnome-settings-daemon:3572): WARNING **: Unable to start xsettings manager: Could not initialize xsettings manager.
compiz (core) - Error: Screen 0 on display "localhost:10.0" already has a window manager; try using the --replace option to replace the current window manager.
Initializing nautilus-gdu extension
Created new window in existing browser session.
** Message: applet now removed from the notification area
** Message: using fallback from indicator to GtkStatusIcon

(gnome-settings-daemon:3572): keyboard-plugin-WARNING **: Failed to set the keyboard layouts: GDBus.Error:org.freedesktop.Accounts.Error.PermissionDenied: Not authorized

** (gnome-settings-daemon:3572): WARNING **: Failed to connect context: Connection refused

(gnome-settings-daemon:3572): clipboard-plugin-WARNING **: Clipboard manager is already running.

(gnome-settings-daemon:3572): color-plugin-WARNING **: failed to create device: GDBus.Error:org.freedesktop.ColorManager.Failed: failed to obtain org.freedesktop.color-manager.create-device auth

(gnome-settings-daemon:3572): color-plugin-WARNING **: GDBus.Error:org.freedesktop.ColorManager.Failed: failed to obtain org.freedesktop.color-manager.create-profile auth

(gnome-settings-daemon:3572): color-plugin-WARNING **: no xrandr-Samsung Electric Company-SAMSUNG device found: Failed to find output xrandr-Samsung Electric Company-SAMSUNG
Shutting down nautilus-gdu extension

** (gnome-settings-daemon:3572): WARNING **: Failed to connect context: Connection refused
Connection failure: Connection refused
pa_context_connect() failed: Connection refused

Solution

I assume that what you are trying to do is start a complete remote Gnome session displaying on your local machine. This fails because you already have a local session manager controlling your X server display.

Your options are:

1. Simply start individual remote applications using ssh -X [email protected] xclock

2. Assuming XDMCP is enabled on the remote machine...

   2a. Use Xnest -query 192.168.1.107 -geometry 1024x768 :1 to start a remote login session in a local window.

   2b. Use Xephyr :1 -screen 1024x768 -query 192.168.1.107 which is a better X server than Xnest

3. Also assuming XDMCP on the remote machine, configure your local machine to use the XDMCP chooser instead of the standard greeter on startup.

Enabling XDMCP is simply a case of putting

[xdmcp]
Enable=true

in /etc/gdm/custom.conf and restarting gdm or rebooting (assuming you are running gdm).

If you only intend to run a few applications remotely, then option 1 is simplest and continues to use SSH encrypted traffic, which none of the others do (so they are best only used on a trusted local network).

If you need to so something more complicated, then 2b (Xephyr) is may be better, but I've usually found just using ssh -X ... & for multiple remote applications to be adequate.

If you are doing everything remotely, i.e. the local machine is just a display server and doesn't do anything itself, then you need to look into using option 3, starting the XDMCP chooser instead of the standard login.

---

PS: As noted in the comments, both Xnest and Xephyr are applications which handle the X server protocol and put the entire session into a window. Xnest uses the functions provided by the local X server while Xephyr handles much more of the server protocol itself so is more robust. They may not be installed by default because the average user wouldn't use them.

---

PPS: After a little thought it's obvious how to encrypt a Xephyr or Xnest session...

ssh -X [email protected] Xephyr :1 -query localhost -screen 1280x1024

Comments

[Admin]

If you want to play around, I entered an answer with some tips for using basic ssh from a commandline, including generating a key and copying it to the remote host. Once you learn to use ssh, you might be surprised at how much can be done using it.

[Deepak Verma]

Might be useful to indicate what Xnest/Xephyr do and why, since they aren't installed by default, I don't think. I've never found any need to use xdmcp, so I have no idea myself. I use simple ssh -Y from a terminal, then run what I need from there.

[ish]

@MartyFried: It looks like both are X servers which can run in a window. It looks like the user wants to X-forward an entire session/display. Personally I'd just use VNC, which creates a new display on the existing X server and save myself the headache.

[Deepak Verma]

@izx: I've used VNC in the past for Windows systems, but with two Ubuntu systems, I usually like the built-in ssh, although sometimes I get confused when running GUI apps, as it's hard to differentiate local vs remote apps. But for what I do (mostly editing from or administering a server), it seems to work the best.

[StarNamer]

@MartyFried The downside of VNC is that you are simply controlling the remote machine's display. So you can't have one user logged in on that display with another user connected remotely. The XDMCP solutions crate completely separate sessions allowing 2 or more users to use the same machine.

[benlad]

Your 2b solution worked a treat. I did try the ssh version, but had an issue about ssh keys. The message is too long to post here. I'll use the method that works for now.

[Jasper Blues]

On OSX to ubuntu I'm just getting a black screen. . will post a separate question based on error logs, I guess.

[artfulrobot]

Suggested edit: If using lightdm instead of gdm then enable XDMCP in /etc/lightdm/lightdm.conf by adding [XDMCPServer]¶enabled=true where ¶ means new line